Stem cell model offers first glimpse of early human embryonic development

It's one of life's most defining moments -- that crucial step in embryonic development, when an indistinct ball of cells rearranges itself into the orderly three-layered structure that sets the stage for all to come. Known as gastrulation, this crucial process unfolds in the third week of human development. "Gastrulation is the origin of our own individualization, the emergence of our axis," says Rockefeller's Ali Brivanlou. "It is the first moment that separates our heads from our behinds."

Observing the molecular underpinnings of this pivotal event would go a long way toward helping scientists prevent miscarriages and developmental disorders. But studying human gastrulation has proven both technologically difficult and ethically complicated, and thus current approaches have had limited success in expanding our understanding of early human development. Now Brivanlou and colleagues have demonstrated how a stem cell model system known as a blastoid can allow the study of the nuances of human gastrulation in the presence of pre-implantation extra-embryonic cell types. Their study, published in Stem Cell Reports, describes the scientific and clinical potential of this new platform.

"Gastrulation was a tremendous black box. We had never seen ourselves at that stage," Brivanlou says. "This moves us closer to understanding how we begin."

A better blastocyst

Prior to implantation, an embryo is a ball of about 250 cells organized as a blastocyst. This elusive ball of cells was difficult to study directly, so scientists developed blastoids -- stem-cell-based blastocyst models. Blastoids can be cloned, experimentally manipulated, and programmed, allowing scientists to study identical blastoids over and over again.

The question was whether blastoids could gastrulate in vitro. Unlike a blastocyst in vivo, which rolls around in the uterus until it attaches to maternal tissue, blastoids were good at modeling the ball of cells from which life emerges, but it remained unclear whether this in vitro model could model later stages of human development. That is, until Brivanlou developed a platform to allow blastoids to attach in vitro, and thereby progress toward gastrulation.

"We were then able to see epiblast symmetry breaking, marked by BRA expression, for the first time with the high molecular resolution," says Riccardo De Santis, a research associate in the Brivanlou lab and lead author on the study. "This allowed us to start asking more detailed questions about the earliest moments of life."

With this unprecedented clarity, the team directly observed two key moments in gastrulation: the first epiblast symmetry-breaking event and the emergence of the molecular markers of the primitive streak and mesoderm upon in vitro attachment.

The primitive streak is a structure that marks the beginning of gastrulation and lays the foundation for the three primary layers of the embryo. One of those layers, the mesoderm, forms during gastrulation and gives rise to muscles, bones, and the circulatory system. The team discovered that, as early as seven days after attachment, they were already able to use molecular markers to detect the earliest signature of a nascent primitive streak and mesodermal cells.

To confirm their findings, the team also compared the blastoid results with data from in vitro attached human embryos and demonstrated that blastoids express the same genes in vitro that a regular embryo would at that stage in vivo, a strong demonstration of the power of blastoids as models for human embryonic development. Further highlighting the power of the lab's in vitro attached blastoid system, the team then used it to demonstrate that pathways that regulate the rise of the primitive streak and mesoderm in vivo also regulate blastoids symmetry breaking in vitro -- all with nothing but stem-cell-derived blastoid models.

Along the way, the team also demonstrated that gastrulation in vitro can begin at day 12, earlier than once thought. "This will change textbooks," Brivanlou says. "We've contributed to redefining the molecular signature and timing of the onset of gastrulation upon in vitro attachment."

Therapeutic possibilities

The results demonstrate that blastoids, when combined with the Brivanlou lab's unique attachment platform, are now capable of conveying insights into early human development that have long been inaccessible. De Santis envisions a future in which blastoid-based research leads to advancements in diagnosing and treating developmental disorders, or offers insights into potential causes of early miscarriages during gastrulation.

"Many couples can't have babies because the embryo doesn't attach properly, and many miscarriages occur in the first few weeks of pregnancy," De Santis explains. "We now have a model system that can help us understand the molecular mechanism that defines whether a pregnancy will be successful or not." In the near future, De Santis hopes to combine this method with machine learning to help predict pregnancy outcomes and the trajectories of developmental disorders by observing how model blastoids built with particular genetic makeups fare in vitro.

Read more at Science Daily

Toba supereruption unveils new insights into early human migration

Modern humans dispersed from Africa multiple times, but the event that led to global expansion occurred less than 100,000 years ago. Some researchers hypothesize that dispersals were restricted to "green corridors" formed during humid intervals when food was abundant and human populations expanded in lockstep with their environments. But a new study in Nature, including ASU researchers Curtis Marean, Christopher Campisano, and Jayde Hirniak, suggests that humans also may have dispersed during arid intervals along "blue highways" created by seasonal rivers. Researchers also found evidence of cooking and stone tools that represent the oldest evidence of archery.

Working in the Horn of Africa, researchers have uncovered evidence showing how early modern humans survived in the wake of the eruption of Toba, one of the largest supervolcanoes in history, some 74,000 years ago. The behavioral flexibility of these people not only helped them live through the supereruption but may have facilitated the later dispersal of modern humans out of Africa and across the rest of the world.

"This study confirms the results from Pinnacle Point in South Africa -- the eruption of Toba may have changed the environment in Africa, but people adapted and survived that eruption-caused environmental change," said Marean, research scientist with the Institute of Human Origins and Foundation Professor with the School of Human Evolution and Social Change.

The team investigated the Shinfa-Metema 1 site in the lowlands of present-day northwestern Ethiopia along the Shinfa River, a tributary of the Blue Nile River.

The supereruption occurred during the middle of the time when the site was occupied and is documented by tiny glass shards whose chemistry matches that of Toba.

Pinpoint timing through cryptotephra

"One of the ground-breaking implications of this study," said Marean, "is that with the new cryptotephra methods developed for our prior study in South Africa, and now applied here to Ethiopia, we can correlate sites across Africa, and perhaps the world, at a resolution of several weeks of time."

Cryptotephra are signature volcanic glass shards that can range from 80-20 microns in size, which is smaller than the diameter of a human hair. To extract these microscopic shards from archaeological sediment requires patience and great attention to detail.

"Searching for cryptotephra at these archaeological sites is like looking for a needle in a haystack, but not knowing if there is even a needle. However, having the ability to correlate sites 5,000 miles apart, and potentially further, to within weeks instead of thousands of years makes it all worth it," said Christopher Campisano, research scientist with the Institute of Human Origins and professor with the School of Human Evolution and Social Change.

"This study, once again," said Campisano, "highlights the importance of the University of Nevada-Las Vegas/Arizona State University team pushing the limits for successfully analyzing extremely low abundance cryptotephra to date and correlate archaeological sites across Africa."

The methods for identifying low abundance cryptotephra at Pinnacle Point were first developed at University of Nevada Las Vegas led by the late Gene Smith and Racheal Johnsen and now carried on at Arizona State University's Sediment and TEphra Preparation (STEP) Lab.

School of Human Evolution and Social Change graduate student Jayde Hirniak led ASU's effort to create its own cryptotephra lab -- the STEP Lab -- working with Campisano and building on methods developed at UNLV. Hirniak also collaborated with cryptotephra labs in the United Kingdom that work with sediment samples preserving hundreds or thousands of glass shards. Now Hirniak's primary expertise is in tephrochronology, which involves the use of volcanic ash to link archaeological and paleoenvironmental records and place them on the same timeline, which was her contribution to this research.

"Our lab at ASU was built to process extremely low abundance cryptotephra horizons (<10 shards per gram) using a highly specialized technique. There are only a few labs in the world with these capabilities," said Hirniak.

Migrations along "blue highways"

Based on isotope geochemistry of the teeth of fossil mammals and ostrich eggshells, they concluded that the site was occupied by humans during a time with long dry seasons on a par with some of the most seasonally arid habitats in East Africa today. Additional findings suggest that when river flows stopped during dry periods, people adapted by hunting animals that came to the remaining waterholes to drink. As waterholes continued to shrink, it became easier to capture fish without any special equipment, and diets shifted more heavily to fish.

Its climatic effects appear to have produced a longer dry season, causing people in the area to rely even more on fish. The shrinking of the waterholes may also have pushed humans to migrate outward in search of more food.

"As people depleted food in and around a given dry season waterhole, they were likely forced to move to new waterholes," said John Kappelman, a UT anthropology and earth and planetary sciences professor and lead author of the study. "Seasonal rivers thus functioned as 'pumps' that siphoned populations out along the channels from one waterhole to another, potentially driving the most recent out-of-Africa dispersal.

The humans who lived at Shinfa-Metema 1 are unlikely to have been members of the group that left Africa. However, the behavioral flexibility that helped them adapt to challenging climatic conditions such as the Toba supereruption was probably a key trait of Middle Stone Age humans that allowed our species to ultimately disperse from Africa and expand across the globe.

The people living in the Shinfa-Metema 1 site hunted a variety of terrestrial animals, from antelope to monkey, as attested to by cut marks on the bones, and apparently cooked their meals as shown by evidence of controlled fire at the site. The most distinctive stone tools are small, symmetrical triangular points. Analyses show that the points are most likely arrowheads that, at 74,000 years in age, represent the oldest evidence of archery.

Read more at Science Daily

Human shoulders and elbows first evolved as brakes for climbing apes

The rotating shoulders and extending elbows that allow humans to reach for a high shelf or toss a ball with friends may have first evolved as a natural braking system for our primate ancestors who simply needed to get out of trees without dying.

Dartmouth researchers report in the journal Royal Society Open Science that apes and early humans likely evolved free-moving shoulders and flexible elbows to slow their descent from trees as gravity pulled on their heavier bodies. When early humans left forests for the grassy savanna, the researchers say, their versatile appendages were essential for gathering food and deploying tools for hunting and defense.

The researchers used sports-analysis and statistical software to compare videos and still-frames they took of chimpanzees and small monkeys called mangabeys climbing in the wild. They found that chimps and mangabeys scaled trees similarly, with shoulders and elbows mostly bent close to the body. When climbing down, however, chimpanzees extended their arms above their heads to hold onto branches like a person going down a ladder as their greater weight pulled them downward rump-first.

Luke Fannin, first author of the study and a graduate student in Dartmouth's Ecology, Evolution, Environment and Society program, said the findings are among the first to identify the significance of "downclimbing" in the evolution of apes and early humans, which are more genetically related to each other than to monkeys. Existing research has observed chimps ascending and navigating trees -- usually in experimental setups -- but the researchers' extensive video from the wild allowed them to examine how the animals' bodies adapted to climbing down, Fannin said.

"Our study broaches the idea of downclimbing as an undervalued, yet incredibly important factor in the diverging anatomical differences between monkeys and apes that would eventually manifest in humans," Fannin said. "Downclimbing represented such a significant physical challenge given the size of apes and early humans that their morphology would have responded through natural selection because of the risk of falls."

"Our field has thought about apes climbing up trees for a long time -- what was essentially absent from the literature was any focus on them getting out of a tree. We've been ignoring the second half of this behavior," said study co-author Jeremy DeSilva, professor and chair of anthropology at Dartmouth.

"The first apes evolved 20 million years ago in the kind of dispersed forests where they would go up a tree to get their food, then come back down to move on to the next tree," DeSilva said.

"Getting out of a tree presents all kinds of new challenges. Big apes can't afford to fall because it could kill or badly injure them. Natural selection would have favored those anatomies that allowed them to descend safely."

Flexible shoulders and elbows passed on from ancestral apes would have allowed early humans such as Australopithecus to climb trees at night for safety and come down in the daylight unscathed, DeSilva said. Once Homo erectus could use fire to protect itself from nocturnal predators, the human form took on broader shoulders capable of a 90-degree angle that -- combined with free-moving shoulders and elbows -- made our ancestors excellent shots with a spear (apes cannot throw accurately).

"It's that same early-ape anatomy with a couple of tweaks. Now you have something that can throw a spear or rocks to protect itself from being eaten or to kill things to eat for itself. That's what evolution does -- it's a great tinkerer," DeSilva said.

"Climbing down out of a tree set the anatomical stage for something that evolved millions of years later," he said. "When an NFL quarterback throws a football, that movement is all thanks to our ape ancestors."

Despite chimps' lack of grace, Fannin said, their arms have adapted to ensure the animals reach the ground safely -- and their limbs are remarkably similar to those of modern humans.

"It's the template that we came from -- going down was probably far more of a challenge for our early ancestors, too," Fannin said. "Even once humans became upright, the ability to ascend, then descend, a tree would've been incredibly useful for safety and nourishment, which is the name of the game when it comes to survival.We're modified, but the hallmarks of our ape ancestry remain in our modern skeletons."

The researchers also studied the anatomical structure of chimp and mangabey arms using skeletal collections at Harvard University and The Ohio State University, respectively. Like people, chimps have a shallow ball-and-socket shoulder that -- while more easily dislocated -- allows for a greater range of movement, Fannin said. And like humans, chimps can fully extend their arms thanks to the reduced length of the bone just behind the elbow known as the olecranon process.

Mangabeys and other monkeys are built more like quadrupedal animals such as cats and dogs, with deep pear-shaped shoulder sockets and elbows with a protruding olecranon process that make the joint resemble the letter L. While these joints are more stable, they have a much more limited flexibility and range of movement.

The researchers' analysis showed that the angle of a chimp's shoulders was 14 degrees greater during descent than when climbing up. And their arm extended outward at the elbow 34 degrees more when coming down from a tree than going up. The angles at which mangabeys positioned their shoulders and elbows were only marginally different -- 4 degrees or less -- when they were ascending a tree versus downclimbing.

"If cats could talk, they would tell you that climbing down is trickier than climbing up and many human rock climbers would agree. But the question is why is it so hard," said study co-author Nathaniel Dominy, the Charles Hansen Professor of Anthropology and Fannin's adviser.

"The reason is that you're not only resisting the pull of gravity, but you also have to decelerate," Dominy said. "Our study is important for tackling a theoretical problem with formal measurements of how wild primates climb up and down. We found important differences between monkeys and chimpanzees that may explain why the shoulders and elbows of apes evolved greater flexibility."

Co-author Mary Joy, who led the study with Fannin for her undergraduate thesis and graduated from Dartmouth in 2021, was reviewing videos of chimps that DeSilva had filmed when she noticed the difference in how the animals descended trees than how they went up them.

"It was very erratic, just crashing down, everything's flying. It's very much a controlled fall," Joy said. "In the end, we concluded that the way chimps descend a tree is likely related to weight. Greater momentum potentially expends less energy and they're much more likely to reach the ground safely than by making small, restricted movements."

But as a trail runner, Joy knew the pained feeling of inching down an incline in short clips instead of just hurtling down the path with the pull of gravity, her legs extended forward to catch her at the end of each stride.

"When I'm moving downhill, the slower I'm going and restricting my movement, the more I'm fatiguing. It catches up to me very quickly. No one would think the speed and abandon with which chimps climb down from trees would be the preferred method for a heavier primate, but my experience tells me it's more energy efficient," she said.

Read more at Science Daily

How a massive North Atlantic cooling event disrupted early human occupation in Europe

A new study published in the journal Science finds that around 1.12 million years ago a massive cooling event in the North Atlantic and corresponding shifts in climate, vegetation and food resources disrupted early human occupation of Europe.

The study published by an international group of scientists from the UK, South Korea and Spain presents observational and modelling evidence documenting that unprecedented climate stress changed the course of early human history.

Archaic humans, known as Homo erectus moved from Africa into central Eurasia around 1.8 million years. From there on they spread towards western Europe, reaching the Iberian peninsula around 1.5 million years ago (Ma). Experiencing initially rather mild climatic conditions, these groups eventually established a foothold in southern Europe, as documented by several dated fossils and stone tools from this period. But given the increasing intensity of glacial cycles in Europe from 1.2 Ma onwards, it remains unknown for how long early humans lived in this area and whether the occupation was interrupted by worsening climate conditions.

To better understand the environmental conditions, which early human species in Europe experienced, the team of pollen experts, oceanographers, climate modelers, archeologists, and anthropologists combined data of a deep ocean sediment cores from the eastern subtropical Atlantic with new supercomputer climate model and human habitat model simulations covering the period of the depopulation event.

Sieving through thousands of small plant pollen stored in the ocean sediment core and analyzing preserved temperature-sensitive organic compounds left by tiny algae, which lived over a million years ago, the scientists discovered that around 1.127 million years ago, the climate over the eastern North Atlantic and the adjacent land suddenly cooled by 7oC.

"This massive cooling marks one of the first terminal stadial events in the paleoclimatic record. It occurred during the last phase of a glacial cycle, when ice-sheets disintegrated, releasing large amounts of freshwater into the ocean, and causing ocean circulation changes and a southward expansion of sea ice," says Prof. Chronis Tzedakis from University College London (UCL), senior author of the study.

The pollen data extracted from the ocean sediment core further add to this scenario "Rivers and winds bring tiny pollen from the adjacent land to the ocean, where they sink and get deposited in the deep ocean. According to our ocean sediment core pollen analysis, the North Atlantic cooling event switched western European vegetation to an inhospitable semi-desert landscape.," adds Dr. Vasiliki Margari from UCL, lead author of the study.

To quantify how early humans may have reacted to such an unprecedented climate anomaly, scientists from the IBS Center for Climate Physics (ICCP) in South Korea, conducted new computer model simulations for this period. By adding glacial freshwater to the North Atlantic, Dr. Kyung-Sook Yun, and Ms. Hyuna Kim from the ICCP were able to reproduce key features of the terminal stadial event, such as the cooling and drying over southern Europe. "We then used this global climate model simulation as an input for a human habitat model, which determines whether certain environmental conditions were suitable for early Homo erectus or not. We found that over many areas of southern Europe, early human species such as Homo erectus would have not been able to survive" describes Prof. Axel Timmermann, Director of the ICCP at Pusan National University and co-corresponding author of the study.

Even though the cooling event only lasted for about 4,000 years, a lack of stone tools and human remains over the next 200,000 years further raises the possibility of a long-lasting hiatus in European occupation. Europe was again repopulated around 900 thousand years ago by a group that is often referred to as Homo antecessor. This group and its descendants were much more resilient, because they were able to adapt to the increasing intensity of glacial conditions over Europe.

Read more at Science Daily

Early humans were weapon woodwork experts, study finds

A 300,000-year-old hunting weapon has shone a new light on early humans as woodworking masters, according to a new study.

State-of-the-art analysis of a double-pointed wooden throwing stick, found in Schöningen in Germany three decades ago, shows it was scraped, seasoned and sanded before being used to kill animals. The research indicates early humans' woodworking techniques were more developed and sophisticated than previously understood.

The findings, published today (Wednesday, 19 July) in PLOS ONE, also suggest the creation of lightweight weapons may have enabled group hunts of medium and small animals. The use of throwing sticks as hunting aids could have involved the entire community, including children.

Dr Annemieke Milks, of the University of Reading's Department of Archaeology, led the research. She said: "Discoveries of wooden tools have revolutionised our understanding of early human behaviours. Amazingly these early humans demonstrated an ability to plan well in advance, a strong knowledge of the properties of wood, and many sophisticated woodworking skills that we still use today.

"These lightweight throwing sticks may have been easier to launch than heavier spears, indicating the potential for the whole community to take part. Such tools could have been used by children while learning to throw and hunt."

Co-author Dirk Leder said: "The Schöningen humans used a spruce branch to make this aerodynamic and ergonomic tool. The woodworking involved multiple steps including cutting and stripping off the bark, carving it into an aerodynamic shape, scraping away more of the surface, seasoning the wood to avoid cracking and warping, and sanding it for easier handling."

High-impact weapon

Found in 1994, the 77cm-long stick is one of several different tools discovered in Schöningen, which includes throwing spears, thrusting spears and a second similarly sized throwing stick.

The double-pointed throwing stick -- analysed to an exceptionally high level of detail for this new study -- was most likely used by early humans to hunt medium-sized game like red and roe deer, and possibly fast-small prey including hare and birds that were otherwise difficult to catch. The throwing sticks would have been thrown rotationally -- similar to a boomerang -- rather than overhead like a modern-day javelin and may have enabled early humans to throw as far as 30 metres. Although lightweight, the high velocities at which such weapons can be launched could have resulted in deadly high-energy impacts.

The fine surface, carefully shaped points and polish from handling suggest this was a piece of personal kit with repeated use, rather than a quickly made tool that was carelessly discarded.

Principal investigator Thomas Terberger said: "The systematic analysis of the wooden finds of the Schöningen site financed by German Research Foundation provides valuable new insights and further exciting information on these early wooden weapons can be expected soon."

Read more at Science Daily

Archaeologists uncover oldest known projectile points in the Americas

Oregon State University archaeologists have uncovered projectile points in Idaho that are thousands of years older than any previously found in the Americas, helping to fill in the history of how early humans crafted and used stone weapons.

The 13 full and fragmentary projectile points, razor sharp and ranging from about half an inch to 2 inches long, are from roughly 15,700 years ago, according to carbon-14 dating. That's about 3,000 years older than the Clovis fluted points found throughout North America, and 2,300 years older than the points previously found at the same Cooper's Ferry site along the Salmon River in present-day Idaho.

The findings were published today in the journal Science Advances.

"From a scientific point of view, these discoveries add very important details about what the archaeological record of the earliest peoples of the Americas looks like," said Loren Davis, an anthropology professor at OSU and head of the group that found the points. "It's one thing to say, 'We think that people were here in the Americas 16,000 years ago;' it's another thing to measure it by finding well-made artifacts they left behind."

Previously, Davis and other researchers working the Cooper's Ferry site had found simple flakes and pieces of bone that indicated human presence about 16,000 years ago. But the discovery of projectile points reveals new insights into the way the first Americans expressed complex thoughts through technology at that time, Davis said.

The Salmon River site where the points were found is on traditional Nez Perce land, known to the tribe as the ancient village of Nipéhe. The land is currently held in public ownership by the federal Bureau of Land Management.

The points are revelatory not just in their age, but in their similarity to projectile points found in Hokkaido, Japan, dating to 16,000-20,000 years ago, Davis said. Their presence in Idaho adds more detail to the hypothesis that there are early genetic and cultural connections between the ice age peoples of Northeast Asia and North America.

"The earliest peoples of North America possessed cultural knowledge that they used to survive and thrive over time. Some of this knowledge can be seen in the way people made stone tools, such as the projectile points found at the Cooper's Ferry site," Davis said. "By comparing these points with other sites of the same age and older, we can infer the spatial extents of social networks where this technological knowledge was shared between peoples."

These slender projectile points are characterized by two distinct ends, one sharpened and one stemmed, as well as a symmetrical beveled shape if looked at head-on. They were likely attached to darts, rather than arrows or spears, and despite the small size, they were deadly weapons, Davis said.

"There's an assumption that early projectile points had to be big to kill large game; however, smaller projectile points mounted on darts will penetrate deeply and cause tremendous internal damage," he said. "You can hunt any animal we know about with weapons like these."

These discoveries add to the emerging picture of early human life in the Pacific Northwest, Davis said. "Finding a site where people made pits and stored complete and broken projectile points nearly 16,000 years ago gives us valuable details about the lives of our region's earliest inhabitants."

The newly discovered pits are part of the larger Cooper's Ferry record, where Davis and colleagues have previously reported a 14,200-year-old fire pit and a food-processing area containing the remains of an extinct horse. All told, they found and mapped more than 65,000 items, recording their locations to the millimeter for precise documentation.

The projectile points were uncovered over multiple summers between 2012 and 2017, with work supported by a funding partnership held between OSU and the BLM. All excavation work has been completed and the site is now covered. The BLM installed interpretive panels and a kiosk at the site to describe the work.

Read more at Science Daily

Early humans may have first walked upright in the trees

Human bipedalism -- walking upright on two legs -- may have evolved in trees, and not on the ground as previously thought, according to a new study involving UCL researchers.

In the study, published today in the journal Science Advances, researchers from UCL, the University of Kent, and Duke University, USA, explored the behaviours of wild chimpanzees -- our closest living relative -- living in the Issa Valley of western Tanzania, within the region of the East African Rift Valley. Known as 'savanna-mosaic' -- a mix of dry open land with few trees and patches of dense forest -- the chimpanzees' habitat is very similar to that of our earliest human ancestors and was chosen to enable the scientists to explore whether the openness of this type of landscape could have encouraged bipedalism in hominins.

The study is the first of its kind to explore if savanna-mosaic habitats would account for increased time spent on the ground by the Issa chimpanzees, and compares their behaviour to other studies on their solely forest-dwelling cousins in other parts of Africa.

Overall, the study found that the Issa chimpanzees spent as much time in the trees as other chimpanzees living in dense forests, despite their more open habitat, and were not more terrestrial (land-based) as expected.

Furthermore, although the researchers expected the Issa chimpanzees to walk upright more in open savanna vegetation, where they cannot easily travel via the tree canopy, more than 85% of occurrences of bipedalism took place in the trees.

The authors say that their findings contradict widely accepted theories that suggest that it was an open, dry savanna environment that encouraged our prehistoric human relatives to walk upright -- and instead suggests that they may have evolved to walk on two feet to move around the trees.

Study co-author Dr Alex Piel (UCL Anthropology) said: "We naturally assumed that because Issa has fewer trees than typical tropical forests, where most chimpanzees live, we would see individuals more often on the ground than in the trees. Moreover, because so many of the traditional drivers of bipedalism (such as carrying objects or seeing over tall grass, for example) are associated with being on the ground, we thought we'd naturally see more bipedalism here as well. However, this is not what we found.

"Our study suggests that the retreat of forests in the late Miocene-Pliocene era around five million years ago and the more open savanna habitats were in fact not a catalyst for the evolution of bipedalism. Instead, trees probably remained essential to its evolution -- with the search for food-producing trees a likely a driver of this trait."

To establish their findings, the researchers recorded more than 13,700 instantaneous observations of positional behaviour from 13 chimpanzee adults (six females and seven males), including almost 2,850 observations of individual locomotor events (e.g., climbing, walking, hanging, etc.), over the course of the 15-month study. They then used the relationship between tree/land-based behaviour and vegetation (forest vs woodland) to investigate patterns of association. Similarly, they noted each instance of bipedalism and whether it was associated with being on the ground or in the trees.

The authors note that walking on two feet is a defining feature of humans when compared to other great apes, who "knuckle walk." Yet, despite their study, researchers say why humans alone amongst the apes first began to walk on two feet still remains a mystery.

Study co-author Dr Fiona Stewart (UCL Anthropology) said: "To date, the numerous hypotheses for the evolution of bipedalism share the idea that hominins (human ancestors) came down from the trees and walked upright on the ground, especially in more arid, open habitats that lacked tree cover. Our data do not support that at all.

Read more at Science Daily

Jawbone may represent earliest presence of humans in Europe

For over a century, one of the earliest human fossils ever discovered in Spain has been long considered a Neanderthal. However, new analysis from an international research team, including scientists at Binghamton University, State University of New York, dismantles this century-long interpretation, demonstrating that this fossil is not a Neanderthal; rather, it may actually represent the earliest presence of Homo sapiens ever documented in Europe.

In 1887, a fossil mandible was discovered during quarrying activities in the town of Banyoles, Spain, and has been studied by different researchers over the past century. The Banyoles fossil likely dates to between approximately 45,000-65,000 years ago, at a time when Europe was occupied by Neanderthals, and most researchers have generally linked it to this species.

"The mandible has been studied throughout the past century and was long considered to be a Neanderthal based on its age and location, and the fact that it lacks one of the diagnostic features of Homo sapiens: a chin," said Binghamton University graduate student Brian Keeling.

The new study relied on virtual techniques, including CT scanning of the original fossil. This was used to virtually reconstruct missing parts of the fossil, and then to generate a 3D model to be analyzed on the computer.

The authors studied the expressions of distinct features on the mandible from Banyoles that are different between our own species, Homo sapiens, and the Neanderthals, our closest evolutionary cousins.

The authors applied a methodology known as "three-dimensional geometric morphometrics" that analyzes the geometric properties of the bone's shape. This makes it possible to directly compare the overall shape of Banyoles to Neanderthals and H. sapiens.

"Our results found something quite surprising -- Banyoles shared no distinct Neanderthal traits and did not overlap with Neanderthals in its overall shape," said Keeling.

While Banyoles seemed to fit better with Homo sapiens in both the expression of its individual features and its overall shape, many of these features are also shared with earlier human species, complicating an immediate assignment to Homo sapiens. In addition, Banyoles lacks a chin, one of the most characteristic features of Homo sapiens mandibles.

"We were confronted with results that were telling us Banyoles is not a Neanderthal, but the fact that it does not have a chin made us think twice about assigning it to Homo sapiens," said Rolf Quam, professor of anthropology at Binghamton University, State University of New York. "The presence of a chin has long been considered a hallmark of our own species."

Given this, reaching a scientific consensus on what species Banyoles represents is a challenge. The authors also compared Banyoles with an early Homo sapiens mandible from a site called Peştera cu Oase in Romania. Unlike Banyoles, this mandible shows a full chin along with some Neanderthal features, and an ancient DNA analysis has revealed this individual had a Neanderthal ancestor four to six generations ago. Since the Banyoles mandible shared no distinct features with Neanderthals, the researchers ruled out the possibility of mixture between Neanderthals and H. sapiens to explain its anatomy.

The authors point out that some of the earliest Homo sapiens fossils from Africa, predating Banyoles by more than 100,000 years, do show less pronounced chins than in living populations.

Thus, these scientists developed two possibilities for what the Banyoles mandible may represent: a member of a previously unknown population of Homo sapiens that coexisted with the Neanderthals; or a hybrid between a member of this Homo sapiens group and a non-Neanderthal unidentified human species. However, at the time of Banyoles, the only fossils recovered from Europe are Neanderthals, making this latter hypothesis less likely.

"If Banyoles is really a member of our species, this prehistoric human would represent the earliest H. sapiens ever documented in Europe," said Keeling.

Whichever species this mandible belongs to, Banyoles is clearly not a Neanderthal at a time when Neanderthals were believed to be the sole occupants of Europe.

The authors conclude that "the present situation makes Banyoles a prime candidate for ancient DNA or proteomic analyses, which may shed additional light on its taxonomic affinities."

Read more at Science Daily

Fossils in the 'Cradle of Humankind' may be more than a million years older than previously thought

The earth doesn't give up its secrets easily -- not even in the "Cradle of Humankind" in South Africa, where a wealth of fossils relating to human evolution have been found.

For decades, scientists have studied these fossils of early human ancestors and their long-lost relatives. Now, a dating method developed by a Purdue University geologist just pushed the age of some of these fossils found at the site of Sterkfontein Caves back more than a million years. This would make them older than Dinkinesh, also called Lucy, the world's most famous Australopithecus fossil.

The "Cradle of Humankind" is a UNESCO World Heritage Site in South Africa that comprises a variety of fossil-bearing cave deposits, including at Sterkfontein Caves. Sterkfontein was made famous by the discovery of the first adult Australopithecus, an ancient hominin, in 1936. Hominins includes humans and our ancestral relatives, but not the other great apes. Since then, hundreds of Australopithecus fossils have been found there, including the well-known Mrs. Ples, and the nearly complete skeleton known as Little Foot. Paleoanthropologists and other scientists have studied Sterkfontein and other cave sites in the Cradle of Humankind for decades to shed light on human and environmental evolution over the past 4 million years.

Darryl Granger, a professor of earth, atmospheric, and planetary sciences in Purdue University's College of Science, is one of those scientists, working as part of an international team. Granger specializes in dating geologic deposits, including those in caves. As a doctoral student, he devised a method for dating buried cave sediments that is now used by researchers all over the world. His previous work at Sterkfontein dated the Little Foot skeleton to about 3.7 million years old, but scientists are still debating the age of other fossils at the site.

In a study published in the Proceedings of the National Academy of Sciences, Granger and a team of scientists including researchers from the University of the Witwatersrand in Johannesburg, South Africa and the University Toulouse Jean Jaurès in France, have discovered that not only Little Foot, but all of the Australopithecus-bearing cave sediments date from about 3.4 to 3.7 million years old, rather than 2-2.5 million years old as scientists previously theorized. That age places these fossils toward the beginning of the Australopithecus era, rather than near the end. Dinkinesh, who hails from Ethiopia, is 3.2 million years old, and her species, Australopithecus africanus, hails back to about 3.9 million years old.

Sterkfontein is a deep and complex cave system that preserves a long history of hominin occupation of the area. Understanding the dates of the fossils here can be tricky, as rocks and bones tumbled to the bottom of a deep hole in the ground, and there are few ways to date cave sediments.

In East Africa, where many hominin fossils have been found, the Great Rift Valley volcanoes lay down layers of ash that can be dated. Researchers use those layers to estimate how old a fossil is. In South Africa -- especially in a cave -- the scientists don't have that luxury. They typically use other animal fossils found around the bones to estimate their age or calcite flowstone deposited in the cave. But bones can shift in the cave, and young flowstone can be deposited in old sediment, making those methods potentially incorrect. A more accurate method is to date the actual rocks in which the fossils were found. The concrete-like matrix that embeds the fossil, called breccia, is the material Granger and his team analyze.

"Sterkfontein has more Australopithecus fossils than anywhere else in the world," Granger said. "But it's hard to get a good date on them. People have looked at the animal fossils found near them and compared the ages of cave features like flowstones and gotten a range of different dates. What our data does is resolve these controversies. It shows that these fossils are old -- much older than we originally thought."

Granger and the team used accelerator mass spectrometry to measure radioactive nuclides in the rocks, as well as geologic mapping and an intimate understanding of how cave sediments accumulate to determine the age of the Australopithecus-bearing sediments at Sterkfontein,

Granger and the research group at the Purdue Rare Isotope Measurement Laboratory (PRIME Lab) study so-called cosmogenic nuclides and what they can reveal about the history of fossils, geological features and rock. Cosmogenic nuclides are extremely rare isotopes produced by cosmic rays -- high-energy particles that constantly bombard the earth. These incoming cosmic rays have enough energy to cause nuclear reactions inside rocks at the ground surface, creating new, radioactive isotopes within the mineral crystals. An example is aluminum-26: aluminum that is missing a neutron and slowly decays to turn into magnesium over a period of millions of years. Since aluminum-26 is formed when a rock is exposed at the surface, but not after it has been deeply buried in a cave, PRIME lab researchers can date cave sediments (and the fossils within them) by measuring levels of aluminum-26 in tandem with another cosmogenic nuclide, beryllium-10.

In addition to the new dates at Sterkfontein based on cosmogenic nuclides, the research team made careful maps of the cave deposits and showed how animal fossils of different ages would have been mixed together during excavations in the 1930s and 1940s, leading to decades of confusion with the previous ages. "What I hope is that this convinces people that this dating method gives reliable results," Granger said. "Using this method, we can more accurately place ancient humans and their relatives in the correct time periods, in Africa, and elsewhere across the world."

Read more at Science Daily

Prehistoric people created art by firelight, new research reveals

Our early ancestors probably created intricate artwork by firelight, an examination of 50 engraved stones unearthed in France has revealed.

The stones were incised with artistic designs around 15,000 years ago and have patterns of heat damage which suggests they were carved close to the flickering light of a fire, the new study has found.

The study, by researchers at the Universities of York and Durham, looked at the collection of engraved stones, known as plaquettes, which are now held in the British Museum. They are likely to have been made using stone tools by Magdalenian people, an early hunter-gatherer culture dating from between 23,000 and 14,000 years ago.

The researchers identified patterns of pink heat damage around the edges of some of the stones, providing evidence that they had been placed in close proximity to a fire.

Following their discovery, the researchers have experimented with replicating the stones themselves and used 3D models and virtual reality software to recreate the plaquettes as prehistoric artists would have seen them: under fireside light conditions and with the fresh white lines engravers would have made as they first cut into the rock thousands of years ago.

Lead author of the study, Dr Andy Needham from the Department of Archaeology at the University of York and Co-Director of the York Experimental Archaeology Research Centre said: "It has previously been assumed that the heat damage visible on some plaquettes was likely to have been caused by accident, but experiments with replica plaquettes showed the damage was more consistent with being purposefully positioned close to a fire.

"In the modern day, we might think of art as being created on a blank canvas in daylight or with a fixed light source; but we now know that people 15,000 years ago were creating art around a fire at night, with flickering shapes and shadows."

Working under these conditions would have had a dramatic effect on the way prehistoric people experienced the creation of art, the researchers say. It may have activated an evolutionary capacity designed to protect us from predators called "Pareidolia," where perception imposes a meaningful interpretation such as the form of an animal, a face or a pattern where there is none.

Dr Needham added: "Creating art by firelight would have been a very visceral experience, activating different parts of the human brain. We know that flickering shadows and light enhance our evolutionary capacity to see forms and faces in inanimate objects and this might help explain why it's common to see plaquette designs that have used or integrated natural features in the rock to draw animals or artistic forms."

The Magdalenian era saw a flourishing of early art, from cave art and the decoration of tools and weapons to the engraving of stones and bones.

Co-author of the study, PhD student Izzy Wisher from the Department of Archaeology at the University of Durham, said: "During the Magdalenian period conditions were very cold and the landscape was more exposed. While people were well-adapted to the cold, wearing warm clothing made from animal hides and fur, fire was still really important for keeping warm. Our findings reinforce the theory that the warm glow of the fire would have made it the hub of the community for social gatherings, telling stories and making art.

Read more at Science Daily

Early human habitats linked to past climate shifts

A study published in Nature by an international team of scientists provides clear evidence for a link between astronomically-driven climate change and human evolution.

By combining the most extensive database of well-dated fossil remains and archeological artefacts with an unprecedented new supercomputer model simulating earth's climate history of the past 2 million years, the team of experts in climate modeling, anthropology and ecology was able to determine under which environmental conditions archaic humans likely lived.

The impact of climate change on human evolution has long been suspected, but has been difficult to demonstrate due to the paucity of climate records near human fossil-bearing sites. To bypass this problem, the team instead investigated what the climate in their computer simulation was like at the times and places humans lived, according to the archeological record. This revealed the preferred environmental conditions of different groups of hominins[1]. From there, the team looked for all the places and times those conditions occurred in the model, creating time-evolving maps of potential hominin habitats.

"Even though different groups of archaic humans preferred different climatic environments, their habitats all responded to climate shifts caused by astronomical changes in earth's axis wobble, tilt, and orbital eccentricity with timescales ranging from 21 to 400 thousand years," said Axel Timmermann, lead author of the study and Director of the IBS Center for Climate Physics (ICCP) at Pusan National University in South Korea.

To test the robustness of the link between climate and human habitats, the scientists repeated their analysis, but with ages of the fossils shuffled like a deck of cards. If the past evolution of climatic variables did not impact where and when humans lived, then both methods would result in the same habitats. However, the researchers found significant differences in the habitat patterns for the three most recent hominin groups (Homo sapiens, Homo neanderthalensis and Homo heidelbergensis) when using the shuffled and the realistic fossil ages. "This result implies that at least during the past 500 thousand years the real sequence of past climate change, including glacial cycles, played a central role in determining where different hominin groups lived and where their remains have been found," said Prof. Timmermann.

"The next question we set out to address was whether the habitats of the different human species overlapped in space and time. Past contact zones provide crucial information on potential species successions and admixture," said Prof. Pasquale Raia from the Università di Napoli Federico II, Naples, Italy, who together with his research team compiled the dataset of human fossils and archeological artefacts used in this study. From the contact zone analysis, the researchers then derived a hominin family tree, according to which Neanderthals and likely Denisovans derived from the Eurasian clade of Homo heidelbergensis around 500-400 thousand years ago, whereas Homo sapiens' roots can be traced back to Southern African populations of late Homo heidelbergensis around 300 thousand years ago.

"Our climate-based reconstruction of hominin lineages is quite similar to recent estimates obtained from either genetic data or the analysis of morphological differences in human fossils, which increases our confidence in the results," remarks Dr. Jiaoyang Ruan, co-author of the study and postdoctoral research fellow at the IBS Center for Climate Physics.

The new study was made possible by using one of South Korea's fastest supercomputers named Aleph. Located at the headquarters of the Institute for Basic Science in Daejeon, Aleph ran non-stop for over 6 months to complete the longest comprehensive climate model simulation to date. "The model generated 500 Terabytes of data, enough to fill up several hundred hard disks," said Dr. Kyung-Sook Yun, a researcher at the IBS Center for Climate Physics who conducted the experiments. "It is the first continuous simulation with a state-of-the-art climate model that covers earth's environmental history of the last 2 million years, representing climate responses to the waxing and waning of ice-sheets, changes in past greenhouse gas concentrations, as well as the marked transition in the frequency of glacial cycles around 1 million years ago," adds Dr. Yun.

"So far, the paleoanthropological community has not utilized the full potential of such continuous paleoclimate model simulations. Our study clearly illustrates the value of well-validated climate models to address fundamental questions on our human origins," says Prof. Christoph Zollikofer from the University of Zurich, Switzerland and co-author of the study.

Going beyond the question of early human habitats, and times and places of human species' origins, the research team further addressed how humans may have adapted to varying food resources over the past 2 million years. "When we looked at the data for the five major hominin groups, we discovered an interesting pattern. Early African hominins around 2-1 million years ago preferred stable climatic conditions. This constrained them to relatively narrow habitable corridors. Following a major climatic transition about 800 thousand year ago, a group known under the umbrella term Homo heidelbergensis adapted to a much wider range of available food resources, which enabled them to become global wanderers, reaching remote regions in Europe and eastern Asia," said Elke Zeller, PhD student at Pusan National University and co-author of the study.

Read more at Science Daily

Early humans placed the hearth at the optimal location in their cave -- for maximum benefit and minimum smoke exposure

A groundbreaking study in prehistoric archaeology at Tel Aviv University provides evidence for high cognitive abilities in early humans who lived 170,000 years ago. In a first-of-its kind study, the researchers developed a software-based smoke dispersal simulation model and applied it to a known prehistoric site. They discovered that the early humans who occupied the cave had placed their hearth at the optimal location -- enabling maximum utilization of the fire for their activities and needs while exposing them to a minimal amount of smoke.

The study was led by PhD student Yafit Kedar, and Prof. Ran Barkai from the Jacob M. Alkow Department of Archaeology and Ancient Near Eastern Cultures at TAU, together with Dr. Gil Kedar. The paper was published in Scientific Reports.

Yafit Kedar explains that the use of fire by early humans has been widely debated by researchers for many years, regarding questions such as: At what point in their evolution did humans learn how to control fire and ignite it at will? When did they begin to use it on a daily basis? Did they use the inner space of the cave efficiently in relation to the fire? While all researchers agree that modern humans were capable of all these things, the dispute continues about the skills and abilities of earlier types of humans.

Yafit Kedar: "One focal issue in the debate is the location of hearths in caves occupied by early humans for long periods of time. Multilayered hearths have been found in many caves, indicating that fires had been lit at the same spot over many years. In previous studies, using a software-based model of air circulation in caves, along with a simulator of smoke dispersal in a closed space, we found that the optimal location for minimal smoke exposure in the winter was at the back of the cave. The least favorable location was the cave's entrance."

In the current study the researchers applied their smoke dispersal model to an extensively studied prehistoric site -- the Lazaret Cave in southeastern France, inhabited by early humans around 170,000 to 150,000 years ago. Yafit Kedar: "According to our model, based on previous studies, placing the hearth at the back of the cave would have reduced smoke density to a minimum, allowing the smoke to circulate out of the cave right next to the ceiling. But in the archaeological layers we examined, the hearth was located at the center of the cave. We tried to understand why the occupants had chosen this spot, and whether smoke dispersal had been a significant consideration in the cave's spatial division into activity areas."

To answer these questions, the researchers performed a range of smoke dispersal simulations for 16 hypothetical hearth locations inside the 290sqm cave. For each hypothetical hearth they analyzed smoke density throughout the cave using thousands of simulated sensors placed 50cm apart from the floor to the height of 1.5m.

To understand the health implications of smoke exposure, measurements were compared with the average smoke exposure recommendations of the World Health Organization. In this way four activity zones were mapped in the cave for each hearth: a red zone which is essentially out of bounds due to high smoke density; a yellow area suitable for short-term occupation of several minutes; a green area suitable for long-term occupation of several hours or days; and a blue area which is essentially smoke-free.

Yafit and Gil Kedar: "We found that the average smoke density, based on measuring the number of particles per spatial unit, is in fact minimal when the hearth is located at the back of the cave -- just as our model had predicted. But we also discovered that in this situation, the area with low smoke density, most suitable for prolonged activity, is relatively distant from the hearth itself.

Early humans needed a balance -- a hearth close to which they could work, cook, eat, sleep, get together, warm themselves, etc. while exposed to a minimum amount of smoke. Ultimately, when all needs are taken into consideration -- daily activities vs. the damages of smoke exposure -- the occupants placed their hearth at the optimal spot in the cave."

The study identified a 25m2 area in the cave which would be optimal for locating the hearth in order to enjoy its benefits while avoiding too much exposure to smoke. Astonishingly, in the several layers examined by in this study, the early humans actually did place their hearth within this area.

Prof. Barkai concludes: "Our study shows that early humans were able, with no sensors or simulators, to choose the perfect location for their hearth and manage the cave's space as early as 170,000 years ago -- long before the advent of modern humans in Europe. This ability reflects ingenuity, experience, and planned action, as well as awareness of the health damage caused by smoke exposure. In addition, the simulation model we developed can assist archaeologists excavating new sites, enabling them to look for hearths and activity areas at their optimal locations."

Read more at Science Daily

Earliest human remains in eastern Africa dated to more than 230,000 years ago

The age of the oldest fossils in eastern Africa widely recognised as representing our species, Homo sapiens, has long been uncertain. Now, dating of a massive volcanic eruption in Ethiopia reveals they are much older than previously thought.

The remains -- known as Omo I -- were found in Ethiopia in the late 1960s, and scientists have been attempting to date them precisely ever since, by using the chemical fingerprints of volcanic ash layers found above and below the sediments in which the fossils were found.

An international team of scientists, led by the University of Cambridge, has reassessed the age of the Omo I remains -- and Homo sapiens as a species. Earlier attempts to date the fossils suggested they were less than 200,000 years old, but the new research shows they must be older than a colossal volcanic eruption that took place 230,000 years ago. The results are reported in the journal Nature.

The Omo I remains were found in the Omo Kibish Formation in southwestern Ethiopia, within the East African Rift valley. The region is an area of high volcanic activity, and a rich source of early human remains and artefacts such as stone tools. By dating the layers of volcanic ash above and below where archaeological and fossil materials are found, scientists identified Omo I as the earliest evidence of our species, Homo sapiens.

"Using these methods, the generally accepted age of the Omo fossils is under 200,000 years, but there's been a lot of uncertainty around this date," said Dr Céline Vidal from Cambridge's Department of Geography, the paper's lead author. "The fossils were found in a sequence, below a thick layer of volcanic ash that nobody had managed to date with radiometric techniques because the ash is too fine-grained."

As part of a four-year project led by Professor Clive Oppenheimer, Vidal and her colleagues have been attempting to date all the major volcanic eruptions in the Ethiopian Rift around the time of the emergence of Homo sapiens, a period known as the late Middle Pleistocene.

The researchers collected pumice rock samples from the volcanic deposits and ground them down to sub-millimetre size. "Each eruption has its own fingerprint -- its own evolutionary story below the surface, which is determined by the pathway the magma followed," said Vidal. "Once you've crushed the rock, you free the minerals within, and then you can date them, and identify the chemical signature of the volcanic glass that holds the minerals together."

The researchers carried out new geochemical analysis to link the fingerprint of the thick volcanic ash layer from the Kamoya Hominin Site (KHS ash) with an eruption of Shala volcano, more than 400 kilometres away. The team then dated pumice samples from the volcano to 230,000 years ago. Since the Omo I fossils were found deeper than this particular ash layer, they must be more than 230,000 years old.

"First I found there was a geochemical match, but we didn't have the age of the Shala eruption," said Vidal. "I immediately sent the samples of Shala volcano to our colleagues in Glasgow so they could measure the age of the rocks. When I received the results and found out that the oldest Homo sapiens from the region was older than previously assumed, I was really excited."

"The Omo Kibish Formation is an extensive sedimentary deposit which has been barely accessed and investigated in the past," said co-author and co-leader of the field investigation Professor Asfawossen Asrat from Addis Ababa University in Ethiopia, who is currently at BIUST in Botswana. "Our closer look into the stratigraphy of the Omo Kibish Formation, particularly the ash layers, allowed us to push the age of the oldest Homo sapiens in the region to at least 230,000 years."

"Unlike other Middle Pleistocene fossils which are thought to belong to the early stages of the Homo sapiens lineage, Omo I possesses unequivocal modern human characteristics, such as a tall and globular cranial vault and a chin," said co-author Dr Aurélien Mounier from the Musée de l'Homme in Paris. "The new date estimate, de facto, makes itthe oldest unchallenged Homo sapiens in Africa."

The researchers say that while this study shows a new minimum age for Homo sapiens in eastern Africa, it's possible that new finds and new studies may extend the age of our species even further back in time.

"We can only date humanity based on the fossils that we have, so it's impossible to say that this is the definitive age of our species," said Vidal. "The study of human evolution is always in motion: boundaries and timelines change as our understanding improves. But these fossils show just how resilient humans are: that we survived, thrived and migrated in an area that was so prone to natural disasters."

"It's probably no coincidence that our earliest ancestors lived in such a geologically active rift valley -- it collected rainfall in lakes, providing fresh water and attracting animals, and served as a natural migration corridor stretching thousands of kilometres," said Oppenheimer. "The volcanoes provided fantastic materials to make stone tools and from time to time we had to develop our cognitive skills when large eruptions transformed the landscape."

"Our forensic approach provides a new minimum age for Homo sapiens in eastern Africa, but the challenge still remains to provide a cap, a maximum age, for their emergence, which is widely believed to have taken place in this region," said co-author Professor Christine Lane, head of the Cambridge Tephra Laboratory where much of the work was carried out. "It's possible that new finds and new studies may extend the age of our species even further back in time."

Read more at Science Daily

Early modern human from Southeast Asia adapted to a rainforest environment

Traditional assumptions have often seen tropical rainforests as a barrier to early Homo sapiens. However, growing proof shows that humans adapted to and lived in tropical rainforest habitats of Southeast Asia. Some researchers also suggest that, in the past, other human species, like Homo erectus and Homo floresiensis, became extinct because they could not adapt to this environment as our species did. However, we know very little about the ecological adaptation of fossil humans, including what they were eating.

Zinc isotopes reveal what kind of food was primarily eaten

In this study, researchers analysed the zinc stable isotope ratios from animal and human teeth from two sites in the Huà Pan Province of Laos: Tam Pà Ling and the nearby site of Nam Lot. "The site of Tam Pà Ling is particularly important for palaeoanthropology and archaeology of Southeast Asia because it holds the oldest and most abundant fossil record of our species in this region," explains Fabrice Demeter, researcher at the University of Copenhagen. However, there is little archaeological evidence, like stone tools, hearth features, plant remains, cut marks on bones, in Tam Pà Ling: only teeth and bones. This makes isotopic approaches the only way to gain insight into past dietary reliance.

Nitrogen isotope analysis, in particular, can help scientists learn if past humans were eating animals or plants. However, the collagen in bones and teeth needed to do these analyses is not easily conservable. In tropical regions like the one at Tam Pà Ling this problem is even more acute. "New methods -- such as zinc isotope analysis of enamel -- can now overcome these limitations and allow us to investigate teeth from regions and periods we could not study before," says study leader Thomas Tütken, professor at the Johannes Gutenberg University's Institute of Geosciences. "With zinc stable isotope ratios, we can now study Tam Pà Ling and learn what kind of food our earliest ancestors in this region were eating."

First study that reveals the whole diet of fossil humans from Southeast Asia

The fossil human studied in this research dates from the Late Pleistocene, more precisely from 46,000 to 63,000 years ago. With it, various mammals from both sites, including water buffaloes, rhinos, wild boars, deer, bears, orangutans, macaques, and leopards, were also analysed. All these different animals show various eating behaviours, making for an ideal background to determine what exactly humans were eating at the time. The more diverse the animal remains found at a particular site are, the more information the researchers can use to understand the diet of prehistoric humans.

When we compare the zinc isotope values from the fossil Homo sapiens of Tam Pà Ling to that of the animals, it strongly suggests that its diet contained both plants and animals. This omnivorous diet also differs from most nitrogen isotope data of humans in other regions of the world for that time period, where a meat-rich diet is almost consistently discerned. "Another kind of analysis performed in this study -- stable carbon isotopes analysis -- indicates that the food consumed came strictly from forested environments," says Élise Dufour, researcher at the National Natural History Museum of Paris. "The results are the oldest direct evidence for subsistence strategies for Late Pleistocene humans in tropical rainforests."

Read more at Science Daily

Early human activities impacted Earth’s atmosphere more than previously known

Several years ago, while analyzing ice core samples from Antarctica's James Ross Island, scientists Joe McConnell, Ph.D., and Nathan Chellman, Ph.D., from DRI, and Robert Mulvaney, Ph.D., from the British Antarctic Survey noticed something unusual: a substantial increase in levels of black carbon that began around the year 1300 and continued to the modern day.

Black carbon, commonly referred to as soot, is a light-absorbing particle that comes from combustion sources such as biomass burning (e.g. forest fires) and, more recently, fossil fuel combustion. Working in collaboration with an international team of scientists from the United Kingdom, Austria, Norway, Germany, Australia, Argentina, and the U.S., McConnell, Chellman, and Mulvaney set out to uncover the origins of the unexpected increase in black carbon captured in the Antarctic ice.

The team's findings, which published this week in Nature, point to an unlikely source: ancient Maori land-burning practices in New Zealand, conducted at a scale that impacted the atmosphere across much of the Southern Hemisphere and dwarfed other preindustrial emissions in the region during the past 2,000 years.

"The idea that humans at this time in history caused such a significant change in atmospheric black carbon through their land clearing activities is quite surprising," said McConnell, research professor of hydrology at DRI who designed and led the study. "We used to think that if you went back a few hundred years you'd be looking at a pristine, pre-industrial world, but it's clear from this study that humans have been impacting the environment over the Southern Ocean and the Antarctica Peninsula for at least the last 700 years."

Tracing the black carbon to its source

To identify the source of the black carbon, the study team analyzed an array of six ice cores collected from James Ross Island and continental Antarctica using DRI's unique continuous ice-core analytical system. The method used to analyze black carbon in ice was first developed in McConnell's lab in 2007.

While the ice core from James Ross Island showed a notable increase in black carbon beginning around the year 1300, with levels tripling over the 700 years that followed and peaking during the 16th and 17th centuries, black carbon levels at sites in continental Antarctica during the same period of time stayed relatively stable.

Andreas Stohl, Ph.D., of the University of Vienna led atmospheric model simulations of the transport and deposition of black carbon around the Southern Hemisphere that supported the findings.

"From our models and the deposition pattern over Antarctica seen in the ice, it is clear that Patagonia, Tasmania, and New Zealand were the most likely points of origin of the increased black carbon emissions starting about 1300," said Stohl.

After consulting paleofire records from each of the three regions, only one viable possibility remained: New Zealand, where charcoal records showed a major increase in fire activity beginning about the year 1300. This date also coincided with the estimated arrival, colonization, and subsequent burning of much of New Zealand's forested areas by the Maori people.

This was a surprising conclusion, given New Zealand's relatively small land area and the distance (nearly 4,500 miles), that smoke would have travelled to reach the ice core site on James Ross Island.

Read more at Science Daily

Environmental conditions of early humans in Europe

Understanding the environmental conditions under which early humans dispersed out of Africa is important for understanding the factors that affected human evolution. This is a topical question that remains debated. A recent study prepared in collaboration with researchers from the University of Helsinki and the Universities of Granada, Tarragona, Zaragoza, Barcelona, Salamanca, Madrid and Tübingen provides new information on the environmental context of earliest human occupation in Europe during the Pleistocene.

The research is part of the Orce project (ProyectORCE) funded by the local government of Andalucía and led by the University of Granada, in which researchers from the University of Helsinki have been participating since 2017. The project is responsible for archeological/palaentological excavations and related research in Andalucía, Spain.

The study is focussed on the Guadix-Baza Basin, Andalucía, Spain, where the researchers used dental ecometric trait distribution within fossil large mammal communities to reconstruct climatic variables and net primary production of plant communities from ca. 4.5 million years to ca. 400,000 years ago.

The Guadix-Baza basin is of particular importance for understanding early human environments outside Africa, because it includes a couple of sites that are among the earliest human occupation sites in Europe, Barranco León and Fuente Nueva 3 near the city of Orce, which have been dated at ca. 1.4 -- 1.2 million years in age.

Based on the estimates, the climate in the Guadix-Baza Basin varied from roughly similar to present (e.g. Venta Micena, ca. 1.6 million years ago) to more humid, with higher annual primary production. The early human occupation sites in the Guadix-Baza Basin, such as Barranco León and Fuente Nueva 3, tended to have higher primary production than in the region today. The vegetation was mostly similar to Mediterranean forest without significant grassy undergrowth, making it different from African grass-dominated savanna environments.

Lead author Juha Saarinen from the University of Helsinki said: "Tooth wear-based dietary analyses indicate that most of the large herbivorous mammals in these environments did not consume significant amounts of grass, further attesting to the scarcity of grassy vegetation. This is an important finding, as it suggests that already the earliest human occupation sites in Europe were often different from African grassy savannas in terms of vegetation and interactions between large mammal fauna and vegetation."

The conditions under which early members of the genus Homo dispersed outside Africa were also analysed on a broader scale, across Europe during the Early and Middle Pleistocene. The model is based on the comparison of functional trait distribution of large herbivorous mammals in sites with archaeological or fossil evidence of human presence and in sites, which lack evidence of human presence.

Read more at Science Daily

Research 'final nail in the coffin' of Paranthropus as hard object feeders

New research from the University of Otago debunks a long-held belief about our ancestors' eating habits.

For more than 60 years, researchers have believed Paranthropus, a close fossil relative of ours which lived about one to three million years ago, evolved massive back teeth to consume hard food items such as seeds and nuts, while our own direct ancestors, the genus Homo, is thought to have evolved smaller teeth due to eating softer food such as cooked food and meats.

However, after travelling to several large institutes and museums in South Africa, Japan and the United Kingdom and studying tooth fractures in more than 20,000 teeth of fossil and living primate species, Dr Ian Towle, an Otago biological anthropologist, working with Dr Carolina Loch, of the Faculty of Dentistry, says this "neat picture is far more complex than once thought."

"By individually studying each tooth and recording the position and size of any tooth fractures, we show tooth chipping does not support regular hard food eating in Paranthropus robustus, therefore potentially putting an end to the argument that this group as a whole were hard food eaters," he says.

Dr Towle says the findings challenge our understanding of dietary and behavioural changes during human evolution.

"The results are surprising, with human fossils so far studied -- those in our own genus Homo -- showing extremely high rates of tooth fractures, similar to living hard object eating primates, yet Paranthropus show extremely low levels of fracture, similar to primates that eat soft fruits or leaves.

"Although in recent years there has been a slow acceptance that another species of Paranthropus, Paranthropus boisei, found in East Africa, was unlikely to have regularly eaten hard foods, the notion that Paranthropus evolved their large dental apparatus to eat hard foods has persisted. Therefore, this research can be seen as the final nail in the coffin of Paranthropus as hard object feeders."

The fact that humans show such contrasting chipping patterns is equally significant and will have "knock on" effects for further research, particularly research on dietary changes during human evolution, and why the human dentition has evolved the way it has, he says.

"The regular tooth fractures in fossil humans may be caused by non-food items, such as grit or stone tools. However, regardless of the cause, these groups were subjected to substantial tooth wear and fractures. So, it raises questions to why our teeth reduced in size, especially compared to groups like Paranthropus."

Dr Towle's research will now focus on if our dentition evolved smaller due to other factors to allow other parts of the skull to expand, leading to evolution then favouring other tooth properties to protect it against wear and fracture, instead of increased tooth size.

"This is something we are investigating now, to see if tooth enamel may have evolved different characteristics among the great apes. Our research as a whole may also have implications for our understanding of oral health, since fossil human samples typically show immaculate dental health.

Read more at Science Daily

Global climate dynamics drove the decline of mastodonts and elephants, new study suggests

Elephants and their forebears were pushed into wipeout by waves of extreme global environmental change, rather than overhunting by early humans, according to new research.

The study, published today in Nature Ecology & Evolution, challenges claims that early human hunters slaughtered prehistoric elephants, mammoths and mastodonts to extinction over millennia. Instead, its findings indicate the extinction of the last mammoths and mastodonts at the end of the last Ice Age marked the end of progressive climate-driven global decline among elephants over millions of years.

Although elephants today are restricted to just three endangered species in the African and Asian tropics, these are survivors of a once far more diverse and widespread group of giant herbivores, known as the proboscideans, which also include the now completely extinct mastodonts, stegodonts and deinotheres. Only 700,000 years ago, England was home to three types of elephants: two giant species of mammoths and the equally prodigious straight-tusked elephant.

An international group of palaeontologists from the universities of Alcalá, Bristol, and Helsinki, piloted the most detailed analysis to date on the rise and fall of elephants and their predecessors, which examined how 185 different species adapted, spanning 60 million years of evolution that began in North Africa. To probe into this rich evolutionary history, the team surveyed museum fossil collections across the globe, from London's Natural History Museum to Moscow's Paleontological Institute. By investigating traits such as body size, skull shape and the chewing surface of their teeth, the team discovered that all proboscideans fell within one of eight sets of adaptive strategies.

"Remarkably for 30 million years, the entire first half of proboscidean evolution, only two of the eight groups evolved," said Dr Zhang Hanwen, study coauthor and Honorary Research Associate at the University of Bristol's School of Earth Sciences.

"Most proboscideans over this time were nondescript herbivores ranging from the size of a pug to that of a boar. A few species got as big as a hippo, yet these lineages were evolutionary dead-ends. They all bore little resemblance to elephants."

The course of proboscidean evolution changed dramatically some 20 million years ago, as the Afro-Arabian plate collided into the Eurasian continent. Arabia provided crucial migration corridor for the diversifying mastodont-grade species to explore new habitats in Eurasia, and then into North America via the Bering Land Bridge.

"The immediate impact of proboscidean dispersals beyond Africa was quantified for the very first time in our study," said lead author Dr Juan Cantalapiedra, Senior Research Fellow at the University of Alcalá in Spain.

"Those archaic North African species were slow-evolving with little diversification, yet we calculated that once out of Africa proboscideans evolved 25 times faster, giving rise to a myriad of disparate forms, whose specialisations permitted niche partition between several proboscidean species in the same habitats. One case in point being the massive, flattened lower tusks of the 'shovel-tuskers'. Such coexistence of giant herbivores was unlike anything in today's ecosystems."

Dr Zhang added: "The aim of the game in this boom period of proboscidean evolution was 'adapt or die'. Habitat perturbations were relentless, pertained to the ever-changing global climate, continuously promoting new adaptive solutions while proboscideans that didn't keep up were literally, left for dead. The once greatly diverse and widespread mastodonts were eventually reduced to less than a handful of species in the Americas, including the familiar Ice Age American mastodon."

By 3 million years ago the elephants and stegodonts of Africa and eastern Asia seemingly emerged victorious in this unremitting evolutionary ratchet. However, environmental disruption connected to the coming Ice Ages hit them hard, with surviving species forced to adapt to the new, more austere habitats. The most extreme example was the woolly mammoth, with thick, shaggy hair and big tusks for retrieving vegetation covered under thick snow.

The team's analyses identified final proboscidean extinction peaks starting at around 2.4 million years ago, 160,000 and 75,000 years ago for Africa, Eurasia and the Americas, respectively.

"It is important to note that these ages do not demarcate the precise timing of extinctions, but rather indicate the points in time at which proboscideans on the respective continents became subject to higher extinction risk," said Dr Cantalapiedra.

Unexpectedly, the results do not correlate with the expansion of early humans and their enhanced capabilities to hunt down megaherbivores.

"We didn't foresee this result. It appears as if the broad global pattern of proboscidean extinctions in recent geological history could be reproduced without accounting for impacts of early human diasporas. Conservatively, our data refutes some recent claims regarding the role of archaic humans in wiping out prehistoric elephants, ever since big game hunting became a crucial part of our ancestors' subsistence strategy around 1.5 million years ago," said Dr Zhang.

Read more at Science Daily

A new type of Homo unknown to science

Researchers from Tel Aviv University and the Hebrew University of Jerusalem have identified a new type of early human at the Nesher Ramla site, dated to 140,000 to 120,000 years ago. According to the researchers, the morphology of the Nesher Ramla humans shares features with both Neanderthals (especially the teeth and jaws) and archaic Homo (specifically the skull). At the same time, this type of Homo is very unlike modern humans -- displaying a completely different skull structure, no chin, and very large teeth. Following the study's findings, researchers believe that the Nesher Ramla Homo type is the 'source' population from which most humans of the Middle Pleistocene developed. In addition, they suggest that this group is the so-called 'missing' population that mated with Homo sapiens who arrived in the region around 200,000 years ago -- about whom we know from a recent study on fossils found in the Misliya cave.

Two teams of researchers took part in the dramatic discovery, published in the journal Science: an anthropology team from Tel Aviv University headed by Prof. Israel Hershkovitz, Dr. Hila May and Dr. Rachel Sarig from the Sackler Faculty of Medicine and the Dan David Center for Human Evolution and Biohistory Research and the Shmunis Family Anthropology Institute, situated in the Steinhardt Museum at Tel Aviv University; and an archaeological team headed by Dr. Yossi Zaidner from the Institute of Archaeology at the Hebrew University of Jerusalem.

Timeline: The Nesher Ramla Homo type was an ancestor of both the Neanderthals in Europe and the archaic Homo populations of Asia.

Prof. Israel Hershkovitz: "The discovery of a new type of Homo" is of great scientific importance. It enables us to make new sense of previously found human fossils, add another piece to the puzzle of human evolution, and understand the migrations of humans in the old world. Even though they lived so long ago, in the late middle Pleistocene (474,000-130,000 years ago), the Nesher Ramla people can tell us a fascinating tale, revealing a great deal about their descendants' evolution and way of life."

The important human fossil was found by Dr. Zaidner of the Hebrew University during salvage excavations at the Nesher Ramla prehistoric site, in the mining area of the Nesher cement plant (owned by Len Blavatnik) near the city of Ramla. Digging down about 8 meters, the excavators found large quantities of animal bones, including horses, fallow deer and aurochs, as well as stone tools and human bones. An international team led by the researchers from Tel Aviv and Jerusalem identified the morphology of the bones as belonging to a new type of Homo, previously unknown to science. This is the first type of Homo to be defined in Israel, and according to common practice, it was named after the site where it was discovered -- the Nesher Ramla Homo type.

Dr. Yossi Zaidner: "This is an extraordinary discovery. We had never imagined that alongside Homo sapiens, archaic Homo roamed the area so late in human history. The archaeological finds associated with human fossils show that "Nesher Ramla Homo" possessed advanced stone-tool production technologies and most likely interacted with the local Homo sapiens." The culture, way of life, and behavior of the Nesher Ramla Homo are discussed in a companion paper also published in Science journal today.

Prof. Hershkovitz adds that the discovery of the Nesher Ramla Homo type challenges the prevailing hypothesis that the Neanderthals originated in Europe. "Before these new findings," he says, "most researchers believed the Neanderthals to be a 'European story', in which small groups of Neanderthals were forced to migrate southwards to escape the spreading glaciers, with some arriving in the Land of Israel about 70,000 years ago. The Nesher Ramla fossils make us question this theory, suggesting that the ancestors of European Neanderthals lived in the Levant as early as 400,000 years ago, repeatedly migrating westward to Europe and eastward to Asia. In fact, our findings imply that the famous Neanderthals of Western Europe are only the remnants of a much larger population that lived here in the Levant -- and not the other way around."

According to Dr. Hila May, despite the absence of DNA in these fossils, the findings from Nesher Ramla offer a solution to a great mystery in the evolution of Homo: How did genes of Homo sapiens penetrate the Neanderthal population that presumably lived in Europe long before the arrival of Homo sapiens? Geneticists who studied the DNA of European Neanderthals have previously suggested the existence of a Neanderthal-like population which they called the 'missing population' or the 'X population' that had mated with Homo sapiens more than 200,000 years ago. In the anthropological paper now published in Science, the researchers suggest that the Nesher Ramla Homo type might represent this population, heretofore missing from the record of human fossils. Moreover, the researchers propose that the humans from Nesher Ramla are not the only ones of their kind discovered in the region, and that some human fossils found previously in Israel, which have baffled anthropologists for years -- like the fossils from the Tabun cave (160,000 years ago), Zuttiyeh cave (250,000), and Qesem cave (400,000) -- belong to the same new human group now called the Nesher Ramla Homo type.

"People think in paradigms," says Dr. Rachel Sarig. "That's why efforts have been made to ascribe these fossils to known human groups like Homo sapiens, Homo erectus, Homo heidelbergensis or the Neanderthals. But now we say: No. This is a group in itself, with distinct features and characteristics. At a later stage small groups of the Nesher Ramla Homo type migrated to Europe -- where they evolved into the 'classic' Neanderthals that we are familiar with, and also to Asia, where they became archaic populations with Neanderthal-like features. As a crossroads between Africa, Europe and Asia, the Land of Israel served as a melting pot where different human populations mixed with one another, to later spread throughout the Old World. The discovery from the Nesher Ramla site writes a new and fascinating chapter in the story of humankind."

Read more at Science Daily

Genomes of the earliest Europeans

An international research team has sequenced the genomes of the oldest securely dated modern humans in Europe who lived around 45,000 years ago in Bacho Kiro Cave, Bulgaria. By comparing their genomes to the genomes of people who lived later in Europe and in Asia the researchers from the Max Planck Institute for Evolutionary Anthropology in Leipzig, Germany, show that this early human group in Europe contributed genes to later people, particularly present-day East Asians. The researchers also identified large stretches of Neanderthal DNA in the genomes of the Bacho Kiro Cave people, showing that they had Neanderthal ancestors about five to seven generations back in their family histories. This suggests that mixture with Neanderthals was the rule rather than the exception when the first modern humans arrived in Europe.

Last year, a research team led by researchers from the National Institute of Archaeology with Museum at the Bulgarian Academy of Sciences and the Max Planck Institute for Evolutionary Anthropology, Germany, reported the discovery of modern human remains found in direct association with the Initial Upper Palaeolithic stone tools at the site of Bacho Kiro Cave in Bulgaria. The oldest individuals found in the cave were directly radiocarbon dated to between 43,000 and 46,000 years ago. They are thus the earliest known dispersal of modern humans across the mid-latitudes of Eurasia.

Mateja Hajdinjak and colleagues have now sequenced the genomes of five individuals found at the Bacho Kiro Cave. Four individuals are between 43,000 to 46,000-years-old and were found together with stone tools belonging to the Initial Upper Palaeolithic, the earliest culture associated with modern humans in Eurasia. An additional individual found in the cave is around 35,000-years-old and found with stone tools of a later type. It was previously thought that bearers of the Initial Upper Palaeolithic died out without contributing genetically to modern humans arriving later. However, the researchers now show that the oldest Bacho Kiro Cave individuals, or groups closely related to them, contributed genes to present-day people. Surprisingly, this contribution is found particularly in East Asia and the Americas rather than in Europe where the Bacho Kiro Cave people lived. These genetic links to Asia mirror the links seen between the Initial Upper Palaeolithic stone tools and personal ornaments found in Bacho Kiro Cave and tools and ancient jewelry found across Eurasia to Mongolia.

Genetic differences between individuals

Importantly, the later 35,000-year-old individual found in Bacho Kiro Cave belonged to a group that was genetically distinct from the earlier inhabitants of the cave. This shows that the earliest history of modern humans in Europe may have been tumultuous and involved population replacements.

The earliest people at Bacho Kiro Cave lived at a time when Neanderthals were still around. The researchers therefore scanned their genomes for fragments of Neanderthal DNA. "We found that the Bacho Kiro Cave individuals had higher levels of Neanderthal ancestry than nearly all other early humans, with the exception of a 40,000-year-old individual from Romania. Crucially, most of this Neanderthal DNA comes in extremely long stretches. This shows that these individuals had Neanderthal ancestors some five to seven generations back in their family trees" says Mateja Hajdinjak.

 Read more at Science Daily