Smallest arm bone in human fossil record sheds light on the dawn of Homo floresiensis

A paper out today in Nature Communications reports the discovery of extremely rare early human fossils from the Indonesian island of Flores, including an astonishingly small adult limb bone.

Dated to about 700,000 years old, the new findings shed light on the evolution of Homo floresiensis, the so-called 'Hobbits' of Flores whose remains were uncovered in 2003 at Liang Bua cave in the island's west by a team co-led by Australian-New Zealand archaeologist Professor Mike Morwood (1950-2013).

Archaeological evidence suggests these diminutive, small-brained humans inhabited Liang Bua as recently as 50,000 years ago, a time when our own species (Homo sapiens) was already long established in Australia to the south.

There has been much debate about the origin of the mysterious humans from Flores. It was first hypothesised that Homo floresiensis was a dwarfed descendant of early Asian Homo erectus.

Another theory is that the 'Hobbit' is a late-surviving remnant of a more ancient hominin from Africa that pre-dates Homo erectus and was small in stature to begin with, in which case possible candidates include Homo habilis or the famous 'Lucy' (Australopithecus afarensis).

Other than Liang Bua, hominin fossils have only ever been found at a single location on Flores: the open-air site of Mata Menge 75km to the east of the cave. Located in the sparsely populated tropical grasslands of the So'a Basin, this site has previously yielded several hominin fossils (a jaw fragment and six teeth) excavated from a layer of sandstone laid down by a small stream around 700,000 years ago.

Pre-dating the Liang Bua hominins by 650,000 years, the Mata Menge fossil remains have been shown to belong to at least three individuals with even slightly smaller jaws and teeth than Homo floresiensis, implying that small body size evolved early in the history of Flores hominins.

However, as postcranial elements (bones from below the head) had not been found in the fossil record at this site it could not be confirmed that these So'a Basin hominins were at least as small as, if not slightly smaller than, Homo floresiensis.

It was also unclear what species the Mata Menge fossils belonged to, owing to the lack of more diagnostic specimens. However, some teeth were deemed to be intermediate in form between those of early Asian Homo erectus and Homo floresiensis.

The new study published in Nature Communications was led by Professor Yousuke Kaifu of the University of Tokyo, Iwan Kurniawan of the Center for Geological Survey in Indonesia, and Associate Professor Gerrit van den Bergh from the University of Wollongong.

It reports the discovery of three additional hominin fossils from Mata Menge dating to 700,000 years ago, the outcome of several field seasons of excavations at this site. Most importantly, the new assemblage includes the first postcranial element, a distal shaft of an adult humerus (lower half of the upper arm bone).

The recovery of a fossil limb bone from the Mata Menge excavation site has been long-awaited because of the wealth of evidence it provides regarding the ancestral origin of Homo floresiensis.

Digital microscopy of the microstructure indicates that the small humerus is from an adult individual. Based on the estimated length of the bone, the team was able to calculate the body height of this hominin to be about 100cm tall. This is around 6cm shorter than the estimated body height of the 60,000-year-old Homo floresiensis skeleton from Liang Bua (~106cm, based on the femoral length).

"This 700,000-year-old adult humerus is not just shorter than that of Homo floresiensis, it is the smallest upper arm bone known from the hominin fossil record worldwide," said Professor Adam Brumm from Griffith University's Australian Research Centre for Human Evolution, a co-author of the paper.

"This very rare specimen confirms our hypothesis that the ancestors of Homo floresiensis were extremely small in body size; however, it is now apparent from the tiny proportions of this limb bone that the early progenitors of the 'Hobbit' were even smaller than we had previously thought."

The two additional hominin teeth from Mata Menge are also small in size and one bears shape characteristics that are most consistent with early Homo erectus of Java. This similarity does not support the hypothesis that Homo floresiensis evolved from an earlier and more primitive type of hominin, the likes of which have never been recovered from Indonesia, or indeed the wider region outside Africa.

The Mata Menge human remains, which now total 10 fossil specimens, are from at least four individuals (including two children). All of them are very similar anatomically to the Liang Bua Homo floresiensis and can now be regarded as an older variant of this hominin. However, while a direct ancestor of the 'Hobbit', this earlier form had a less specialised dentition (more primitive teeth) than its descendant at Liang Bua.

Further, it is evident from the tiny arm bone that extreme body size reduction occurred early in the history of the Flores hominins.

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Interspecies competition led to even more forms of ancient human -- defying evolutionary trends in vertebrates

Competition between species played a major role in the rise and fall of hominins -- and produced a "bizarre" evolutionary pattern for the Homo lineage -- according to a new University of Cambridge study that revises the start and end dates for many of our early ancestors.

Conventionally, climate is held responsible for the emergence and extinction of hominin species. In most vertebrates, however, interspecies competition is known to play an important role.

Now, research shows for the first time that competition was fundamental to "speciation" -- the rate at which new species emerge -- across five million years of hominin evolution.

The study, published today in Nature Ecology & Evolution, also suggests that the species formation pattern of our own lineage was unlike almost anything else.

"We have been ignoring the way competition between species has shaped our own evolutionary tree," said lead author Dr Laura van Holstein, a University of Cambridge biological anthropologist from Clare College. "The effect of climate on hominin species is only part of the story."

In other vertebrates, species form to fill ecological "niches" says van Holstein. Take Darwin's finches: some evolved large beaks for nut-cracking, while others evolved small beaks for feeding on certain insects. When each resource niche gets filled, competition kicks in, so no new finches emerge and extinctions take over.

Van Holstein used Bayesian modelling and phylogenetic analyses to show that, like other vertebrates, most hominin species formed when competition for resources or space were low.

"The pattern we see across many early hominins is similar to all other mammals. Speciation rates increase and then flatline, at which point extinction rates start to increase. This suggests that interspecies competition was a major evolutionary factor."

However, when van Holstein analysed our own group, Homo, the findings were "bizarre."

For the Homo lineage that led to modern humans, evolutionary patterns suggest that competition between species actually resulted in the appearance of even more new species -- a complete reversal of the trend seen in almost all other vertebrates.

"The more species of Homo there were, the higher the rate of speciation. So when those niches got filled, something drove even more species to emerge. This is almost unparalleled in evolutionary science."

The closest comparison she could find was in beetle species that live on islands, where contained ecosystems can produce unusual evolutionary trends.

"The patterns of evolution we see across species of Homo that led directly to modern humans is closer to those of island-dwelling beetles than other primates, or even any other mammal."

Recent decades have seen the discovery of several new hominin species, from Australopithecus sediba to Homo floresiensis. Van Holstein created a new database of "occurrences" in the hominin fossil record: each time an example of a species was found and dated, around 385 in total.

Fossils can be an unreliable measure of species' lifetimes. "The earliest fossil we find will not be the earliest members of a species," said van Holstein.

"How well an organism fossilises depends on geology, and on climatic conditions: whether it is hot or dry or damp. With research efforts concentrated in certain parts of the world, and we might well have missed younger or older fossils of a species as a result."

Van Holstein used data modelling to address this problem, and factor in likely numbers of each species at the beginning and end of their existence, as well as environmental factors on fossilisation, to generate new start and end dates for most known hominin species (17 in total).

She found that some species thought to have evolved through "anagenesis" -- when one slowly turns into another, but lineage doesn't split -- may have actually "budded": when a new species branches off from an existing one.*

This meant that several more hominin species than previously assumed were co-existing, and so possibly competing.

While early species of hominins, such as Paranthropus, probably evolved physiologically to expand their niche -- adapting teeth to exploit new types of food, for example -- the driver of the very different pattern in our own genus Homo may well have been technology.

"Adoption of stone tools or fire, or intensive hunting techniques, are extremely flexible behaviours. A species that can harness them can quickly carve out new niches, and doesn't have to survive vast tracts of time while evolving new body plans," said van Holstein

She argues that an ability to use technology to generalise, and rapidly go beyond ecological niches that force other species to compete for habitat and resources, may be behind the exponential increase in the number of Homo species detected by the latest study.

But it also led to Homo sapiens -- the ultimate generalisers. And competition with an extremely flexible generalist in almost every ecological niche may be what contributed to the extinction of all other Homo species.

Added van Holstein: "These results show that, although it has been conventionally ignored, competition played an important role in human evolution overall. Perhaps most interestingly, in our own genus it played a role unlike that across any other vertebrate lineage known so far."

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No scientific evidence for cognitively advanced behaviors and symbolism by Homo naledi

A new study has cast doubt on claims that Homo naledi, a small-brained hominin dating to between 335-241,000 years ago, deliberately buried their dead and produced rock art in Rising Star Cave, South Africa.

Three pre-print articles published this year in eLife suggested the recent excavations at the Rising Star Cave system provided evidence of at least three burial features, two in the Dinaledi Chamber and a third in the Hill Antechamber cavity.

The articles claimed the features represented the earliest evidence of deliberate burial by a hominin species, and that Homo naledi lit up dark passageways using fire and intentionally carried the bodies of at least three individuals deep inside the Rising Star Cave system, dug pits, deposited corpses inside the pits, and covered the bodies with sediments.

It was also claimed that the Hill Antechamber feature contained a stone tool in close proximity to the hominin hand.

However, a group of  experts with specialisations in biological anthropology, archaeology, geochronology, and rock art, have now called for a deeper dig into the science behind the findings in a first, peer-reviewed critique published in the Journal of Human Evolution (JHE).

Professor Michael Petraglia from Griffith University's Australian Research Centre for Human Evolution, Professor Andy Herries from La Trobe University, María Martinón-Torres from the National Research Center on Human Evolution in Spain and Diego Garate from the University of Cantabria in Spain co-authored the peer-reviewed article.

The research team conclude the evidence presented so far was not compelling enough to support the deliberate burial of the dead by Homo naledi, nor that they made the purported engravings.

"We really need substantial additional documentation and scientific analyses before we can rule out that natural agents and post-depositional processes were responsible for the accumulation of bodies/body parts and to prove the intentional excavation and filling of pits by Homo naledi," Professor Martinón-Torres said.

Moreover, Professor Petraglia added: "Unfortunately, there is a distinct possibility that the so-called stone artifact next to the hominin hand is a geofact, and not a product of stone tool flaking by Homo naledi."

Professor Herries said: "There is no evidence that Homo naledi lit fires in the cave, purported buring locations could just be from manganese staining and charcoal within the cave remains to be dated. Charcoal from natural fires is not uncommon in caves."

"Detailed analyses are also needed to demonstrate that the so-called 'engravings' are indeed human-made marks, as marks like these can be produced as a product of natural weathering or animal claws," said Dr Garate.

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Key role of ice age cycles in early human interbreeding

A study published in Science indicates that climatic shifts over the past 400,000 years have influenced Neanderthal and Denisovan interbreeding.

Recent paleogenomic research revealed that interbreeding was common among early human species. However, little was known about when, where, and how often this hominin interbreeding took place. Using paleoanthropological evidence, genetic data, and supercomputer simulations of past climate, a team of international researchers has found that interglacial climates and corresponding shifts in vegetation created common habitats for Neanderthals and Denisovans, increasing their chances for interbreeding and gene flow in parts of Europe and central Asia.

Contemporary humans carry in their cells a small amount of DNA derived from Neanderthals and Denisovans. "Denny," a 90,000-year-old fossil individual, recently identified as the daughter of a Denisovan father and a Neanderthal mother, bears testimony to the possibility that interbreeding was quite common among early human species. But when, where, and at what frequency did this interbreeding take place?

In a recent study published in Science on 10 August 2023, researchers from Korea and Italy have joined hands to answer this question. Using fossil data, supercomputer simulations of past climate, and insights obtained from genomic evidence, the team was able to identify habitat overlaps and contact hotspots of these early human species. Dr. Jiaoyang Ruan, Postdoctoral Researcher at IBS Center for Climate Physics (ICCP), South Korea, explains, "Little is known about when, where, and how frequently Neanderthals and Denisovans interbred throughout their shared history. As such, we tried to understand the potential for Neanderthal-Denisovan admixture using species distribution models that bring extensive fossil, archeological, and genetic data together with transient Coupled General Circulation Model simulations of global climate and biome."

The researchers found that Neanderthals and Denisovans had different environmental preferences to start with. While Denisovans were much more adapted to colder environments, such as the boreal forests and the tundra region in northeastern Eurasia, their Neanderthal cousins preferred the warmer temperate forests and grasslands in the southwest. However, shifts in the Earth's orbit led to changes in climatic conditions and hence vegetation patterns. This triggered the migration of both these hominin species towards geographically overlapping habitats, thus increasing the chance of their interbreeding.

The researchers further used insights gained from their analysis to determine the contact hotspots between Neanderthals and Denisovans. They identified Central Eurasia, the Caucasus, the Tianshan, and the Changbai mountains as the likely hotspots. Identification of these habitat overlaps also helped the researchers place 'Denny' within the climatic context and even confirmed the other known episodes of genetic interbreeding. The researchers also noted that the Denisovans and Neanderthals would have had a high probability of contact in the Siberian Altai during ~ 340-290, ~240-190 and ~130-80 thousand years ago.

To further elucidate the factors that triggered the 'east-west interbreeding seesaw,' the team examined the change in vegetation patterns over Eurasia over the past 400 thousand years. They observed that elevated atmospheric CO2 concentrations and mild interglacial conditions caused an eastward expansion of the temperate forest into central Eurasia, and the dispersal of Neanderthals into Denisovan lands. On the contrary, lower CO2 concentrations and corresponding harsher glacial climate potentially caused a fragmentation of their habitats, leading to lesser interactions and interbreeding events.

"Pronounced climate-driven zonal shifts in the main overlap region of Denisovans and Neanderthals in central Eurasia, which can be attributed to the response of climate and vegetation to past variations in atmospheric CO2 and northern hemisphere ice-sheet volume, influenced the timing and intensity of potential interbreeding events," remarks senior author Axel Timmermann, Director, ICCP and Professor at Pusan National University, South Korea.

Read more at Science Daily

First hominin muscle reconstruction shows 3.2 million-year-old 'Lucy' could stand as erect as we can

A Cambridge University researcher has digitally reconstructed the missing soft tissue of an early human ancestor -- or hominin -- for the first time, revealing a capability to stand as erect as we do today.

Dr Ashleigh Wiseman has 3D-modelled the leg and pelvis muscles of the hominin Australopithecus afarensis using scans of 'Lucy': the famous fossil specimen discovered in Ethiopia in the mid-1970s.

Australopithecus afarensis was an early human species that lived in East Africa over three million years ago. Shorter than us, with an ape-like face and smaller brain, but able to walk on two legs, it adapted to both tree and savannah dwelling -- helping the species survive for almost a million years.

Named for the Beatles classic 'Lucy in the Sky with Diamonds', Lucy is one of the most complete examples to be unearthed of any type of Australopithecus -- with 40% of her skeleton recovered.

Wiseman was able to use recently published open source data on the Lucy fossil to create a digital model of the 3.2 million-year-old hominin's lower body muscle structure. The study is published in the journal Royal Society Open Science.

The research recreated 36 muscles in each leg, most of which were much larger in Lucy and occupied greater space in the legs compared to modern humans.

For example, major muscles in Lucy's calves and thighs were over twice the size of those in modern humans, as we have a much higher fat to muscle ratio. Muscles made up 74% of the total mass in Lucy's thigh, compared to just 50% in humans.

Paleoanthropologists agree that Lucy was bipedal, but disagree on how she walked. Some have argued that she moved in a crouching waddle, similar to chimpanzees -- our common ancestor -- when they walk on two legs. Others believe that her movement was closer to our own upright bipedalism.

Research in the last 20 years have seen a consensus begin to emerge for fully erect walking, and Wiseman's work adds further weight to this. Lucy's knee extensor muscles, and the leverage they would allow, confirm an ability to straighten the knee joints as much as a healthy person can today.

"Lucy's ability to walk upright can only be known by reconstructing the path and space that a muscle occupies within the body," said Wiseman, from Cambridge University's McDonald Institute for Archaeological Research.

"We are now the only animal that can stand upright with straight knees. Lucy's muscles suggest that she was as proficient at bipedalism as we are, while possibly also being at home in the trees. Lucy likely walked and moved in a way that we do not see in any living species today," Wiseman said.

"Australopithecus afarensis would have roamed areas of open wooded grassland as well as more dense forests in East Africa around 3 to 4 million years ago. These reconstructions of Lucy's muscles suggest that she would have been able to exploit both habitats effectively."

Lucy was a young adult, who stood at just over one metre tall and probably weighed around 28kg. Lucy's brain would have been roughly a third of the size of ours.

To recreate the muscles of this hominin, Wiseman started with some living humans. Using MRI and CT scans of the muscle and bone structures of a modern woman and man, she was able to map the "muscle paths" and build a digital musculoskeletal model.

Wiseman then used existing virtual models of Lucy's skeleton to "rearticulate" the joints -- that is, put the skeleton back together. This work defined the axis from which each joint was able to move and rotate, replicating how they moved during life.

Finally, muscles were layered on top, based on pathways from modern human muscle maps, as well as what little "muscle scarring" was discernible (the traces of muscle connection detectable on the fossilised bones). "Without open access science, this research would not have been possible," said Wiseman.

Read more at Science Daily

Surprising similarities in stone tools of early humans and monkeys

Researchers from the Max Planck Institute for Evolutionary Anthropology have discovered artefacts produced by old world monkeys in Thailand that resemble stone tools, which historically have been identified as intentionally made by early hominins. Until now, sharp-edged stone tools were thought to represent the onset of intentional stone tool production, one of the defining and unique characteristics of hominin evolution. This new study challenges long held beliefs about the origins of intentional tool production in our own lineage.

The research is based on new analyses of stone tools used by long-tailed macaques in the Phang Nga National Park in Thailand. These monkeys use stone tools to crack open hard-shelled nuts. In that process, the monkeys often break their hammerstones and anvils. The resulting assemblage of broken stones is substantial and widespread across the landscape. Moreover, many of these artefacts bear all of the same characteristics that are commonly used to identify intentionally made stone tools in some of the earliest archaeological sites in East Africa.

"The ability to intentionally make sharp stone flakes is seen as a crucial point in the evolution of hominins, and understanding how and when this occurred is a huge question that is typically investigated through the study of past artefacts and fossils. Our study shows that stone tool production is not unique to humans and our ancestors," says lead author Tomos Proffitt, a researcher at the Max Planck Institute for Evolutionary Anthropology. "The fact that these macaques use stone tools to process nuts is not surprising, as they also use tools to gain access to various shellfish as well. What is interesting is that, in doing so they accidently produce a substantial archaeological record of their own that is partly indistinguishable from some hominin artefacts."

New insights into the evolution of stone tool technology

By comparing the accidentally produced stone fragments made by the macaques with those from some of the earliest archaeological sites, the researchers were able to show that many of the artefacts produced by monkeys fall within the range of those commonly associated with early hominins. Co-lead author Jonathan Reeves highlights: "The fact that these artifacts can be produced through nut cracking has implications for the range of behaviours we associate with sharp edged flakes in the archaeological record.."

The newly discovered macaque stone tools offer new insights into how the first technology might have started in our earliest ancestors and that its origin may have been linked to similar nut cracking behaviour which could be substantially older than the current earliest archaeological record. "Cracking nuts using stone hammers and anvils, similar to what some primates do today, has been suggested by some as a possible precursor to intentional stone tool production. This study, along with previous ones published by our group, opens the door to being able to identify such an archaeological signature in the future," says Lydia Luncz, senior author of the study and head of the Technological Primates Research Group at the Max Planck Institute for Evolutionary Anthropology. "This discovery shows how living primates can help researchers investigate the origin and evolution of tool use in our own lineage."

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Waxing and waning of environment influences hominin dispersals across ancient Iran

A world-first model of paleoclimate and hydrology in Iran has highlighted favourable routes for Neanderthals and modern human expansions eastwards into Asia.

Published in PLOS ONE, the findings reveal for the first time that multiple humid periods in ancient Iran led to the expansions of human populations, opening dispersal route across the region, and the possible interactions of species such as Neanderthals and our own Homo sapiens.

Professor Michael Petraglia, a key researcher in the study, said historic humid periods resulted in massive changes to ecosystems and led the team to identify large lakes in areas that were formerly deserts.

"Conversely, during glacial periods this increased aridity would have led to the expansion of deserts, led to contractions, and the isolation of hominin populations," said Professor Petraglia, who is the Director of Griffith's Australian Research Centre for Human Evolution.

"This cycle of wetting and drying is shown for the first time in Iran."

The research team, led by PhD candidate Mohammad Javad Shoaee from the Max Planck Institute for Geoanthropology in Germany, found that during Marine Isotope Stage (MIS) 5, a warm, humid period beginning roughly 130,000 years ago, lakes and rivers enabled two pathways for human groups.

One was a northern route through the Alborz and Kopet Dagh Mountains and north of the Dasht-I Kavir desert. The other route, first identified here, ran south along the Zagros Mountains before extending eastwards towards Pakistan and Afghanistan.

The researchers also found evidence for a potential northern route during MIS 3, beginning about 57,000 years ago, which, given artifacts attributed to multiple tool making groups, could have permitted interactions between modern humans and Neanderthals.

"These findings highlight the importance of Iran for our species' dispersals out of Africa and ultimately around the globe," said Professor Petraglia.

"As in other regions long considered too arid for early human occupations, such as the Arabian Peninsula, recent palaeoclimatic research is changing how we understand the human story and the role that changing climates have played."

"We recognised a new southern route along the Zagros Mountains and extending eastwards towards Pakistan and Afghanistan. We found evidence for a potential northern route during MIS 3, which would have permitted hominin movements and species interactions in Southwest Asia," Shoaee said.

To find out how human groups made their way into Iran, the team developed the first spatially comprehensive, high resolution palaeohydrological model for Iran.

They then compared their model, which showed when and where water was available, to the distribution of previously documented archaeological sites.

The result was a clear relationship between the availability of water and the evidence of human presence.

Not only does the current study help to explain the presence of previously documented sites, it also serves as a guide for future archaeological surveys in the region.

"Our paleohydrological analyses identified 145,354km of rivers and 115 paleolakes calculated from 6380 paleolake deposits. Only a handful of these paleolakes have so far been studied," Shoaee said.

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2.9-million-year-old butchery site reopens case of who made first stone tools

Along the shores of Africa's Lake Victoria in Kenya roughly 2.9 million years ago, early human ancestors used some of the oldest stone tools ever found to butcher hippos and pound plant material, according to new research led by scientists with the Smithsonian's National Museum of Natural History and Queens College, CUNY, as well as the National Museums of Kenya, Liverpool John Moores University and the Cleveland Museum of Natural History.

The study, published today, Feb. 9, in the journal Science, presents what are likely to be the oldest examples of a hugely important stone-age innovation known to scientists as the Oldowan toolkit, as well as the oldest evidence of hominins consuming very large animals. Though multiple lines of evidence suggest the artifacts are likely to be about 2.9 million years old, the artifacts can be more conservatively dated to between 2.6 and 3 million years old, said lead study author Thomas Plummer of Queens College, research associate in the scientific team of the Smithsonian's Human Origins Program.

Excavations at the site, named Nyayanga and located on the Homa Peninsula in western Kenya, also produced a pair of massive molars belonging to the human species' close evolutionary relative Paranthropus. The teeth are the oldest fossilized Paranthropus remains yet found, and their presence at a site loaded with stone tools raises intriguing questions about which human ancestor made those tools, said Rick Potts, senior author of the study and the National Museum of Natural History's Peter Buck Chair of Human Origins.

"The assumption among researchers has long been that only the genus Homo, to which humans belong, was capable of making stone tools," Potts said. "But finding Paranthropus alongside these stone tools opens up a fascinating whodunnit."

Whichever hominin lineage was responsible for the tools, they were found more than 800 miles from the previously known oldest examples of Oldowan stone tools -- 2.6-million-year-old tools unearthed in Ledi-Geraru, Ethiopia. This greatly expands the area associated with Oldowan technology's earliest origins. Further, the stone tools from the site in Ethiopia could not be tied to any particular function or use, leading to speculation about what the Oldowan toolkit's earliest uses might have been.

Through analysis of the wear patterns on the stone tools and animal bones discovered at Nyayanga, Kenya, the team behind this latest discovery shows that these stone tools were used by early human ancestors to process a wide range of materials and foods, including plants, meat and even bone marrow.

The Oldowan toolkit includes three types of stone tools: hammerstones, cores and flakes. Hammerstones can be used for hitting other rocks to create tools or for pounding other materials. Cores typically have an angular or oval shape, and when struck at an angle with a hammerstone, the core splits off a piece, or flake, that can be used as a cutting or scraping edge or further refined using a hammerstone.

"With these tools you can crush better than an elephant's molar can and cut better than a lion's canine can," Potts said. "Oldowan technology was like suddenly evolving a brand-new set of teeth outside your body, and it opened up a new variety of foods on the African savannah to our ancestors."

Potts and Plummer were first drawn to the Homa Peninsula in Kenya by reports of large numbers of fossilized baboon-like monkeys named Theropithecus oswaldi, which are often found alongside evidence of human ancestors. After many visits to the peninsula, a local man named Peter Onyango working with the team suggested they check out fossils and stone tools eroding from a nearby site that was ultimately named Nyayanga after an adjacent beach.

Beginning in 2015, a series of excavations at Nyayanga returned a trove of 330 artifacts, 1,776 animal bones and the two hominin molars identified as belonging to Paranthropus. The artifacts, Plummer said, were clearly part of the stone-age technological breakthrough that was the Oldowan toolkit.

Compared to the only other stone tools known to have preceded them -- a set of 3.3-million-year-old artifacts unearthed at a site called Lomekwi 3, just west of Lake Turkana in Kenya -- Oldowan tools were a significant upgrade in sophistication. Oldowan tools were systematically produced and often fashioned using what is known as "freehand percussion," meaning the core was held in one hand and then struck with a hammerstone being wielded by the opposing hand at just the right angle to produce a flake -- a technique that requires significant dexterity and skill.

By contrast, most of the artifacts from Lomekwi 3 were created by using large stationary rocks as anvils, with the toolmaker either banging a core against the flat anvil stone to create flakes or by setting the core down on the anvil and striking it with a hammerstone. These more rudimentary modes of fabrication resulted in larger, cruder and more haphazard-looking tools.

Over time, the Oldowan toolkit spread all the way across Africa and even as far as modern-day Georgia and China, and it was not meaningfully replaced or amended until some 1.7 million years ago when the hand-axes of the Acheulean first appeared.

As part of their study, the researchers conducted microscopic analysis of wear patterns on the stone tools to determine how they were used, and they examined any bones seen to exhibit potential cut marks or other kinds of damage that might have come from stone tools.

The site featured at least three individual hippos. Two of these incomplete skeletons included bones that showed signs of butchery. The team found a deep cut mark on one hippo's rib fragment and a series of four short, parallel cuts on the shin bone of another. Plummer said they also found antelope bones that showed evidence of hominins slicing away flesh with stone flakes or of having been crushed by hammerstones to extract marrow.

The analysis of wear patterns on 30 of the stone tools found at the site showed that they had been used to cut, scrape and pound both animals and plants. Because fire would not be harnessed by hominins for another 2 million years or so, these stone toolmakers would have eaten everything raw, perhaps pounding the meat into something like a hippo tartare to make it easier to chew.

Using a combination of dating techniques, including the rate of decay of radioactive elements, reversals of Earth's magnetic field and the presence of certain fossil animals whose timing in the fossil record is well established, the research team was able to date the items recovered from Nyayanga to between 2.58 and 3 million years old.

"This is one of the oldest if not the oldest example of Oldowan technology," Plummer said. "This shows the toolkit was more widely distributed at an earlier date than people realized, and that it was used to process a wide variety of plant and animal tissues. We don't know for sure what the adaptive significance was but the variety of uses suggests it was important to these hominins."

The discovery of teeth from the muscular-jawed Paranthropus alongside these stone tools begs the question of whether it might have been that lineage rather than the Homo genus that was the architect of the earliest Oldowan stone tools, or perhaps even that multiple lineages were making these tools at roughly the same time.

The excavations behind this study offer a snapshot of the world humans' ancestors inhabited and help illustrate the ways that stone technology allowed these early hominins to adapt to different environments and, ultimately, give rise to the human species.

"East Africa wasn't a stable cradle for our species' ancestors," Potts said. "It was more of a boiling cauldron of environmental change, with downpours and droughts and a diverse, ever-changing menu of foods. Oldowan stone tools could have cut and pounded through it all and helped early toolmakers adapt to new places and new opportunities, whether it's a dead hippo or a starchy root."

Read more at Science Daily

Oldest hominins of Olduvai Gorge persisted across changing environments

 Olduvai (now Oldupai) Gorge, known as the Cradle of Humankind, is a UNESCO World Heritage site in Tanzania, made famous by Louis and Mary Leakey. New interdisciplinary field work has led to the discovery of the oldest archaeological site in Oldupai Gorge as reported in Nature Communications, which shows that early human used a wide diversity of habitats amidst environmental changes across a 200,000 year-long period.

Located in the heart of eastern Africa, the Rift System is a prime region for human origins research, boasting extraordinary records of extinct human species and environmental records spanning several million years. For more than a century, archaeologists and human palaeontologists have been exploring the East African Rift outcrops and unearthing hominin fossils in surveys and excavations. However, understanding of the environmental contexts in which these hominins lived has remained elusive due to a dearth of ecological studies in direct association with the cultural remains.

In the new study, published in Nature Communications, researchers from the Max Planck Institute for for the Science of Human History teamed up with lead partners from the University of Calgary, Canada, and the University of Dar es Salaam, Tanzania, to excavate the site of 'Ewass Oldupa' (meaning on 'the way to the Gorge' in the local Maa language, as the site straddles the path that links the canyon's rim with its bottom). The excavations uncovered the oldest Oldowan stone tools ever found at Oldupai Gorge, dating to ~2 million years ago. Excavations in long sequences of stratified sediments and dated volcanic horizons indicated hominin presence at Ewass Oldupai from 2.0 to 1.8 million years ago.

Fossils of mammals (wild cattle and pigs, hippos, panthers, lions, hyena, primates), reptiles and birds, together with a range of multidisciplinary scientific studies, revealed habitat changes over 200,000 years in riverine and lake systems, including fern meadows, woodland mosaics, naturally burned landscapes, lakeside palm groves and dry steppe habitats. The uncovered evidence shows periodic but recurrent land use across a subset of environments, punctuated with times when there is an absence of hominin activity.

Dr. Pastory Bushozi of Dar es Salaam University, Tanzania, notes, "the occupation of varied and unstable environments, including after volcanic activity, is one of the earliest examples of adaptation to major ecological transformations."

Hominin occupation of fluctuating and disturbed environments is unique for this early time period and shows complex behavioural adaptations among early human groups. In the face of changing habitats, early humans did not substantially alter their toolkits, but instead their technology remained stable over time. Indicative of their versatility, typical Oldowan stone tools, consisting of pebble and cobble cores and sharp-edged flakes and polyhedral cobbles, continued to be used even as habitats changed. The implication is that by two million years ago, early humans had the behavioural capacity to continually and consistently exploit a multitude of habitats, using reliable stone toolkits, to likely process plants and butcher animals over the long term.

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DNA from an ancient, unidentified ancestor was passed down to humans living today

 A new analysis of ancient genomes suggests that different branches of the human family tree interbred multiple times, and that some humans carry DNA from an archaic, unknown ancestor. Melissa Hubisz and Amy Williams of Cornell University and Adam Siepel of Cold Spring Harbor Laboratory report these findings in a study published 6th August in PLOS Genetics.

Roughly 50,000 years ago, a group of humans migrated out of Africa and interbred with Neanderthals in Eurasia. But that's not the only time that our ancient human ancestors and their relatives swapped DNA. The sequencing of genomes from Neanderthals and a less well-known ancient group, the Denisovans, has yielded many new insights into these interbreeding events and into the movement of ancient human populations. In the new paper, the researchers developed an algorithm for analyzing genomes that can identify segments of DNA that came from other species, even if that gene flow occurred thousands of years ago and came from an unknown source. They used the algorithm to look at genomes from two Neanderthals, a Denisovan and two African humans. The researchers found evidence that 3 percent of the Neanderthal genome came from ancient humans, and estimate that the interbreeding occurred between 200,000 and 300,000 years ago. Furthermore, 1 percent of the Denisovan genome likely came from an unknown and more distant relative, possibly Homo erectus, and about 15% of these "super-archaic" regions may have been passed down to modern humans who are alive today.

The new findings confirm previously reported cases of gene flow between ancient humans and their relatives, and also point to new instances of interbreeding. Given the number of these events, the researchers say that genetic exchange was likely whenever two groups overlapped in time and space. Their new algorithm solves the challenging problem of identifying tiny remnants of gene flow that occurred hundreds of thousands of years ago, when only a handful of ancient genomes are available. This algorithm may also be useful for studying gene flow in other species where interbreeding occurred, such as in wolves and dogs.

"What I think is exciting about this work is that it demonstrates what you can learn about deep human history by jointly reconstructing the full evolutionary history of a collection of sequences from both modern humans and archaic hominins," said author Adam Siepel. "This new algorithm that Melissa has developed, ARGweaver-D, is able to reach back further in time than any other computational method I've seen. It seems to be especially powerful for detecting ancient introgression."

 From Science Daily

Evidence of Late Pleistocene human colonization of isolated islands beyond Wallace's Line

A new article published in Nature Communications applies stable isotope analysis to a collection of fossil human teeth from the islands of Timor and Alor in Wallacea to study the ecological adaptations of the earliest members of our species to reach this isolated part of the world. Because the Wallacean islands are considered extreme, resource poor settings, archaeologists believed that early seafaring populations would have moved rapidly through this region without establishing permanent communities. Nevertheless, this has so far been difficult to test.

This study, led by scientists from the Department of Archaeology, Max Planck Institute for the Science of Human History (MPI SHH), alongside colleagues from the Australian National University and Universitas Gadjah Mada, used an isotopic methodology that reveals the resources consumed by humans during the period of tooth formation. They demonstrate that the earliest human fossil so far found in the region, dating to around 42,000-39,000 years ago, relied upon coastal resources. Yet, from 20,000 years ago, humans show an increasing reliance on tropical forest environments, away from the island coasts. The results support the idea that one distinguishing characteristic of Homo sapiens is high ecological flexibility, especially when compared to other hominins known from the same region.

Pleistocene hominin adaptations in Southeast Asia

Over the last two decades, archaeological evidence from deserts, high-altitude settings, tropical rainforests, and maritime habitats seem to increasingly suggest that Late Pleistocene humans rapidly adapted to a number of extreme environments. By contrast, our closest hominin relatives, such as Homo erectus and Neanderthals, apparently used various mixtures of forests and grasslands, albeit from as far apart as the Levant, Siberia, and Java. However, this apparent distinction needs testing, especially as finds of another closely related hominin, the Denisovans, have been found on the high-altitude Tibetan Plateau.

As one of the corresponding authors on the new paper, Sue O'Connor of Australian National University says, "The islands beyond Wallace's Line are ideal places to test the adaptive differences between our species and other hominins. These islands were never connected to mainland Southeast Asia during the Pleistocene, and would have ensured that hominins had to make water crossings to reach it." Tropical forest settings like those in Wallacea are often considered barriers to human expansion and are a far cry from the sweeping 'savannahs' with an abundance of medium to large mammals that hominins are believed to have relied on.

Fossils and stone tools show that hominins made it to Wallacean islands at least one million years ago, including the famous 'Hobbit,' or Homo floresiensis, on the island of Flores. When our own species arrived 45,000 years ago (or perhaps earlier), it is thought to have quickly developed the specialized use of marine habitats, as evidenced by one of the world's earliest fish hooks found in the region. Nevertheless, as co-author Ceri Shipton puts it "the extent of this maritime adaptation has remained hotly debated and difficult to test using snapshots based on, often poorly preserved, animal remains."

Stable isotope analysis and Late Pleistocene humans

This new paper uses stable carbon isotopes measured from fossil human teeth to directly reconstruct the long-term diets of past populations. Although this method has been used to study the diets and environments of African hominins for nearly half a century, it has thus far been scarcely applied to the earliest members of our own species expanding within and beyond Africa. Using the principle 'you are what you eat,' researchers analyzed powdered hominin tooth enamel from 26 individuals dated between 42,000 and 1,000 years ago to explore the types of resources they consumed during tooth formation.

The new paper shows that the earliest human fossil available from the region, excavated from the site of Asitau Kuru on Timor, was indeed reliant on maritime resources, suggesting a well-tuned adaptation to the colonization of coastal areas. "This fits with our existing models of rapid human movement through Wallacea on the way to Australia," says co-author Shimona Kealy of the Australian National University.

From around 20,000 years ago, however, human diets seem to have switched inland, towards the supposedly impoverished resources of the island forests. Although some individuals maintained the use of coastal habitats, the majority seemingly began to adapt to the populations of small mammals and tropical forest plants in the region. As co-author Mahirta at Universitas Gadjah Mada puts it, "Coastal resources such as shellfish and reef fish are easy to exploit and available year-round, however growing populations likely forced early island occupants to look inland to other resources."

A species defined by flexibility

This study provides the first direct insights into the adaptations of our own species as it settled in a series of challenging island environments in Wallacea. "Early human populations here, and elsewhere, could not only successfully use the enormous variety of often-extreme Pleistocene environments," suggests Patrick Roberts, lead author of the study and Group Leader at MPI SHH, "they could also specialize in them over substantial periods of time. As a result, even if some local populations did fail, the species as a whole would go on to become tremendously prolific."

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Did ancient supernovae prompt human ancestors to walk upright?

Supernova illustration.

Did ancient supernovae induce proto-humans to walk on two legs, eventually resulting in Homo sapiens with hands free to build cathedrals, design rockets and snap iPhone selfies?

A paper published today in the Journal of Geology makes the case: Supernovae bombarded Earth with cosmic energy starting as many as 8 million years ago, with a peak some 2.6 million years ago, initiating an avalanche of electrons in the lower atmosphere and setting off a chain of events that feasibly ended with bipedal hominins such as Homo habilis, dubbed "handy man."

The authors believe atmospheric ionization probably triggered an enormous upsurge in cloud-to-ground lightning strikes that ignited forest fires around the globe. These infernos could be one reason ancestors of Homo sapiens developed bipedalism -- to adapt in savannas that replaced torched forests in northeast Africa.

"It is thought there was already some tendency for hominins to walk on two legs, even before this event," said lead author Adrian Melott, professor emeritus of physics & astronomy at the University of Kansas. "But they were mainly adapted for climbing around in trees. After this conversion to savanna, they would much more often have to walk from one tree to another across the grassland, and so they become better at walking upright. They could see over the tops of grass and watch for predators. It's thought this conversion to savanna contributed to bipedalism as it became more and more dominant in human ancestors."

Based on a "telltale" layer of iron-60 deposits lining the world's sea beds, astronomers have high confidence supernovae exploded in Earth's immediate cosmic neighborhood -- between 100 and only 50 parsecs (163 light years) away -- during the transition from the Pliocene Epoch to the Ice Age.

"We calculated the ionization of the atmosphere from cosmic rays which would come from a supernova about as far away as the iron-60 deposits indicate," Melott said. "It appears that this was the closest one in a much longer series. We contend it would increase the ionization of the lower atmosphere by 50-fold. Usually, you don't get lower-atmosphere ionization because cosmic rays don't penetrate that far, but the more energetic ones from supernovae come right down to the surface -- so there would be a lot of electrons being knocked out of the atmosphere."

According to Melott and co-author Brian Thomas of Washburn University, ionization in the lower atmosphere meant an abundance of electrons would form more pathways for lightning strikes.

"The bottom mile or so of atmosphere gets affected in ways it normally never does," Melott said. "When high-energy cosmic rays hit atoms and molecules in the atmosphere, they knock electrons out of them -- so these electrons are running around loose instead of bound to atoms. Ordinarily, in the lightning process, there's a buildup of voltage between clouds or the clouds and the ground -- but current can't flow because not enough electrons are around to carry it. So, it has to build up high voltage before electrons start moving. Once they're moving, electrons knock more electrons out of more atoms, and it builds to a lightning bolt. But with this ionization, that process can get started a lot more easily, so there would be a lot more lightning bolts."

The KU researcher said the probability that this lightning spike touched off a worldwide upsurge in wildfires is supported by the discovery of carbon deposits found in soils that correspond with the timing of the cosmic-ray bombardment.

"The observation is that there's a lot more charcoal and soot in the world starting a few million years ago," Melott said. "It's all over the place, and nobody has any explanation for why it would have happened all over the world in different climate zones. This could be an explanation. That increase in fires is thought to have stimulated the transition from woodland to savanna in a lot of places -- where you had forests, now you had mostly open grassland with shrubby things here and there. That's thought to be related to human evolution in northeast Africa. Specifically, in the Great Rift Valley where you get all these hominin fossils."

Melott said no such event is likely to occur again anytime soon. The nearest star capable of exploding into a supernova in the next million years is Betelgeuse, some 200 parsecs (652 light years) from Earth.

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First hominins on the Tibetan Plateau were Denisovans

The Xiahe mandible, only represented by its right half, was found in 1980 in Baishiya Karst Cave.

Denisovans -- an extinct sister group of Neandertals -- were discovered in 2010, when a research team led by Svante Pääbo from the Max Planck Institute for Evolutionary Anthropology (MPI-EVA) sequenced the genome of a fossil finger bone found at Denisova Cave in Russia and showed that it belonged to a hominin group that was genetically distinct from Neandertals. "Traces of Denisovan DNA are found in present-day Asian, Australian and Melanesian populations, suggesting that these ancient hominins may have once been widespread," says Jean-Jacques Hublin, director of the Department of Human Evolution at the MPI-EVA. "Yet so far the only fossils representing this ancient hominin group were identified at Denisova Cave."

Mandible from Baishiya Karst Cave

In their new study, the researchers now describe a hominin lower mandible that was found on the Tibetan Plateau in Baishiya Karst Cave in Xiahe, China. The fossil was originally discovered in 1980 by a local monk who donated it to the 6th Gung-Thang Living Buddha who then passed it on to Lanzhou University. Since 2010, researchers Fahu Chen and Dongju Zhang from Lanzhou University have been studying the area of the discovery and the cave site from where the mandible originated. In 2016, they initiated a collaboration with the Department of Human Evolution at the MPI-EVA and have since been jointly analysing the fossil.

While the researchers could not find any traces of DNA preserved in this fossil, they managed to extract proteins from one of the molars, which they then analysed applying ancient protein analysis. "The ancient proteins in the mandible are highly degraded and clearly distinguishable from modern proteins that may contaminate a sample," says Frido Welker of the MPI-EVA and the University of Copenhagen. "Our protein analysis shows that the Xiahe mandible belonged to a hominin population that was closely related to the Denisovans from Denisova Cave."

Primitive shape and large molars

The researchers found the mandible to be well-preserved. Its robust primitive shape and the very large molars still attached to it suggest that this mandible once belonged to a Middle Pleistocene hominin sharing anatomical features with Neandertals and specimens from the Denisova Cave. Attached to the mandible was a heavy carbonate crust, and by applying U-series dating to the crust the researchers found that the Xiahe mandible is at least 160,000 years old. Chuan-Chou Shen from the Department of Geosciences at National Taiwan University, who conducted the dating, says: "This minimum age equals that of the oldest specimens from the Denisova Cave."

"The Xiahe mandible likely represents the earliest hominin fossil on the Tibetan Plateau," says Fahu Chen, director of the Institute of Tibetan Research, CAS. These people had already adapted to living in this high-altitude low-oxygen environment long before Homo sapiens even arrived in the region. Previous genetic studies found present-day Himalayan populations to carry the EPAS1 allele in their genome, passed on to them by Denisovans, which helps them to adapt to their specific environment.

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The history of humanity in your face

These are skulls of hominins over the last 4.4 million years.

The face you see in the mirror is the result of millions of years of evolution and reflects the most distinctive features that we use to identify and recognize each other, molded by our need to eat, breath, see, and communicate.

But how did the modern human face evolve to look the way it does? Eight of the top experts on the evolution of the human face, including Arizona State University's William Kimbel, collaborated on an article published this week in the journal Nature Ecology & Evolution to tell this four-million-year story. Kimbel is the director of the Institute of Human Origins and Virginia M. Ullman Professor of Natural History and the Environment in the School of Human Evolution and Social Change.

After our ancestors stood on two legs and began to walk upright, at least 4.5 million years ago, the skeletal framework of a bipedal creature was pretty well formed. Limbs and digits became longer or shorter, but the functional architecture of bipedal locomotion had developed.

But the skull and teeth provide a rich library of changes that we can track over time, describing the history of evolution of our species. Prime factors in the changing structure of the face include a growing brain and adaptations to respiratory and energy demands, but most importantly, changes in the jaw, teeth, and face responded to shifts in diet and feeding behavior. We are, or we evolved to be, what we eat -- literally!

Diet has played a large role in explaining evolutionary changes in facial shape. The earliest human ancestors ate tough plant foods that required large jaw muscles and cheek teeth to break down, and their faces were correspondingly broad and deep, with massive muscle attachment areas.

As the environment changed to drier, less wooded conditions, especially in the last two million years, early Homo species began to routinely use tools to break down foods or cut meat. The jaws and teeth changed to meet a less demanding food source, and the face became more delicate, with a flatter countenance.

Changes in the human face may not be due only to purely mechanical factors. The human face, after all, plays an important role in social interaction, emotion, and communication. Some of these changes may be driven, in part, by social context. Our ancestors were challenged by the environment and increasingly impacted by culture and social factors. Over time, the ability to form diverse facial expressions likely enhanced nonverbal communication.

Large, protruding brow ridges are typical of some extinct species of our own genus, Homo, like Homo erectus and the Neanderthals. What function did these structures play in adaptive changes in the face? The African great apes also have strong brow ridges, which researchers suggest help to communicate dominance or aggression. It is probably safe to conclude that similar social functions influenced the facial form of our ancestors and extinct relatives. Along with large, sharp canine teeth, large brow ridges were lost along the evolutionary road to our own species, perhaps as we evolved to become less aggressive and more cooperative in social contexts.

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New species of early human found in the Philippines

Professor Philip Piper from the ANU School of Archaeology and Anthropology inspects the cast of a hominin third metatarsal discovered in 2007. The bone is from a new species of hominin.

An international team of researchers have uncovered the remains of a new species of human in the Philippines, proving the region played a key role in hominin evolutionary history. The new species, Homo luzonensis is named after Luzon Island, where the more than 50,000 year old fossils were found during excavations at Callao Cave.

Co-author and a lead member of the team, Professor Philip Piper from The Australian National University (ANU) says the findings represent a major breakthrough in our understanding of human evolution across Southeast Asia.

The researchers uncovered the remains of at least two adults and one juvenile within the same archaeological deposits.

"The fossil remains included adult finger and toe bones, as well as teeth. We also recovered a child's femur. There are some really interesting features -- for example, the teeth are really small," Professor Piper said.

"The size of the teeth generally, though not always, reflect the overall body-size of a mammal, so we think Homo luzonensis was probably relatively small. Exactly how small we don't know yet. We would need to find some skeletal elements from which we could measure body-size more precisely" Professor Piper said.

"It's quite incredible, the extremities, that is the hand and feet bones are remarkably Australopithecine-like. The Australopithecines last walked the earth in Africa about 2 million years ago and are considered to be the ancestors of the Homo group, which includes modern humans.

"So, the question is whether some of these features evolved as adaptations to island life, or whether they are anatomical traits passed down to Homo luzonensis from their ancestors over the preceding 2 million years."

While there are still plenty of questions around the origins of Homo luzonensis, and their longevity on the island of Luzon, recent excavations near Callao Cave produced evidence of a butchered rhinoceros and stone tools dating to around 700,000 years ago.

"No hominin fossils were recovered, but this does provide a timeframe for a hominin presence on Luzon. Whether it was Homo luzonensis butchering and eating the rhinoceros remains to be seen," Professor Piper said.

"It makes the whole region really significant. The Philippines is made up of a group of large islands that have been separated long enough to have potentially facilitated archipelago speciation. There is no reason why archaeological research in the Philippines couldn't discover several species of hominin. It's probably just a matter of time."

Homo luzonensis shares some unique skeletal features with the famous Homo floresiensis or 'the hobbit', discovered on the island of Flores to the south east of the Philippine archipelago.

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Changes in rat size reveal habitat of 'Hobbit' hominin

This is a graphic image of the Liang Bua rat species used in the study.

A study of rat body sizes shifting over time gives a glimpse into the habitat of the mysterious hominin Homo floresiensis -- nicknamed the "Hobbit" due to its diminutive stature.

The Journal of Human Evolution is publishing the study, based on an analysis of thousands of rodent bones, mainly fore- and hind-limbs, from an Indonesian cave where H. floresiensis was discovered in 2003. The results indicate that the local habitat was mostly open grasslands more than 100,000 years ago, but began shifting rapidly to a more closed environment 60,000 years ago.

"Our paper is the first that we know of to use the leg bones of rats in this way to interpret ecological change through time, and it provides new evidence for the local environment during the time of Homo Floresiensis," says Elizabeth Grace Veatch, a PhD candidate at Emory University and a first author of the study.

H. floresiensis stood only about 3 feet 6 inches tall and was known to have lived about 190,000 to 50,000 years ago on the oceanic island of Flores in eastern Indonesia. The tiny hominin shared the island with animals that could have come from the pages of a Tolkien novel, including giant Komodo dragons, six-foot-tall storks, vultures with a six-foot wingspan, and pygmy Stegodons -- herbivores that looked like small elephants with swooping, oversized tusks.

It was the rats, however, that most interested Veatch.

Murids, as the rat family is known, are more taxonomically diverse than any other mammal group and are found in nearly every part of the world. "They exhibit an incredible range of behaviors occupying many different ecological niches," Veatch says. "And because small mammals are typically sensitive to ecological shifts, they can tell you a lot about what's going on in an environment."

The study was based on remains recovered from the limestone cave known as Liang Bua, where partial skeletons of H. floresiensis have been found, along with stone tools and the remains of animals -- most of them rats. In fact, out of the 275,000 animal bones identified in the cave so far, 80 percent of them are from rodents.

Veatch came to Emory to work with paleoanthropologist Jessica Thompson, a leading expert in using taphonomy -- the study of what happens to bones after an organism dies -- to learn more about the evolution of the human diet. Although Thompson has now moved to Yale University, she continues to mentor Veatch in her graduate studies at Emory.

Veatch became part of the Liang Bua project while doing an internship with the Human Origins Program of the Smithsonian Institution's National Museum of Natural History. Her mentor there was paleoanthropologist Matthew Tocheri (now with Lakehead University in Ontario) who shares first-authorship of the current paper with Veatch.

"Matthew asked me if I wanted to analyze some rat bones and I said, 'Sure,'" Veatch recalls. "I had no idea what I was getting into."

The study encompassed about 10,000 of the Liang Bua rat bones. The remains spanned five species with distinct sizes, from the mouse-sized Rattus hainaldi up to the housecat-sized Papagomys armandvillei -- commonly known as the Flores giant rat. After categorizing the bones, the researchers could then directly link them to both species and environmental types.

While rats can adjust to new environments, the morphologies of different species tend to be adaptive to their preferred environment. For example, the habitat of the medium-sized Komodomys rintjanus, included in the study, is primarily open grasslands intermittent with patches of forest. In contrast, the tiny R. hainaldi and the giant P. armandvillei both prefer more closed or semi-closed forested habitats.

Tracking the relative abundances of the different rat species over time indicated that the local ecology was mostly open grassland 100,000 years ago, transitioning to a more-closed, forested habitat around 60,000 years ago. That is around the same time that skeletal elements belonging to Homo floresiensis, the pygmy Stegodon, giant storks, vulture and Komodo dragons disappear from Liang Bua.

"The evidence suggests that Homo floresiensis may have preferred more open habitats where they may have been a part of this scavenging guild of Stegodons, storks and vultures," Veatch says. "We think that when the habitat changed, becoming more forested, Homo floresiensis probably left the Liang Bua area, tracking these animals to more open habitats elsewhere on the island."

Many more mysteries remain regarding H. floresiensis, Veatch says, and the Liang Bua rat bones may help solve some of them.

One key question is whether H. floresiensis hunted small game.

"Our early ancestors adapted to consuming large amounts of big game through hunting or scavenging -- or both," Veatch says. "Big game undoubtedly became a critical food source, resulting in numerous social and physiological adaptations, including social cooperation and brain expansion. It's much less known, however, what role small-game hunting may have played in our early evolution -- if any at all."

Liang Bua, she says, offers an ideal opportunity to study what a small-brained hominin, like H. floresiensis, might hunt if it had both sources of big game, like the Stegodon, and small game, like the giant Flores rat and other rat species.

Veatch is conducting field studies at the Liang Bua site, including running experiments to determine how difficult it would be to capture wild Flores rats. She is also doing research at the Pusat Penelitian Arkeologi Nasional (ARKENAS) Museum in the Indonesian capital of Jakarta where many of the bones from the cave site are now stored. She is analyzing a large sample of the bones to determine if any have cut marks -- indicating butchering with tools -- or pitted marks that would indicate they were digested by owls or other raptors that may have deposited them in the cave.

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From Stone Age chips to microchips: How tiny tools may have made us human

The iconic, tear-drop shaped hand axe, which filled a human palm, required a large toolkit to produce (left), in contrast to a toolkit for tiny flakes.

Anthropologists have long made the case that tool-making is one of the key behaviors that separated our human ancestors from other primates. A new paper, however, argues that it was not tool-making that set hominins apart -- it was the miniaturization of tools.

Just as tiny transistors transformed telecommunications a few decades ago, and scientists are now challenged to make them even smaller, our Stone Age ancestors felt the urge to make tiny tools. "It's a need that we've been perennially faced with and driven by," says Justin Pargeter, an anthropologist at Emory University and lead author of the paper. "Miniaturization is the thing that we do."

The journal Evolutionary Anthropology is publishing the paper -- the first comprehensive overview of prehistoric tool miniaturization. It proposes that miniaturization is a central tendency in hominin technologies going back at least 2.6 million years.

"When other apes used stone tools, they chose to go big and stayed in the forests where they evolved," says co-author John Shea, professor of anthropology at Stony Brook University. "Hominins chose to go small, went everywhere, and transformed otherwise hostile habitats to suit our changing needs."

The paper reviews how stone flakes less than an inch in length -- used for piercing, cutting and scraping -- pop up in the archeological record at sites on every continent, going back to some of the earliest known stone tool assemblages. These small stone flakes, Pargeter says, were like the disposable razor blades or paperclips of today -- pervasive, easy to make and easily replaced.

He identifies three inflection points for miniaturization in hominin evolution. The first spike occurred around two million years ago, driven by our ancestors' increasing dependence on stone flakes in place of nails and teeth for cutting, slicing and piercing tasks. A second spike occurred sometime after 100,000 years ago with the development of high-speed weaponry, such as the bow and arrow, which required light-weight stone inserts. A third spike in miniaturization occurred about 17,000 years ago. The last Ice Age was ending, forcing some humans to adapt to rapid climate change, rising sea levels and increased population densities. These changes increased the need to conserve resources, including the rocks and minerals needed to make tools.

A native of South Africa, Pargeter co-directs field work in that country along its rugged and remote Indian Ocean coastline and nearby inland mountains. He is also a post-doctoral fellow in Emory University's Center for Mind, Brain and Culture and the Department of Anthropology's Paleolithic Technology Laboratory. The lab members actually make stone tools to better understand how our ancestors learned these skills, and how that process shaped our evolution. The lab's director, Dietrich Stout, focuses on hand axes, dating back more than 500,000 years. These larger tools are considered a turning point in human biological and cognitive evolution, due to the complexity involved in making them.

Pargeter's work on tiny tools adds another facet to the investigation of human evolution. "He's exploring what may have led to the compulsion to produce these tiny instruments -- essentially the relationship between the tools and the human body, brain and the probable uses of the tools," Stout says.

When looking for a PhD thesis topic, Pargeter first focused on collections of larger implements, considered typical of the Stone Age tool kit. He pored over artifacts from a South African site called Boomplaas that were being held in storage at the Iziko Museum in Cape Town. As he rummaged through a bag labelled as waste -- containing small flakes thought to be left over from making larger tools -- something caught his eye. A sliver of crystal quartz looked like it had been shaped using a highly technical method called pressure flaking.

"It was diminutive, about the size of a small raisin, and weighed less than half a penny," he recalls. "You could literally blow it off your finger."

Pargeter examined the flake under a magnifying glass. He noticed it had a distinctive, stair-step fracture on its tip that previous experimental research showed to be associated with damage caused in hunting.

"It suddenly occurred to me that archeologists may have missed a major component of our stone tool record," Pargeter says. "In our desire to make 'big' discoveries we may have overlooked tiny, but important, details. A whole technology could lay hidden behind our methods, relegated to bags considered waste material."

So how to interpret the use of a tool so tiny that you could easily blow it off your finger?

Pargeter began thinking of this question in terms of the age of the flake -- about 17,000 years -- and the environment at the time. The last Ice Age was ending and massive melting of ice at the poles caused the global sea-level to rise. In parts of South Africa, the rising oceans swallowed an area the size of Ireland. As the coastal marshes and grasslands disappeared -- along with much of the game and aquatic life -- the hunter-gatherers living there fled inland to sites like Boomplaas, currently located about 80 kilometers inland. The mountains around Boomplaas provided permanent springs and other dependable freshwater sources.

The climate, however, was less predictable, with sudden shifts in temperature and rainfall. Vegetation was shifting dramatically, temperatures were rising and large mammals were increasingly scarce. Archaeology from Boomplaas shows that people ate small game like hares and tortoises. These small animals would have been easy to catch, but they provided limited nutritional packages.

"These are low-reward food sources, indicating a foraging stress signal," Pargeter says. "Boomplaas might have even served as a type of refugee camp, with groups of hunter-gatherers moving away from the coast, trying to survive in marginal environments as resources rapidly depleted and climate change ratcheted up."

Arrow points a little less than an inch across were already in the archaeological literature, but the Boomplaas crystal quartz flake was half that size. In order to bring down an animal, Pargeter hypothesized, the Boomplaas flake would need poison on its tip -- derived either from plants or insects -- and a high-speed delivery system, such as a bow and arrow.

Pargeter used his own extensive knowledge of prehistoric tool-making and archaeology to hypothesize that the tiny flake could have been hafted, using a plant-based resin, onto a link shaft, also likely made of a plant-based material, such as a reed. That link shaft, about the length of a finger, would in turn fit onto a light arrow shaft.

"The link shaft goes into the animal, sacrificing the small blade, but the arrow shaft pops out so you can retain this more costly component," he says. "Our ancestors were masters of aerodynamics and acted like engineers, rather than what we think of as 'cave people.' They built redundancy into their technological systems, allowing them to easily repair their tools and to reduce the impact of errors."

Our ancestors were also connoisseurs of the type of fine-grained rocks needed for tool-making.

Supplies of such vital toolmaking raw materials, however, were likely diminished as the rising oceans consumed land and people became more crowded together, driving them to more carefully conserve what they could find on the landscape.

As paleoanthropologists are faced with more than three million years of hominin "stuff," one of the perennial questions they keep seeking to answer is, what makes us humans unique? "We've typically said that tool use makes us human, but that's kind of buckled under," Pargeter says, as evidence of tool use by other animals accumulates.

Macaques, for example, use rocks to smash apart oysters. Chimpanzees use rocks as hammers and anvils to crack nuts and they modify sticks to dig and fish for termites. These tools, however, are large. "The hands of other primates are not evolved for repeated fine manipulation in high-force tasks," Pargeter says. "We've evolved a unique precision grip that ratchets up our ability for miniaturized technology."

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Humans colonized diverse environments in Southeast Asia and Oceania during the Pleistocene

Cagayan, Northern Luzon, the Philippines -- Southeast Asia offers a particularly exciting region in regard of early hominin movements across the supposed "Movius Line" a boundary previously argued to separate populations. Records from the region can be linked to a variety of hominins throughout the Pleistocene, including Homo erectus, Homo floresiensis (or "the Hobbit"), and Homo sapiens.

Investigations into what it means to be human have often focused on attempts to uncover the earliest material traces of 'art', 'language', or technological 'complexity'. More recently, however, scholars have begun to argue that more attention should be paid to the ecological uniqueness of our species. A new study, published in Archaeological Research in Asia, reviews the palaeoecological information associated with hominin dispersals into Southeast Asia and Oceania throughout the Pleistocene (1.25 Ma to 12 ka). Our species' ability to specialize in the exploitation of diverse and 'extreme' settings in this part of the world stands in stark contrast to the ecological adaptations of other hominin taxa, and reaffirms the utility of exploring the environmental adaptations of Homo sapiens as an avenue for understanding what it means to be human.

The paper, published by scientists from the Max Planck Institute for the Science of Human History focuses on hominin movements across the supposed 'Movius Line' a boundary previously argued to separate populations with different cultural and cognitive capacities. While such divisions and assumptions are now clearly outdated, the authors argue that focus on this part of the world may, instead, be used to study the different patterns of colonization of diverse tropical and maritime habitats by different members of our ancestral line. As Noel Amano, co-author on the study states, 'analysis of biogeochemical records, animal assemblages, and fossil plant records associated with hominin arrival can be used to reconstruct the degree to which novel or specialized adaptations were required at a given place and time'.

Southeast Asia offers a particularly exciting region in this regard as such records can be linked to a variety of hominins throughout the Pleistocene, including Homo erectus, Homo floresiensis (or 'the Hobbit'), and Homo sapiens. As Patrick Roberts, lead author of the study states the accumulated evidence shows, 'While earlier members of our genus appear to have followed riverine and lacustrine corridors, Homo sapiens specialized in adaptations to tropical rainforests, faunally depauperate island settings, montane environments, and deep-water marine habitats.' The authors hope that, in future, the growth of new methods and records for determining past hominin ecologies will enable similar comparisons to be undertaken in different parts of the world, further testing the unique capacities of our species during its global expansion.

From Science Daily

The whole of Africa was the cradle of humankind

Members of Ain Hanech team excavating at Ain Boucherit.

A team of scientists led by Mohamed Sahnouni, archaeologist at the Centro Nacional de Investigación sobre la Evolución Humana (CENIEH), has just published a paper in the journal Science which breaks with the paradigm that the cradle of Humankind lies in East Africa, based on the archaeological remains found at sites in the region of Ain Hanech (Algeria), the oldest currently known in the north of Africa.

For a long time, East Africa has been considered the place of origin of the earliest hominins and lithic technology, because up to now, very little was known about the first hominin occupation and activities in the north of the continent. Two decades of field and laboratory research directed by Dr. Sahnouni have shown that ancestral hominins actually made stone tools in North Africa that are near contemporary with the earliest known stone tools in East Africa dated to 2.6 million years.

These are stone artifacts and animal bones bearing marks of cutting by stone tools, with an estimated chronology of 2.4 and 1.9 million years, respectively, found at two levels at the sites of Ain Boucherit (within the Ain Hanech study area), which were dated using Paleomagnetism, Electron Spin Resonance (ESR), and the Biochronology of large mammals excavated together with the archaeological materials.

Fossils of animals such as pigs, horses and elephants, from very ancient sites, have been used by the paleontologist Jan van der Made, of the Museo Nacional de Ciencias Naturales in Madrid, to corroborate the ages yielded by Paleomagnetism, obtained by the CENIEH geochronologist Josep Parés, and ESR, found by Mathieu Duval, of Griffith University.

Oldowan technology

The artifacts of Ain Boucherit were manufactured of locally available limestone and flint and include faces worked into choppers, polyhedra and subspheroids, as well as sharp-edged cutting tools used to process animal carcasses. These artifacts are typical of the Oldowan stone technology known from 2.6-1.9 million-year-old sites in East Africa, although those from Ain Boucherit show subtle variations.

"The lithic industry of Ain Boucherit, which is technologically similar to that of Gona and Olduvai, shows that our ancestors ventured into all corners of Africa, not just East Africa. The evidence from Algeria changes the earlier view that East Africa was the cradle of Humankind. Actually, the whole of Africa was the cradle of humankind," states Sahnouni, leader of the Ain Hanech project.

Not mere scavengers

Ain Boucherit is one of the few archaeological sites in Africa which has provided evidence of bones with associated marks of cutting and percussion in situ with stone tools, which shows unmistakably that these ancestral hominins exploited meat and marrow from animals of all sizes and skeletal parts, which implied skinning, evisceration and defleshing of upper and intermediate extremities.

Isabel Cáceres, taphonomist at the IPHES, has commented that "the effective use of sharp-edged tools at Ain Boucherit suggests that our ancestors were not mere scavengers. It is not clear at this moment whether they hunted, but the evidence clearly shows that they were successfully competing with carnivores and enjoyed first access to animal carcasses."

The tool-makers

At this moment, the most important question is who made the stone tools discovered in Algeria. Hominin remains have still not been found in North Africa which are contemporary with the earliest stone artifacts. As a matter of fact, nor have any hominins yet been documented in direct association with the first stone tools known from East Africa.

Nevertheless, a recent discovery in Ethiopia has shown the presence of early Homo dated to 2.8 million years, most likely the best candidate also for the materials from East and North Africa.

Scientists thought for a long time that the hominins and their material culture originated in the Great Rift Valley in East Africa. Surprisingly, the earliest known hominin, dated to 7.0 million years, and the 3.3 million years Australopithecus bahrelghazali, have been discovered in Chad, in the Sahara, 3000 km from the rift valleys in the east of Africa.

As Sileshi Semaw, scientist at the CENIEH and a co-author of this paper, explains that the hominins contemporary with Lucy (3.2 million years), were probably roamed over the Sahara, and their descendants might have been responsible for leaving these archaeological puzzles now discovered in Algeria, that are near contemporaries of those of East Africa.

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Evolution: South Africa's hominin record is a fair-weather friend

Field photograph of massive flowstone layers from one of the South African hominin caves, with red cave sediments underneath.

New research from an international team of scientists led by University of Cape Town isotope geochemist Dr Robyn Pickering is the first to provide a timeline for fossils from the caves within the Cradle of Humankind. It also sheds light on the climate conditions of our earliest ancestors in the area.

Published online in the journal Nature on 21 November 2018, the work corrects assumptions that the region's fossil-rich caves could never be related to each other. In fact, the research suggests fossils from Cradle caves date to just six specific time periods.

"Unlike previous dating work, which often focused on one cave, sometimes even just one chamber of the cave, we are providing direct ages for eight caves and a model to explain the age of all the fossils from the entire region," says Dr Robyn Pickering.

"Now we can link together the findings from separate caves and create a better picture of evolutionary history in southern Africa."

The Cradle of Humankind is a World Heritage Site made up of complex fossil-bearing caves. It's the world's richest early hominin site and home to nearly 40% of all known human ancestor fossils, including the famous Australopithecus africanus skull nicknamed Mrs Ples.

Using uranium-lead dating, researchers analysed 28 flowstone layers that were found sandwiched between fossil-rich sediment in eight caves across the Cradle. The results revealed that the fossils in these caves date to six narrow time-windows between 3.2 and 1.3 million years ago.

"The flowstones are the key," says Pickering. "We know they can only grow in caves during wet times, when there is more rain outside the cave. By dating the flowstones, we are picking out these times of increased rainfall. We therefore know that during the times in between, when the caves were open, the climate was drier and more like what we currently experience."

This means the early hominins living in the Cradle experienced big changes in local climate, from wetter to drier conditions, at least six times between 3 and 1 million years ago. However, only the drier times are preserved in the caves, skewing the record of early human evolution.

Up until now, the lack of dating methods for Cradle fossils made it difficult for scientists to understand the relationship between East and South Africa hominin species. Moreover, the South African record has often been considered undateable compared to East Africa where volcanic ash layers allow for high resolution dating.

Professor Andy Herries, a co-author in the study at La Trobe University in Australia, notes that "while the South African record was the first to show Africa as the origin point for humans, the complexity of the caves and difficultly dating them has meant that the South African record has remained difficult to interpret."

"In this study we show that the flowstones in the caves can act almost like the volcanic layers of East Africa, forming in different caves at the same time, allowing us to directly relate their sequences and fossils into a regional sequence," he says.

Dr Pickering began dating the Cradle caves back in 2005 as part of her PhD research. This new publication is the result of 13 years of work and brings together a team of 10 scientists from South Africa, Australia and the US. The results return the Cradle to the forefront and open new opportunities for scientists to answer complex questions about human history in the region.

"Robyn and her team have made a major contribution to our understanding of human evolution," says leading palaeoanthropologist Professor Bernard Wood, of the Center for the Advanced Study of Human Paleobiology at the George Washington University in the USA, who is not an author on the study.

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