New geological datings place the first European hominids in the south of the Iberian Peninsula 1.3 million years ago

One of the most important controversies about human evolution and expansion is when and by what route the first hominids arrived in Europe from the African continent. Now, geological dating techniques at the Orce sites (Baza basin, Granada, Spain) place the human remains found in this area as the oldest in Europe, at approximately 1.3 million years old. These results reinforce the hypothesis that humans arrived in Europe through the south of the Iberian Peninsula, through the Strait of Gibraltar, instead of returning to the Mediterranean via the Asian route. The study, led by Lluís Gibert, researcher and lecturer at the University of Barcelona's Faculty of Earth Sciences, has involved the participation of researchers from the Berkeley Geochronology Centre and Murray State University (United States).

Analysis of a new sampling area

The new dating has been based on the analysis of the paleomagnetism of an area of the Orce region, which has never been sampled before and which has been protected from the erosion that this basin has suffered over the years. This technique is a relative dating method based on the study of the inversion of the magnetic poles of the planet due to the internal dynamics of the Earth. These changes do not have a specific periodicity, but they are recorded in the minerals and make it possible to establish time periods from the different magnetic events.

These new data are very precise thanks to the long sedimentary sequence that outcrops in Orce. "The uniqueness of these sites is that they are stratified and within a very long sedimentary sequence, more than eighty metres long. Normally, the sites are found in caves or within very short stratigraphic sequences, which do not allow you to develop long palaeomagnetic sequences in which you can find different magnetic reversals," says Lluís Gibert.

The researchers have been able to identify a magnetic polarity sequence "with five magnetic events that allow them to place the three Orce sites with human presence between the Olduvai and Jaramillo subchron, that is, between 1.77 and 1.07 million years ago (Ma)," says the researcher. Subsequently, they have applied a statistical age model to accurately refine the chronology of the different stratigraphic levels with a margin of error of only 70,000 years. The result of this innovative methodology is that the oldest site with human presence in Europe would be Venta Micena with an age of 1.32 Ma, followed by Barranco León, with an age of 1.28 and finally Fuente Nueva 3, with an age of 1.23 Ma. "With these data, the other major site on the peninsula, the Sima del Elefante in Atapuerca, would be relegated to second place, far behind Orce, between 0.2 and 0.4 Ma more modern," adds the researcher.

Fauna underpins the antiquity of the site

To complete the dating, the study has also analyzed the fauna found at the different sites in Orce, as this is different depending on the period, and compared it with that found at other Early Pleistocene sites in other parts of Europe.

In this sense, the paper presents a detailed analysis of the micromammals and large mammals from all the Orce sites, carried out by the expert Robert Martin, based on the palaeontological collections stored at the Museum of the Catalan Institute of Palaeontology Miguel Crusafont (IPS) in Sabadell. "The results indicate that the small and large fauna of Orce is more primitive than, for example, that of the Sima del Elefante, where the evidence shows that the rodent Allophaiomys lavocati is more evolved than the Allophaiomys recovered from the Orce sites," Gibert explains.Another relevant indicator of the age of the Orce sites is the absence of the ancestors of the pigs. "These animals are considered to be Asian immigrants and have not been found in any European site between 1 and 1.5 Ma, while they have been found in the Sima del Elefante, supporting that the Orce fauna is older," explains the researcher.

Evidence pointing to passage through Gibraltar

This new dating would be added, according to the researcher, to other evidence that would tip the balance in favour of the colonization of Europe through the Strait of Gibraltar, rather than the alternative route: the return to the Mediterranean via Asia, such as "the existence of a lithic industry with similarities to that found in the north of the African continent and also the presence of remains of African fauna in the south of the peninsula, such as those of Hippopotamus, found in the sites of Orce, and those of Theropithecus oswaldi, an African primate similar to a baboon, found in the Victoria cave, a site near Cartagena (Murcia), non-existent anywhere else in Europe."

"We also defend the hypothesis -- adds the researcher -- that they arrived from Gibraltar because no older evidence has been found at any other site along the alternative route."

These new data are very precise thanks to the long sedimentary sequence that outcrops in Orce.

Similarity with hominids from the island of Flores

With these results, the researchers point to a "diachronism" between the oldest occupation of Asia, measuring 1.8 Ma, and the oldest occupation of Europe, which would be 1.3 Ma ago, so that African hominids would have arrived in southwestern Europe more than 0.5 Ma after leaving Africa for the first time about 2 Ma ago. "These differences in human expansion can be explained by the fact that Europe is isolated from Asia and Africa by biogeographical barriers that are difficult to overcome, both to the east (Bosphorus Strait, Dardanelles, Sea of Marmara) and to the west (Strait of Gibraltar). Humanity arrived in Europe when it had the necessary technology to cross maritime barriers, as happened before a million years ago on the island of Flores (Indonesia)," says Gibert. In this sense, the researcher adds that the Gibraltar route currently requires crossing up to fourteen kilometres of sea route, but "perhaps in the past this distance was shorter at certain times due to the high tectonic activity in this region and the fluctuations in sea level that favoured migrations."

"As cited in the paper -- he adds -- , we have identified other migrations of African fauna through Gibraltar at earlier times, 6.2 and 5.5 Ma ago when the Strait of Gibraltar was very narrow."

Human remains in Orce

A total of five human remains were found at the Orce sites since excavations began in 1982 by the palaeoanthropologist Josep Gibert. Firstly, two fragments of humerus bitten by hyenas were found at Venta Micena, as well as parts of a cranial fragment consisting of two parietals and an occipital, associated with an abundant Early Pleistocene fauna. The human provenance of these remains generated great controversy for years, although independent palaeoproteomic studies by the universities of Granada and San Francisco identified human proteins in the remains.

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'Genomic time machine' reveals secrets of our DNA

The human genome, an intricate tapestry of genetic information for life, has proven to be a treasure trove of strange features. Among them are segments of DNA that can "jump around" and move within the genome, known as "transposable elements" (TEs).

As they change their position within the genome, TEs can potentially cause mutations and alter the cell's genetic profile, but also are master orchestrators of our genome's organization and expression.

For example, TEs contribute to regulatory elements, transcription factor binding sites, and the creation of chimeric transcripts -- genetic sequences created when segments from two different genes or parts of the genome join together to form a new, hybrid RNA molecule.

Matching their functional importance, TEs have been recognized to account for half of the human DNA.

However, as they move and age, TEs pick up changes that mask their original form.

Over time, TEs "degenerate" and become less recognizable, making it difficult for scientists to identify and track them in our genetic blueprint.

In a new study, researchers in the group of Didier Trono at EPFL have found a way to improve the detection of TEs in the human genome by using reconstructed ancestral genomes from various species, which allowed them to identify previously undetectable degenerate TEs in the human genome.

The study is published in Cell Genomics.

The scientists used a database of reconstructed ancestral genomes from different kinds of species, like a genomic "time machine." By comparing the human genome with the reconstructed ancestral genomes, they could identify TEs in the latter that, over millions of years, have become degenerate (worn out) in humans.

This comparison allowed them to detect ("annotate") TEs that might have been missed in previous studies that used data only from the human genome.

Using this approach, the scientists uncovered a larger number of TEs than previously known, adding significantly to the share of our DNA that is contributed by TEs.

Furthermore, they could demonstrate that these newly unearthed TE sequences played all the same regulatory roles as their more recent, already identified relatives.

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Focus on function helps identify the changes that made us human

Humans split away from our closest animal relatives, chimpanzees, and formed our own branch on the evolutionary tree about seven million years ago. In the time since -- brief, from an evolutionary perspective -- our ancestors evolved the traits that make us human, including a much bigger brain than chimpanzees and bodies that are better suited to walking on two feet. These physical differences are underpinned by subtle changes at the level of our DNA. However, it can be hard to tell which of the many small genetic differences between us and chimps have been significant to our evolution.

New research from Whitehead Institute Member Jonathan Weissman; University of California, San Francisco Assistant Professor Alex Pollen; Weissman lab postdoc Richard She; Pollen lab graduate student Tyler Fair; and colleagues uses cutting edge tools developed in the Weissman lab to narrow in on the key differences in how humans and chimps rely on certain genes. Their findings, published in the journal Cell on June 20th, may provide unique clues into how humans and chimps have evolved, including how humans became able to grow comparatively large brains.

Studying function rather than genetic code

Only a handful of genes are fundamentally different between humans and chimps; the rest of the two species' genes are typically nearly identical. Differences between the species often come down to when and how cells use those nearly identical genes. However, only some of the many differences in gene use between the two species underlie big changes in physical traits. The researchers developed an approach to narrow in on these impactful differences.

Their approach, using stem cells derived from human and chimp skin samples, relies on a tool called CRISPR interference (CRISPRi) that Weissman's lab developed. CRISPRi uses a modified version of the CRISPR/Cas9 gene editing system to effectively turn off individual genes. The researchers used CRISPRi to turn off each gene one at a time in a group of human stem cells and a group of chimp stem cells. Then they looked to see whether or not the cells multiplied at their normal rate. If the cells stopped multiplying as quickly or stopped altogether, then the gene that had been turned off was considered essential: a gene that the cells need to be active-producing a protein product-in order to thrive. The researchers looked for instances in which a gene was essential in one species but not the other as a way of exploring if and how there were fundamental differences in the basic ways that human and chimp cells function.

By looking for differences in how cells function with particular genes disabled, rather than looking at differences in the DNA sequence or expression of genes, the approach ignores differences that do not appear to impact cells. If a difference in gene use between species has a large, measurable effect at the level of the cell, this likely reflects a meaningful difference between the species at a larger physical scale, and so the genes identified in this way are likely to be relevant to the distinguishing features that have emerged over human and chimp evolution.

"The problem with looking at expression changes or changes in DNA sequences is that there are many of them and their functional importance is unclear," says Weissman, who is also a professor of biology at the Massachusetts Institute of Technology and an Investigator with the Howard Hughes Medical Institute. "This approach looks at changes in how genes interact to perform key biological processes, and what we see by doing that is that, even on the short timescale of human evolution, there has been fundamental rewiring of cells."

After the CRISPRi experiments were completed, She compiled a list of the genes that appeared to be essential in one species but not the other. Then he looked for patterns. Many of the 75 genes identified by the experiments clustered together in the same pathways, meaning the clusters were involved in the same biological processes. This is what the researchers hoped to see. Individual small changes in gene use may not have much of an effect, but when those changes accumulate in the same biological pathway or process, collectively they can cause a substantive change in the species. When the researchers' approach identified genes that cluster in the same processes, this suggested to them that their approach had worked and that the genes were likely involved in human and chimp evolution.

"Isolating the genetic changes that made us human has been compared to searching for needles in a haystack because there are millions of genetic differences, and most are likely to have negligible effects on traits," Pollen says. "However, we know that there are lots of small effect mutations that in aggregate may account for many species differences. This new approach allows us to study these aggregate effects, enabling us to weigh the impact of the haystack on cellular functions."

Researchers think bigger brains may rely on genes regulating how quickly cells divide

One cluster on the list stood out to the researchers: a group of genes essential to chimps, but not to humans, that help to control the cell cycle, which regulates when and how cells decide to divide. Cell cycle regulation has long been hypothesized to play a role in the evolution of humans' large brains. The hypothesis goes like this: Neural progenitors are the cells that will become neurons and other brain cells. Before becoming mature brain cells, neural progenitors divide multiple times to make more of themselves. The more divisions that the neural progenitors undergo, the more cells the brain will ultimately contain -- and so, the bigger it will be. Researchers think that something changed during human evolution to allow neural progenitors to spend less time in a non-dividing phase of the cell cycle and transition more quickly towards division. This simple difference would lead to additional divisions, each of which could essentially double the final number of brain cells.

Consistent with the popular hypothesis that human neural progenitors may undergo more divisions, resulting in a larger brain, the researchers found that several genes that help cells to transition more quickly through the cell cycle are essential in chimp neural progenitor cells but not in human cells. When chimp neural progenitor cells lose these genes, they linger in a non-dividing phase, but when human cells lose them, they keep cycling and dividing. These findings suggest that human neural progenitors may be better able to withstand stresses -- such as the loss of cell cycle genes -- that would limit the number of divisions the cells undergo, enabling humans to produce enough cells to build a larger brain.

"This hypothesis has been around for a long time, and I think our study is among the first to show that there is in fact a species difference in how the cell cycle is regulated in neural progenitors," She says. "We had no idea going in which genes our approach would highlight, and it was really exciting when we saw that one of our strongest findings matched and expanded on this existing hypothesis."

More subjects lead to more robust results

Research comparing chimps to humans often uses samples from only one or two individuals from each species, but this study used samples from six humans and six chimps. By making sure that the patterns they observed were consistent across multiple individuals of each species, the researchers could avoid mistaking the naturally occurring genetic variation between individuals as representative of the whole species. This allowed them to be confident that the differences they identified were truly differences between species.

The researchers also compared their findings for chimps and humans to orangutans, which split from the other species earlier in our shared evolutionary history. This allowed them to figure out where on the evolutionary tree a change in gene use most likely occurred. If a gene is essential in both chimps and orangutans, then it was likely essential in the shared ancestor of all three species; it's more likely for a particular difference to have evolved once, in a common ancestor, than to have evolved independently multiple times. If the same gene is no longer essential in humans, then its role most likely shifted after humans split from chimps. Using this system, the researchers showed that the changes in cell cycle regulation occurred during human evolution, consistent with the proposal that they contributed to the expansion of the brain in humans.

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Homo sapiens likely arose from multiple closely related populations

In testing the genetic material of current populations in Africa and comparing against existing fossil evidence of early Homo sapiens populations there, researchers have uncovered a new model of human evolution -- overturning previous beliefs that a single African population gave rise to all humans. The new research was published today, May 17, in the journal Nature.

Although it is widely understood that Homo sapiens originated in Africa, uncertainty surrounds how branches of human evolution diverged and how people migrated across the continent, said Brenna Henn, professor of anthropology and the Genome Center at UC Davis, corresponding author of the research.

"This uncertainty is due to limited fossil and ancient genomic data, and to the fact that the fossil record does not always align with expectations from models built using modern DNA," she said. "This new research changes the origin of species."

Research co-led by Henn and Simon Gravel of McGill University tested a range of competing models of evolution and migration across Africa proposed in the paleoanthropological and genetics literature, incorporating population genome data from southern, eastern and western Africa.

The authors included newly sequenced genomes from 44 modern Nama individuals from southern Africa, an Indigenous population known to carry exceptional levels of genetic diversity compared to other modern groups. Researchers generated genetic data by collecting saliva samples from modern individuals going about their everyday business in their villages between 2012 and 2015.

The model suggests the earliest population split among early humans that is detectable in contemporary populations occurred 120,000 to 135,000 years ago, after two or more weakly genetically differentiated Homo populations had been mixing for hundreds of thousands of years. After the population split, people still migrated between the stem populations, creating a weakly structured stem. This offers a better explanation of genetic variation among individual humans and human groups than do previous models, the authors suggest.

"We are presenting something that people had never even tested before," Henn said of the research. "This moves anthropological science significantly forward."

"Previous more complicated models proposed contributions from archaic hominins, but this model indicates otherwise," said co-author Tim Weaver, UC Davis professor of anthropology. He has expertise in what early human fossils looked like and provided comparative research for the study.

The authors predict that, according to this model, 1-4% of genetic differentiation among contemporary human populations can be attributed to variation in the stem populations. This model may have important consequences for the interpretation of the fossil record. Owing to migration between the branches, these multiple lineages were probably morphologically similar, which means morphologically divergent hominid fossils (such as Homo naledi) are unlikely to represent branches that contributed to the evolution of Homo sapiens, the authors said.

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Human ancestors preferred mosaic landscapes and high ecosystem diversity

A new study published in the journal Science by an international team finds that early human species adapted to mosaic landscapes and diverse food resources, which would have increased our ancestor's resilience to past shifts in climate.

Our genus Homo evolved over the past 3 million years -- a period of increasing warm/cold climate fluctuations. How early human species have adapted to the intensification of climate extremes, ice ages, and large-scale shifts in landscapes and vegetation remains elusive. Did our ancestors adjust to local environmental changes over time, or did they seek out more stable environments with diverse food resources? Was our human evolution influenced more by temporal changes in climate, or by the spatial character of the environment?

To test these fundamental hypotheses on human evolution and adaptation quantitively, the research team used a compilation of more than three thousand well-dated human fossil specimens and archeological sites, representing six different human species, in combination with realistic climate and vegetation model simulations, covering the past 3 million years. The scientists focused their analysis on biomes -- geographic regions which are characterized by similar climates, plants, and animal communities (e.g., savannah, rainforest, or tundra).

"For the archeological and anthropological sites and corresponding ages, we extracted the local biome types from our climate-driven vegetation model. This revealed which biomes were favored by the extinct hominin species H. ergaster, H. habilis, H. erectus, H. heidelbergensis, and H. neanderthalensis andbyour direct ancestors -- H. sapiens.," said Elke Zeller, Ph.D. student from the IBS Center for Climate Physics at Pusan National University, South Korea, and lead author of the study.

According to their analysis, the scientists found that earlier African groups preferred to live in open environments, such as grassland and dry shrubland. Migrating into Eurasia around 1.8 million years ago, hominins, such as H. erectus and later H. heidelbergensis and H. neanderthalensis developed higher tolerances to other biomes over time, including temperate and boreal forests. "To survive as forest-dwellers, these groups developed more advanced stone tools and likely also social skills," said Prof. Pasquale Raia, from the Università di Napoli Federico II, Italy, co-author of the study. Eventually, H. sapiens emerged around 200,000 years ago in Africa, quickly becoming the master of all trades. Mobile, flexible, and competitive, our direct ancestors, unlike any other species before, survived in harsh environments such as deserts and tundra.

When further looking into the preferred landscape characteristics, the scientists found a significant clustering of early human occupation sites in regions with increased biome diversity. "What that means is that our human ancestors had a liking for mosaic landscapes, with a great variety of plant and animal resources in close proximity," said Prof. Axel Timmermann, co-author of the study and Director of the IBS Center for Climate Physics in South Korea. The results indicate that ecosystem diversity played a key role in human evolution.

The authors demonstrated this preference for mosaic landscapes for the first time on continental scales and propose a new Diversity Selection Hypothesis: Homo species, and H. sapiens, in particular, were uniquely equipped to exploit heterogeneous biomes. "Our analysis shows the crucial importance of landscape and plant diversity as a selective element for humans and as a potential driver for socio-cultural developments" adds Elke Zeller. Elucidating how vegetation shifts have shaped human sustenance, the new Science study provides an unprecedented view into human prehistory and survival strategies.

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Human evolution wasn't just the sheet music, but how it was played

A team of Duke researchers has identified a group of human DNA sequences driving changes in brain development, digestion and immunity that seem to have evolved rapidly after our family line split from that of the chimpanzees, but before we split with the Neanderthals.

Our brains are bigger, and are guts are shorter than our ape peers.

"A lot of the traits that we think of as uniquely human, and human-specific, probably appear during that time period," in the 7.5 million years since the split with the common ancestor we share with the chimpanzee, said Craig Lowe, Ph.D., an assistant professor of molecular genetics and microbiology in the Duke School of Medicine.

Specifically, the DNA sequences in question, which the researchers have dubbed Human Ancestor Quickly Evolved Regions (HAQERS), pronounced like hackers, regulate genes. They are the switches that tell nearby genes when to turn on and off. The findings appear Nov.23 in the journal Cell.

The rapid evolution of these regions of the genome seems to have served as a fine-tuning of regulatory control, Lowe said. More switches were added to the human operating system as sequences developed into regulatory regions, and they were more finely tuned to adapt to environmental or developmental cues. By and large, those changes were advantageous to our species.

"They seem especially specific in causing genes to turn on, we think just in certain cell types at certain times of development, or even genes that turn on when the environment changes in some way," Lowe said.

A lot of this genomic innovation was found in brain development and the GI tract. "We see lots of regulatory elements that are turning on in these tissues," Lowe said. "These are the tissues where humans are refining which genes are expressed and at what level."

Today, our brains are larger than other apes, and our guts are shorter. "People have hypothesized that those two are even linked, because they are two really expensive metabolic tissues to have around," Lowe said. "I think what we're seeing is that there wasn't really one mutation that gave you a large brain and one mutation that really struck the gut, it was probably many of these small changes over time."

To produce the new findings, Lowe's lab collaborated with Duke colleagues Tim Reddy, an associate professor of biostatistics and bioinformatics, and Debra Silver, an associate professor of molecular genetics and microbiology to tap their expertise. Reddy's lab is capable of looking at millions of genetic switches at once and Silver is watching switches in action in developing mouse brains.

"Our contribution was, if we could bring both of those technologies together, then we could look at hundreds of switches in this sort of complex developing tissue, which you can't really get from a cell line," Lowe said.

"We wanted to identify switches that were totally new in humans," Lowe said. Computationally, they were able to infer what the human-chimp ancestor's DNA would have been like, as well as the extinct Neanderthal and Denisovan lineages. The researchers were able to compare the genome sequences of these other post-chimpanzee relatives thanks to databases created from the pioneering work of 2022 Nobel laureate Svante Pääbo.

"So, we know the Neanderthal sequence, but let's test that Neanderthal sequence and see if it can really turn on genes or not," which they did dozens of times.

"And we showed that, whoa, this really is a switch that turns on and off genes," Lowe said. "It was really fun to see that new gene regulation came from totally new switches, rather than just sort of rewiring switches that already existed."

Along with the positive traits that HAQERs gave humans, they can also be implicated in some diseases.

Most of us have remarkably similar HAQER sequences, but there are some variances, "and we were able to show that those variants tend to correlate with certain diseases," Lowe said, namely hypertension, neuroblastoma, unipolar depression, bipolar depression and schizophrenia. The mechanisms of action aren't known yet, and more research will have to be done in these areas, Lowe said.

"Maybe human-specific diseases or human-specific susceptibilities to these diseases are going to be preferentially mapped back to these new genetic switches that only exist in humans," Lowe said.

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Ancient genomes reveal hidden history of human adaptation

The use of ancient DNA, including samples of human remains around 45,000 years old, has shed light on a previously unknown aspect of human evolution.

Dr Yassine Souilmi, Group Leader at the University of Adelaide's Australian Centre for Ancient DNA, co-led the new study published in Nature Ecology and Evolution.

"It was widely believed the genetics of our human ancestors didn't change due to environmental pressures as much as other animals, due to our enhanced communication skills and ability to make and use tools," Dr Souilmi said.

"However, by comparing modern genomes with ancient DNA, we discovered more than 50 cases of an initially rare beneficial genetic variant becoming prevalent across all members of ancient human groups.

"In contrast to many other species, evidence for this type of adaptive genetic change has been inconsistent in humans. This discovery consequently challenges the prevailing view of human adaptation, and gives us a new and exciting insight into how humans have adapted to the novel environmental pressures they encountered as we spread across the planet."

Co-lead author Dr Ray Tobler -- an Adjunct Fellow at the University of Adelaide and a DECRA fellow at the Australian National University -- said examining ancient DNA has been critical in unlocking the secrets of human evolution.

"We believed historical mixing events between human groups might have hidden signs of genetic changes in modern human genomes," Dr Tobler said.

"We examined DNA from more than 1,000 ancient genomes, the oldest which was around 45,000 years old, to see if certain types of genetic adaptation had been more common in our history than studies of modern genomes had suggested."

Professor Christian Huber, a senior author of the research paper, is an Adjunct Fellow at the University of Adelaide and an Assistant Professor at Penn State University.

"The use of ancient genomes was crucial because they preceded major historical mixing events that have radically reshaped modern European genetic ancestry," Professor Huber said.

"This allowed the recovery of historical signs of adaptation that are invisible to standard analysis of modern genomes."

Established in 2005, the Australian Centre for Ancient DNA is a world leader in the research and development of advanced ancient DNA approaches for evolutionary, environmental and conservation applications.

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Key phases of human evolution coincide with flickers in eastern Africa's climate

Three distinct phases of climate variability in eastern Africa coincided with shifts in hominin evolution and dispersal over the last 620,000 years, an analysis of environmental proxies from a lake sediment record has revealed. The project explores the youngest chapter in human evolution by analysing lacustrine sediments in close vicinity to paleo-anthropological key sites in eastern Africa using scientific deep drilling. The research endeavour included more than 22 researchers from 19 institutions in 6 countries, and was led by Dr Verena Foerster at the University of Cologne's Institute of Geography Education. The article 'Pleistocene climate variability in eastern Africa influenced hominin evolution' has now appeared in Nature Geoscience.

Despite more than half a century of hominin fossil discoveries in eastern Africa, the regional environmental context of the evolution and dispersal of modern humans and their ancestors is not well established. Particularly for the Pleistocene (or Ice Age) between 2,580,000 to 11,700 years ago, there are no continuous high-resolution paleo-environmental records available for the African continent.

The research team extracted two continuous 280-metre sediment cores from the Chew Bahir Basin in southern Ethiopia, an area where early humans lived and developed during the Pleistocene. Chew Bahir is very remotely situated in a deep tectonic basement in close vicinity to the Turkana area and the Omo-Kibish, key paleo-anthropological and archaeological sites. The cores yielded the most complete record for such a long period ever extracted in the area, revealing how different climates influenced the biological and cultural transformation of humans inhabiting the region.

An interdisciplinary team including geoscientists, sedimentologists, micro-paleontologists, geologists, geographers, geochemists, archaeologists, chronologists, and climate modellers worked towards recovering the two continuous sediment cores, from which so-called proxies (like microfossils or elemental variations) were used to glean data to reconstruct the region's climate history. Archaeologists, evolutionary biologists, and evolutionary anthropologists then identified phases of climatic stress as well as more favourable conditions and interpreted how these factors changed human habitats, influencing human biological and cultural evolution as well as their dispersal.

Specifically, the scientists found that various anatomically diverse hominin groups inhabited the area during a phase of long-lasting and relatively stable humid conditions from approximately 620,000 to 275,000 years BP (Before Present). However, a series of shorter abrupt and extreme arid pulses interrupted this long generally stable and wet phase. Most likely, this resulted in a fragmentation of habitats, shifts in population dynamics and even the extinctions of local populations. As a result, small, reproductively and culturally isolated populations then had to adapt to dramatically transformed local environments, likely stimulating the appearance of the many geographically and anatomically distinct hominin groups and the separation of our modern human ancestors from archaic groups.

A phase with significant climate swings resulting in regularly transformed habitats in the area from approximately 275,000 to 60,000 years BP repeatedly resulted in environmental shifts from lush vegetation with deep fresh water lakes to highly arid landscapes with the extensive lakes reduced to small saline puddles. In this phase, the population groups gradually transitioned from Acheulean technologies (oval hand axes made of stone and primarily associated with Homo ergaster/erectus) to more sophisticated Middle Stone Age technologies. This crucial phase also encompasses the emergence of Homo sapiens in eastern Africa as well as key human social, technological, and cultural innovations that could have buffered early Homo sapiens from the impacts of severe environmental changes. 'These innovations, such as more varied toolkits and long-distance transport, would have equipped modern humans with an unprecedented adaptability to the repeated expansions and contractions of habitats,' said Dr Foerster, the paper's lead author.

The phase from approximately 60,000 to 10,000 years BP saw the most extreme environmental fluctuations, but also the most arid phase of the entire record, which could have acted as a motor for continuous indigenous cultural change. The scientists believe that the brief alignment of humid pulses in eastern Africa with wet phases in north-eastern Africa and the Mediterranean was key to opening favourable migration routes out of Africa on a roughly north-south axis along the East African Rift System (EARS) and into the Levant, facilitating the global dispersal of Homo sapiens.

'In view of current threats to the human habitat from climate change and the overuse of natural resources through human activity, understanding how the relationship between climate and human evolution has become more relevant than ever,' Foerster concluded.

This research is part of the Hominin Sites and Paleolakes Drilling Project (HSPDP). In order to evaluate the impact that different timescales and magnitudes of climatic shifts have had on the living conditions of early humans, the project has cored five lake archives of climate change during the last 3.5 million years. All five sites in Kenya and Ethiopia are located in close vicinity to paleoanthropological key sites covering various steps in human evolution, with the site in southern Ethiopia exploring the youngest chapter.

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The gene to which we owe our big brain

ARHGAP11B -- this complex name is given to a gene that is unique to humans and plays an essential role in the development of the neocortex. The neocortex is the part of the brain to which we owe our high mental abilities. A team of researchers from the German Primate Center (DPZ) -- Leibniz Institute for Primate Research in Göttingen, the Max Planck Institute for Molecular Cell Biology and Genetics (MPI-CBG) in Dresden, and the Hector Institute for Translational Brain Research (HITBR) in Mannheim has investigated the importance of ARHGAP11B in neocortex development during human evolution.

To do this, the team introduced for the first time a gene that exists only in humans into laboratory-grown brain organoids from our closest living relatives, chimpanzees. In the chimpanzee brain organoid, the ARHGAP11B gene led to an increase in brain stem cells relevant to brain growth and an increase in those neurons that play a critical role in the extraordinary mental abilities of humans. If, on the other hand, the ARHGAP11B gene was switched off in human brain organoids, the quantity of these brain stem cells fell to the level of a chimpanzee. Thus, the research team was able to show that the ARGHAP11B gene played a crucial role in the evolution of the brain from our ancestors to modern humans.

Animal studies on great apes have long been banned in Europe for ethical reasons. For the question pursued here, so-called organoids, i.e. three-dimensional cell structures a few millimeters in size that are grown in the laboratory, are an alternative to animal experiments. These organoids can be produced from pluripotent stem cells, which then differentiate into specific cell types, such as nerve cells. In this way, the research team was able to produce both chimpanzee brain organoids and human brain organoids. "These brain organoids allowed us to investigate a central question concerning ARHGAP11B," says Wieland Huttner of the MPI-CBG, one of the three lead authors of the study.

"In a previous study we were able to show that ARHGAP11B can enlarge a primate brain. However, it was previously unclear whether ARHGAP11B had a major or minor role in the evolutionary enlargement of the human neocortex," says Wieland Huttner. To clarify this, the ARGHAP11B gene was first inserted into brain ventricle-like structures of chimpanzee organoids. Would the ARGHAP11B gene lead to the proliferation of those brain stem cells in the chimpanzee brain that are necessary for the enlargement of the neocortex? "Our study shows that the gene in chimpanzee organoids causes an increase in relevant brain stem cells and an increase in those neurons that play a crucial role in the extraordinary mental abilities of humans," said Michael Heide, the study's lead author, who is head of the Junior Research Group Brain Development and Evolution at the DPZ and employee at the MPI-CBG. When the ARGHAP11B gene was knocked out in human brain organoids or the function of the ARHGAP11B protein was inhibited, the amount of these brain stem cells decreased to the level of a chimpanzee. "We were thus able to show that ARHGAP11B plays a crucial role in neocortex development during human evolution," says Michael Heide. Julia Ladewig of HITBR, the third of the lead authors, adds: "Given this important role of ARHGAP11B, it is furthermore conceivable that certain maldevelopments of the neocortex may be caused by mutations in this gene."

From Science Daily

Sahelanthropus, the oldest representative of humanity, was indeed bipedal...but that's not all!

The acquisition of bipedalism is considered to be a decisive step in human evolution. Nevertheless, there is no consensus on its modalities and age, notably due to the lack of fossil remains. A research team, involving researchers from the CNRS, the University of Poitiers1 and their Chadian partners, examined three limb bones from the oldest human representative currently identified, Sahelanthropus tchadensis. Published in Nature on August 24, 2022, this study reinforces the idea of bipedalism being acquired very early in our history, at a time still associated with the ability to move on four limbs in trees.

At 7 million years old, Sahelanthropus tchadensis is considered the oldest representative species of humanity. Its description dates back to 2001 when the Franco-Chadian Paleoanthropological Mission (MPFT) discovered the remains of several individuals at Toros-Menalla in the Djurab Desert (Chad), including a very well-preserved cranium. This cranium, and in particular the orientation and anterior position of the occipital foramen where the vertebral column is inserted, indicates a mode of locomotion on two legs, suggesting that it was capable of bipedalism2.

In addition to the cranium, nicknamed Toumaï, and fragments of jaws and teeth that have already been published, the locality of Toros-Menalla 266 (TM 266) yielded two ulnae (forearm bone) and a femur (thigh bone). These bones were also attributed to Sahelanthropus because no other large primate was found at the site; however, it is impossible to know if they belong to the same individual as the cranium. Palaeontologists from the University of Poitiers, the CNRS, the University of N'Djamena and the National Centre of Research for Development (CNRD, Chad) published their complete analysis in Nature on August 24, 2022.

The femur and ulnae were subjected to a battery of measurements and analyses, concerning both their external morphology, and their internal structures using microtomography imaging: biometric measurements, geometric morphometrics, biomechanical indicators, etc. These data were compared to those of a relatively large sample of extant and fossil apes: chimpanzees, gorillas, orangutans, Miocene apes, and members of the human group (Orrorin, Ardipithecus, australopithecines, ancient Homo, Homo sapiens).

The structure of the femur indicates that Sahelanthropus was usually bipedal on the ground, but probably also in trees. According to results from the ulnae, this bipedalism coexisted in arboreal environments with a form of quadrupedalism, that is arboreal clambering enabled by firm hand grips, clearly differing from that of gorillas and chimpanzees who lean on the back of their phalanges.

The conclusions of this study, including the identification of habitual bipedalism, are based on the observation and comparison of more than twenty characteristics of the femur and ulnae. They are, by far, the most parsimonious interpretation of the combination of these traits. All these data reinforce the concept of a very early bipedal locomotion in human history, even if at this stage other modes of locomotion were also practiced.

Read more at Science Daily

Study of ancient skulls sheds light on human interbreeding with Neanderthals

Research has established that there are traces of Neandertal DNA in the genome of modern humans. Now an exploratory study that assessed the facial structure of prehistoric skulls is offering new insights, and supports the hypothesis that much of this interbreeding took place in the Near East -- the region ranging from North Africa to Iraq.

"Ancient DNA caused a revolution in how we think about human evolution," says Steven Churchill, co-author of the study and a professor of evolutionary anthropology at Duke University. "We often think of evolution as branches on a tree, and researchers have spent a lot of time trying to trace back the path that led to us, Homo sapiens. But we're now beginning to understand that it isn't a tree -- it's more like a series of streams that converge and diverge at multiple points."

"Our work here gives us a deeper understanding of where those streams came together," says Ann Ross, corresponding author of the study and a professor of biological sciences at North Carolina State University.

"The picture is really complicated," Churchill says. "We know there was interbreeding. Modern Asian populations seem to have more Neandertal DNA than modern European populations, which is weird -- because Neandertals lived in what is now Europe. That has suggested that Neandertals interbred with what are now modern humans as our prehistoric ancestors left Africa, but before spreading to Asia. Our goal with this study was to see what additional light we could shed on this by assessing the facial structure of prehistoric humans and Neandertals."

"By evaluating facial morphology, we can trace how populations moved and interacted over time," Ross explains. "And the evidence shows us that the Near East was an important crossroads, both geographically and in the context of human evolution."

For this study, the researchers collected data on craniofacial morphology from the published literature. This ultimately resulted in a data set including 13 Neandertals, 233 prehistoric Homo sapiens, and 83 modern humans.

The researchers focused on standard craniofacial measurements, which are reproducible, and used those measurements to assess the size and shape of key facial structures. This then allowed the researchers to do an in-depth analysis to determine whether a given human population was likely to have interbred with Neandertal populations, as well as the extent of that likely interbreeding.

"Neandertals had big faces," Churchill says. "But size alone doesn't establish any genetic link between a human population and Neandertal populations. Our work here involved a more robust analysis of the facial structures."

The researchers also accounted for environmental variables that are associated with changes in human facial characteristics, to determine the likelihood that connections they established between Neandertal and human populations were the result of interbreeding rather than other factors.

"We found that the facial characteristics we focused on were not strongly influenced by climate, which made it easier to identify likely genetic influences," Ross says. "We also found that facial shape was a more useful variable for tracking the influence of Neandertal interbreeding in human populations over time. Neandertals were just bigger than humans. Over time, the size of human faces became smaller, generations after they had bred with Neandertals. But the actual shape of some facial features retained evidence of interbreeding with Neandertals."

"This was an exploratory study," Churchill says. "And, honestly, I wasn't sure this approach would actually work -- we have a relatively small sample size, and we didn't have as much data on facial structures as we would have liked. But, ultimately, the results we got are really compelling.

Read more at Science Daily

What oxytocin can tell us about the evolution of human prosociality

Modern humans are characterized by their prosociality, a broad term that encompasses intraspecies empathy, social tolerance, cooperation and altruism. These facets of social cognition have been associated with variations in the oxytocin and vasotocin genes (OT and VT) and their receptors (OTR and VTR).To shed light on the genetic basis of this behaviour, scientists from the University of Barcelona (UB) and Rockefeller University carried out a new study comparing the available genomic sequences of these genes between modern humans, non-human primate species (e.g., chimpanzees, bonobos, and macaques) and, for the first time, archaic humans, using all the available genomes of Neanderthals and Denisovans.

In the study, published in the journal Comprehensive Psychoneuroendocrinology, the researchers identified several sites in which modern humans differed from both archaic humans and non-human primates, and others where both modern and archaic humans differed from non-human primates.

"We used an interdisciplinary approach to understand the evolution of hominid prosociality through the lens of the oxytocin and vasotocin receptors, where we combined evidence from modern and archaic genomics, population genetics, transcriptomics, and behavioural and neuroscientific studies, among other methods. These results can shed light on the genetics underlying possible sociality differences identified between modern humans and archaic humans, as well as the similarities between the modern human and bonobo social behaviour," said first author Constantina Theofanopoulou. This research is part of her doctoral thesis carried out under the co-supervision of Cedric Boeckx, ICREA researcher at the Institute of Complex Systems at the UB (UBICS) and Erich D. Jarvis, professor at Rockefeller University.

Variants unique to modern humans in more than 70% of the population

Considering the evidence on modern human prosociality and on the involvement of the oxytocin and vasotocin genes in social behaviours, the researchers hypothesized that the evolution of these genes might elucidate the genetic basis of the evolution of hominin prosociality. With this aim in mind, the study explored the differences between modern humans, archaic humans and non-human primates in polymorphic heterozygous sites in the human genome -- locations where at least two alternative sequences are found in a population. "Past studies that compared the entire modern human genome with the Neanderthal or the chimpanzee genomes have focused on changes that are fixed or nearly fixed in modern humans. This has led to them identifying sites where, for example, all Neanderthals had Adenine (one of the four nucleotides that with guanine, cytosine and thymine form the DNA) and nearly all modern humans (say, 98%) have Guanine. In this study, we searched for differences on locations where, by definition, not all modern humans share the same nucleotide, namely on polymorphic sites, where for example, 70% of the modern human population has Adenine and 30% Cytosine," adds Theofanopoulou.

The researchers identified five sites in the oxytocin and vasotocin receptors where modern humans are unique in one of their two (or more) variants compared to archaic humans and non-human primates, and which are at the same time found in more than 70% of the modern human population. Next, they conducted functional and frequency analyses to establish whether the variants are relevant. They performed a range of analyses on the five sites and found that some of the variants are highly functional, indicating that they have an effect on the molecular function of the proteins activated by these genes.

The researchers also found that these sites are encountered in genome regions that are active in the brain, particularly in the cingulate gyrus, a brain region involved in social cognition-relevant pathways. Moreover, all these sites have been associated in other studies with a plethora of social behaviours or social deficits, such as autism, attention deficit hyperactivity disorder (ADHD), aggression, and so on.

These findings may help to explain some of the social differences between modern humans and what we presume to know about the social behaviours of Neanderthals and Denisovans. "For example, they might be relevant to the smaller social groups attributed to Neanderthals and Denisovans or to the decreased modern human androgenization. They might also be relevant to a different social structure, i.e., Neanderthals have been linked to a polygynous social structure and a higher level of male-male competition than most contemporary modern human populations," says Constantina Theofanopoulou.

Variants present only in modern and archaic humans

The study also found two sites on the oxytocin receptor under a positive selection in modern and archaic humans: that is to say, modern and archaic humans showed a variant that was not present in any other non-human primate. This means that these sites are found in very high percentages in the modern human population (in this case, more than 85%). These same sites have also been associated with a great many social behaviours or deficits, and one of them was predicted to be a highly functional site in their regulation analyses. "The sites that are unique in both us and archaic humans versus non-human primates can elucidate the genetic underpinnings of the progressive social tolerance needed for the intensive cultural transmission of technological innovations (e.g., fire use) in the evolution of humankind, as well as for the reduced aggression indicated by several markers in early hominid evolution, such as the reduction of male canine size and the accelerated demographic success," adds Theofanopoulou.

Convergent sites with bonobos

Lastly, the researchers found three sites where modern humans and bonobos, a primate species that shows convergence of prosocial behaviours with humans, have the same nucleotide. "The convergent sites in modern humans and bonobos could be insightful for understanding the posited similarities in prosociality, social tolerance and cooperation between us and bonobos, and the differences of both compared to chimpanzees. For example, bonobos outperform chimpanzees on tasks relevant to social causality or theory of mind and are more attentive to the face and eyes, suggestive of higher empathic sensitivity," notes the researcher.

All the sites identified in this study have also been independently associated with disorders that include social deficits, such as autism spectrum disorders (ASD). "Understanding developmental disorders through evolutionary lenses can aid into us achieving what we call an evo-devo (evolutionary and developmental biology) understanding of these disorders. If indeed "ontogeny recapitulates phylogeny," then deciphering our evolutionary trajectory may shed light to new genetic spots for clinical research that might, in turn, lead to earlier disorder diagnosis," highlights Constantina Theofanopoulou.

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

Disbelief in human evolution linked to greater prejudice and racism

A disbelief in human evolution was associated with higher levels of prejudice, racist attitudes and support of discriminatory behavior against Blacks, immigrants and the LGBTQ community in the U.S., according to University of Massachusetts Amherst research published in the Journal of Personality and Social Psychology.

Similarly, across the globe -- in 19 Eastern European countries, 25 Muslim countries and in Israel -- low belief in evolution was linked to higher biases within a person's group, prejudicial attitudes toward people in different groups and less support for conflict resolution.

The findings supported the hypothesis of lead author Stylianos Syropoulos, a Ph.D. candidate in the War and Peace Labof senior author Bernhard Leidner, associate professor of social psychology. They collaborated with co-first author Uri Lifshin at Reichman University in Israel and co-authors Jeff Greenberg and Dylan Horner at the University of Arizona in Tucson. The researchers theorized that belief in evolution would tend to increase people's identification with all humanity, due to the common ancestry, and would lead to less prejudicial attitudes.

"People who perceive themselves as more similar to animals are also people who tend to have more pro-social or positive attitudes toward outgroup members or people from stigmatized and marginalized backgrounds," Syropoulos explains. "In this investigation, we were interested in examining whether belief in evolution would also act in a similar way, because it would reinforce this belief that we are more similar to animals."

In eight studies involving different areas of the world, the researchers analyzed data from the American General Social Survey (GSS), the Pew Research Center and three online crowdsourced samples. In testing their hypothesis about the associations of different levels of belief in evolution, they accounted for education, political ideology, religiosity, cultural identity and scientific knowledge.

"We found the same results each time, which is basically that believing in evolution relates to less prejudice, regardless of the group you're in, and controlling for all of these alternative explanations," Syropoulos says.

For example, religious beliefs, like political ideology, were measured separately from a belief or disbelief in evolution, the researchers note. "Regardless of whether one considers religion an important part of their life, belief in evolution relates to less prejudice independently from belief, or lack thereof, in God or any particular religion," Syropoulos says.

Leidner adds, "This whole effect and pattern seems to be present in all major political systems. It's very much a human phenomenon, no matter where you are in the world."

The researchers note that Darwin's 19th century theory of evolution has been cited to perpetrate racism, prejudice and homophobia, in part through the phrase, "survival of the fittest," used to describe the process of natural selection.

"There have been theoretical accounts that predict the opposite of what we found, so it was exciting for us to show that this actually is not the case, that the opposite is true and that belief in evolution seems to have pretty positive effects," Leidner says.

The U.S.-based study involved data from 1993, 1994, 2000, 2006, 2008, 2010, 2012, 2014, 2016 and 2018 -- the years the GSS surveyed Americans about their beliefs in evolution, as well as measures of attitudes toward immigrants, Blacks, affirmative action, LGBTQ people and other social matters.

The data analysis showed unfailingly "that the disbelief in human evolution is the driving factor and most consistent predictor of prejudice in comparison to other relevant constructs," the paper states.

In the Israel-based study, people with a higher belief in evolution were more likely to support peace among Palestinians, Arabs and Jews. In the study involving countries in the Islamic world, belief in evolution was associated with less prejudice toward Christians and Jews. And in the study based in Eastern Europe, where Orthodox Christians are the majority, a belief in evolution was linked with less prejudice toward gypsies, Jews and Muslims.

Syropoulos posits that a belief in evolution may expand people's "moral circle," leading to a sense that "we have more in common than things that are different."

The findings also suggest that "teaching evolution seems to have side effects that might make for a better or more harmonious society," Leidner adds.

Read more at Science Daily

Tooth study prompts rethink of human evolution

A study into tooth wear in a group of wild Japanese macaques has significant implications for the study of human evolution, a University of Otago study has shown.

Lead author Dr Ian Towle and Dr Carolina Loch, of the Sir John Walsh Research Institute, in collaboration with colleagues from Japan, studied root grooves and large uniform scratches in the macaques' teeth, which had previously only been described in fossil humans.

"Unusual wear on our fossil ancestors' teeth is thought to be unique to humans and demonstrates specific types of tool use. These types of wear have also been considered some of the earliest evidence of cultural habits for our ancestors," Dr Towle says.

"However, our research suggests this idea may need reconsidering, since we describe identical tooth wear in a group of wild monkeys that do not use tools.

"This research raises questions for our understanding of cultural changes during human evolution and suggests we may need to reassess early evidence of cultural habits."

The study, published in the American Journal of Biological Anthropology, concluded the 'toothpick'-like grooves on back teeth and large uniform scratches on the macaques' front teeth were actually caused by something more mundane, yet still surprising -- eating shellfish from rocks and accidentally chewing grit and sand with their food.

This macaque group is well-known for undertaking remarkable behaviours, including washing foods in water, and consuming fish. They have been studied for more than 70 years and have not been seen using tools or other items that could cause the unusual tooth wear observed.

Dr Towle has been studying tooth wear and pathologies in a wide variety of primate species and was "extremely surprised" to find this type of tooth wear in a group of wild monkeys.

"Up until now, the large scratches in the front teeth of fossil humans have been considered to be caused by a behaviour called 'stuff and cut', in which an item such as an animal hide is held between the front teeth and a stone tool is used for slicing. Similarly, 'toothpick' grooves are thought to be caused by tools being placed between back teeth to remove food debris or relieve pain.

"Although this does not mean hominins were not placing tools in their mouths, our study suggests the accidental ingestion of grit and/or normal food processing behaviours could also be responsible for these atypical wear patterns."

Dr Towle believes the findings provide insight into how researchers interpret cultural changes through the course of human evolution.

Read more at Science Daily

Savannah chimpanzees, a model for the understanding of human evolution

To prosper, most great apes need lush forests in Africa (bonobos, chimpanzees, and gorillas) or Southeast Asia (orangutans), except for some groups of chimpanzees that live in savannahs, habitats characterised by high temperatures and very low seasonal rainfall.

Adriana Hernández, Serra Hunter professor at the Faculty of Psychology of the University of Barcelona, co-led the study conducted by an international team of primatologists who reviewed the existing research on the behaviour and ecology of savannah chimpanzees to understand how these apes adapt to extreme conditions.

According to the researchers, the environmental conditions of these places would lead to a specific type of behaviours and physiological responses in these chimpanzees -such as resting in caves or digging in order to get water- which are not observed in their counterparts that live in more forested areas, where they do not deal with these extreme environmental conditions.

"The study on savannah chimpanzees and what we call the landscape savannah effect have important implications for reconstructing the behaviour of the first hominis who lived in similar habitats and therefore, it helps us to better understand our own evolution," notes Adriana Hernández, who co-led the study, published in the journal Evolutionary Anthropology, together with Stacy Lindshield, from the University of Purdue (United States).

The genetically closest-to-humans evolutionary living relative

Chimpanzees (Pan troglodytes) are our closest living relatives, since they share 98.7% of their DNA with humans and have a common ancestor that lived between 4.5 and 6 million years ago. Despite this proximity, they lack some of the biological and cultural traits that humans possess to adapt to extreme heat, such as numerous eccrine sweat glands, relative lack of hair, or the ability to create artefacts such as water containers and sun hats to mitigate dehydration and sunstroke.

The chimpanzees that live in the savannah are taxonomically indistinguishable from other chimpanzees. For this reason, comparisons of behaviour, morphology and ecology with chimpanzees that live in more forested landscapes provide key information for hypothesising how early humans may have adapted millions of years ago while African forests were receding and gave place to savannahs.

"We know that early hominins adapted to savannah environments similar to those occupied by chimpanzees today, and researchers think that savannah conditions caused adaptations in our ancestors, such as brain expansion or tolerance to high temperatures," says Adriana Hernández, who is also the co-director of research at the Jane Goodall Institute Spain. "Therefore -she continues-, understanding how our genetically closest living relatives adapt to a dry, hot, seasonal and open environment, very similar to those where early hominins lived, helps us to model how our ancestors might have adapted and how the features that define us as humans might have emerged."

Strategies to adapt to high temperatures

Among the different characteristics of savannah chimpanzees described in the study, their strategies to deal with high temperatures stand out. "Understanding how they deal with heat can help us better understand what strategies human ancestors may have used to cope with high temperatures. Some strategies are probably the same for chimpanzees and hominins, such as the use of caves or going into water pools to cool down," notes the researcher. Another example the researcher highlights is the ways in which these chimpanzees try to hydrate themselves during the advanced dry season, such as digging for water when this resource is reduced to just a few spots in the landscape. "Early hominins also had to deal with low water availability during part of the year," Hernández adds.

Groups distributed over larger areas

The study also confirmed that chimpanzee social groups in the savannah are distributed over unusually large areas of around 100 km², while chimpanzees living in more forested areas have ranges between 3 and 30 km², approximately. "However, although group sizes are similar in different habitats, chimpanzees in the savannah have a much lower population density, which could be explained by the low availability of food in this habitat."

Despite the fact that we know much more about savannah chimpanzees now than ever before, their exact numbers are unknown, although according to the researchers "there are fewer than those living in the forest areas, as the total area they occupy is much smaller." In addition, because they have a lower population density, there are far fewer individuals in areas of the same size than in the forest. "It should be noted that there are far fewer sites where savannah chimpanzees have been studied, as there are only two study sites where savannah chimpanzees are habituated to humans and their behaviour can be observed directly. In contrast, there are many study sites where chimpanzees are fully habituated to researchers in the forest, a habitat where these primates have been studied for decades," explains Adriana Hernández.

Keys to understanding adaptation to climate change

Another important contribution of this study is that it helps to understand the potential effects of climate change on the species. "The adaptation of savannah chimpanzees to extreme climates can help us model how chimpanzees that currently inhabit forests might adapt to changes that climate studies project will make their environments drier and warmer. This is important, since the species is categorized as Endangered and the West African subspecies (Pan troglodytes verus) is Critically Endangered," says the expert.

Read more at Science Daily

'Dragon man' fossil may replace Neanderthals as our closest relative

A near-perfectly preserved ancient human fossil known as the Harbin cranium sits in the Geoscience Museum in Hebei GEO University. The largest of known Homo skulls, scientists now say this skull represents a newly discovered human species named Homo longi or "Dragon Man." Their findings, appearing in three papers publishing June 25 in the journal The Innovation, suggest that the Homo longi lineage may be our closest relatives -- and has the potential to reshape our understanding of human evolution.

"The Harbin fossil is one of the most complete human cranial fossils in the world," says author Qiang Ji, a professor of paleontology of Hebei GEO University. "This fossil preserved many morphological details that are critical for understanding the evolution of the Homo genus and the origin of Homo sapiens."

The cranium was reportedly discovered in the 1930s in Harbin City of the Heilongjiang province of China. The massive skull could hold a brain comparable in size to modern humans' but had larger, almost square eye sockets, thick brow ridges, a wide mouth, and oversized teeth. "While it shows typical archaic human features, the Harbin cranium presents a mosaic combination of primitive and derived characters setting itself apart from all the other previously-named Homo species," says Ji, leading to its new species designation of Homo longi.

Scientists believe the cranium came from a male individual, approximately 50 years old, living in a forested, floodplain environment as part of a small community. "Like Homo sapiens, they hunted mammals and birds, and gathered fruits and vegetables, and perhaps even caught fish," remarks author Xijun Ni, a professor of primatology and paleoanthropology at the Chinese Academy of Sciences and Hebei GEO University. Given that the Harbin individual was likely very large in size as well as the location where the skull was found, researchers suggest H. longi may have been adapted for harsh environments, allowing them to disperse throughout Asia.

Using a series of geochemical analyses, Ji, Ni, and their team dated the Harbin fossil to at least 146,000 years, placing it in the Middle Pleistocene, a dynamic era of human species migration. They hypothesize that H. longi and H. sapiens could have encountered each other during this era.

"We see multiple evolutionary lineages of Homo species and populations co-existing in Asia, Africa, and Europe during that time. So, if Homo sapiens indeed got to East Asia that early, they could have a chance to interact with H. longi, and since we don't know when the Harbin group disappeared, there could have been later encounters as well," says author Chris Stringer, a paleoanthropologist at the Nature History Museum in London.

Looking farther back in time, the researchers also find that Homo longi is one of our closest hominin relatives, even more closely related to us than Neanderthals. "It is widely believed that the Neanderthal belongs to an extinct lineage that is the closest relative of our own species. However, our discovery suggests that the new lineage we identified that includes Homo longi is the actual sister group of H. sapiens," says Ni.

Their reconstruction of the human tree of life also suggests that the common ancestor we share with Neanderthals existed even further back in time. "The divergence time between H. sapiens and the Neanderthals may be even deeper in evolutionary history than generally believed, over one million years," says Ni. If true, we likely diverged from Neanderthals roughly 400,000 years earlier than scientists had thought.

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Newly discovered African 'climate seesaw' drove human evolution

While it is widely accepted that climate change drove the evolution of our species in Africa, the exact character of that climate change and its impacts are not well understood. Glacial-interglacial cycles strongly impact patterns of climate change in many parts of the world, and were also assumed to regulate environmental changes in Africa during the critical period of human evolution over the last ~1 million years. The ecosystem changes driven by these glacial cycles are thought to have stimulated the evolution and dispersal of early humans.

A paper published in Proceedings of the National Academy of Sciences (PNAS) this week challenges this view. Dr. Kaboth-Bahr and an international group of multidisciplinary collaborators identified ancient El Niño-like weather patterns as the drivers of major climate changes in Africa. This allowed the group to re-evaluate the existing climatic framework of human evolution.

Walking with the rain

Dr. Kaboth-Bahr and her colleagues integrated 11 climate archives from all across Africa covering the past 620 thousand years to generate a comprehensive spatial picture of when and where wet or dry conditions prevailed over the continent. "We were surprised to find a distinct climatic east-west 'seesaw' very akin to the pattern produced by the weather phenomena of El Niño, that today profoundly influences precipitation distribution in Africa," explains Dr. Kaboth-Bahr, who led the study.

The authors infer that the effects of the tropical Pacific Ocean on the so-called "Walker Circulation" -- a belt of convection cells along the equator that impact the rainfall and aridity of the tropics -- were the prime driver of this climate seesaw. The data clearly shows that the wet and dry regions shifted between the east and west of the African continent on timescales of approximately 100,000 years, with each of the climatic shifts being accompanied by major turnovers in flora and mammal fauna.

"This alternation between dry and wet periods appeared to have governed the dispersion and evolution of vegetation as well as mammals in eastern and western Africa," explains Dr. Kaboth-Bahr. "The resultant environmental patchwork was likely to have been a critical component of human evolution and early demography as well."

The scientists are keen to point that although climate change was certainly not the sole factor driving early human evolution, the new study nevertheless provides a novel perspective on the tight link between environmental fluctuations and the origin of our early ancestors.

"We see many species of pan-African mammals whose distributions match the patterns we identify, and whose evolutionary history seems to articulate with the wet-dry oscillations between eastern and western Africa," adds Dr. Eleanor Scerri, one of the co-authors and an evolutionary archaeologist at the Max Planck Institute for the Science of Human History in Germany. "These animals preserve the signals of the environments that humans evolved in, and it seems likely that our human ancestors may have been similarly subdivided across Africa as they were subject to the same environmental pressures."

Ecotones: the transitional regions between different ecological zones

The scientists' work suggests that a seesaw-like pattern of rainfall alternating between eastern and western Africa probably had the effect of creating critically important ecotonal regions -- the buffer zones between different ecological zones, such grassland and forest.

"Ecotones provided diverse, resource-rich and stable environmental settings thought to have been important to early modern humans," adds Dr. Kaboth-Bahr. "They certainly seem to have been important to other faunal communities."

To the scientists, this suggests that Africa's interior regions may have been critically important for fostering long-term population continuity. "We see the archaeological signatures of early members of our species all across Africa," says Dr. Scerri, "but innovations come and go and are often re-invented, suggesting that our deep population history saw a constant saw-tooth like pattern of local population growth and collapse. Ecotonal regions may have provided areas for longer term population continuity, ensuring that the larger human population kept going, even if local populations often went extinct."

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Gorillas display territorial behavior

Scientists have discovered that gorillas really are territorial -- and their behaviour is very similar to our own.

Published in the journal Scientific Reports, the research shows for the first time that groups of gorillas recognise "ownership" of specific regions. They are also more likely to avoid contact with other groups the closer they are to the centre of their neighbours' home range, for fear of conflict.

The study, which was carried out by academics from the University of Cambridge, Anglia Ruskin University (ARU), the University of Barcelona, SPAC Scientific Field Station Network, and the University of Vienna, involved monitoring the movements of groups of western lowland gorillas (Gorilla gorilla gorilla).

Western lowland gorillas are difficult to track on foot because they live in dense forests. Instead, the scientists followed eight groups of gorillas using a network of cameras placed at 36 feeding "hotspots" across a 60km2 area of the Odzala-Kokoua National Park in the Republic of Congo.

It was previously thought that gorillas were non-territorial, due to the overlap of home ranges and their tolerance of other groups. This is markedly different to chimpanzees, which display extreme territorial-based violence.

However, this new research discovered that gorillas display more nuanced behaviours, and their movements are strongly influenced by the location of their neighbours -- they are less likely to feed at a site visited by another group that day -- and the distance from the centre of their neighbours' home range.

Lead author Dr Robin Morrison, who carried out the study during her PhD at the University of Cambridge, said: "Our findings indicate that there is an understanding among gorillas of 'ownership' of areas and the location of neighbouring groups restricts their movement.

"Gorillas don't impose hard boundaries like chimpanzees. Instead, gorilla groups may have regions of priority or even exclusive use close to the centre of their home range, which could feasibly be defended by physical aggression.

"At the same time groups can overlap and even peacefully co-exist in other regions of their ranges. The flexible system of defending and sharing space implies the presence of a complex social structure in gorillas."

Co-author Dr Jacob Dunn, Reader in Evolutionary Biology at Anglia Ruskin University (ARU), said: "This new research changes what we know about how groups of gorillas interact and has implications for what we understand about human evolution.

"Almost all comparative research into human evolution compares us to chimpanzees, with the extreme territorial violence observed in chimpanzees used as evidence that their behaviour provides an evolutionary basis for warfare among humans.

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Human Populations survived the Toba volcanic super-eruption 74,000 years ago

The Toba super-eruption was one of the largest volcanic events over the last two million years, about 5,000 times larger than Mount St. Helen's eruption in the 1980s. The eruption occurred 74,000 years ago on the island of Sumatra, Indonesia, and was argued to have ushered in a "volcanic winter" lasting six to ten years, leading to a 1,000 year-long cooling of the Earth's surface. Theories purported that the volcanic eruption would have led to major catastrophes, including the decimation of hominin populations and mammal populations in Asia, and the near extinction of our own species. The few surviving Homo sapiens in Africa were said to have survived by developing sophisticated social, symbolic and economic strategies that enabled them to eventually re-expand and populate Asia 60,000 years ago in a single, rapid wave along the Indian Ocean coastline.

Fieldwork in southern India conducted in 2007 by some of this study's authors challenged these theories, leading to major debates between archaeologists, geneticists and earth scientists about the timing of human dispersals Out of Africa and the impact of the Toba super-eruption on climate and environments. The current study continues the debate, providing evidence that Homo sapiens were present in Asia earlier than expected and that the Toba super-eruption wasn't as apocalyptic as believed.

The Toba volcanic super-eruption and human evolution

The current study reports on a unique 80,000 year-long stratigraphic record from the Dhaba site in northern India's Middle Son Valley. Stone tools uncovered at Dhaba in association with the timing of the Toba event provide strong evidence that Middle Palaeolithic tool-using populations were present in India prior to and after 74,000 years ago. Professor J.N. Pal, principal investigator from the University of Allahabad in India notes that "Although Toba ash was first identified in the Son Valley back in the 1980s, until now we did not have associated archaeological evidence, so the Dhaba site fills in a major chronological gap."

Professor Chris Clarkson of the University of Queensland, lead author of the study, adds, "Populations at Dhaba were using stone tools that were similar to the toolkits being used by Homo sapiens in Africa at the same time. The fact that these toolkits did not disappear at the time of the Toba super-eruption or change dramatically soon after indicates that human populations survived the so-called catastrophe and continued to create tools to modify their environments." This new archaeological evidence supports fossil evidence that humans migrated out of Africa and expanded across Eurasia before 60,000 years ago. It also supports genetic findings that humans interbred with archaic species of hominins, such as Neanderthals, before 60,000 years ago.

Toba, climate change and human resilience

Though the Toba super-eruption was a colossal event, few climatologists and earth scientists continue to support the original formulation of the "volcanic winter" scenario, suggesting that the Earth's cooling was more muted and that Toba may not have actually caused the subsequent glacial period. Recent archaeological evidence in Asia, including the findings unearthed in this study, does not support the theory that hominin populations went extinct on account of the Toba super-eruption.

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