Modern humans out of Africa sooner than thought

"The model that is generally accepted is that modern humans left Africa only 50,000 years ago," said Maria Martinon-Torres, a researcher at University College London and a co-author of the study.

Human teeth discovered in southern China provide evidence that our species left the African continent up to 70,000 years earlier than prevailing theories suggest, a study published on Wednesday said.

Homo sapiens reached present-day China 80,000-120,000 years ago, according to the study, which could redraw the migration map for modern humans.

"In this case, we are saying the H. sapiens is out of Africa much earlier," she told the peer-reviewed journal Nature, which published the study.

While the route they travelled remains unknown, previous research suggests the most likely path out of East Africa to east Asia was across the Arabian Peninsula and the Middle East.

The findings also mean that the first truly modern humans—thought to have emerged in east Africa some 200,000 years ago—landed in China well before they went to Europe.

There is no evidence to suggest that H. sapiens entered the European continent earlier than 45,000 years ago, at least 40,000 years after they showed up in present-day China.

The 47 teeth exhumed from a knee-deep layer of grey, sandy clay inside the Fuyan Cave near the town of Daoxian closely resemble the dental gear of "contemporary humans," according to the study.

They could only have come from a population that migrated from Africa, rather than one that evolved from an another species of early man such as the extinct Homo erectus, the authors said.

The scientists also unearthed the remains of some 38 mammals, including specimens of five extinct species, one of them a giant panda larger than those in existence today.

No tools were found.

"Judging by the cave environment, it may not have been a living place for humans," lead author Wu Liu from the Chinese Academy of Science in Beijing told AFP.

Why not Europe?

The study, published in the journal Nature, also rewrites the timeline of early man in China. Up to now, the earliest proof of H. sapiens east of the Arabian Peninsula came from the Tianyuan Cave near Beijing, and dated from no more than 40,000 years ago.

The new discovery raises questions about why it took so long for H. sapiens to find their way to nearby Europe. "Why is it that modern humans—who were already at the gates—didn't really get into Europe?", Martinon-Torres asked. Wu and colleagues propose two explanations.

The first is the intimidating presence of Neanderthal man. While this species of early human eventually died out, they were spread across the European continent up until at least some 50,000 years ago.

"The classic idea is that H. sapiens... took over the Neanderthal empire, but maybe Neanderthals were a kind of ecological barrier, and Europe was too small a place" for both, Martinon-Torres said. Another impediment might have been the cold.

Up until the Ice Age ended 12,000 years ago, ice sheets stretched across a good part of the European continent, a forbidding environment for a new species emerging from the relative warmth of East Africa.

"H. sapiens originated in or near the tropics, so it makes sense that the species' initial dispersal was eastwards rather than northwards, where winter temperatures rapidly fell below freezing," Robin Dennell of the University of Exeter said in a commentary, also in Nature.

Martinon-Torres laid out some of the questions to be addressed in future research, using both genetics and fossil records.

A near miss

"What are the origins of these populations, and what was their fate? Did they vanish? Could they be the ancestors of later and current populations that entered Europe?"

She also suggested there might have been "different movements and migrations" out of Africa, not just one. Besides the prehistoric panda, called Ailuropoda baconi, the scientists found an extinct species of a giant spotted hyaena.

An elephant-like creature called Stegodon orientalis and a giant tapir, also present, were species that may have survived into the era when the Chinese had developed writing, some 3500 years ago.

The cache of teeth nearly went unnoticed, Wu told AFP.

He and his Chinese colleagues discovered the cave—and its menagerie of long-deceased animals—in the 1980s, but had no inkling that it also contained human remains.

But 25 years later, while revisiting the site, Wu had a hunch.

"By thinking about the cave environment, we realised that human fossils might be found there," he told AFP by email. "So we started a five-year excavation."
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Reference:

Phys.Org. 2016. “Modern humans out of Africa sooner than thought”. Phys.Org. Posted: October 14, 2015. Available online: http://phys.org/news/2015-10-modern-humans-africa-sooner-thought.html

Homo sapiens ‘culturally diverse’ prior to leaving Africa

Researchers have carried out the largest comparative study of stone tools dating to between 130,000 and 75,000 years ago found in the region between sub-Saharan Africa and Eurasia. The study is crucial to understanding the structure and variation of Homo sapiens populations in Africa and then trying to interpret evidence of their subsequent dispersals into Eurasia.

As part of this work they have discovered marked differences in the way stone tools were made, reflecting the development of diversity in cultural traditions. The study has also identified at least four distinct populations, each relatively isolated from the other and with their own different cultural characteristics.

Movement and exchange

The research paper also suggests that early populations took advantage of rivers and lakes that criss-crossed the Saharan desert for movement and exchange. A climate model coupled with data about these ancient water courses was matched with the new findings on stone tools to reveal that populations connected by rivers had recognisable similarities in their cultures.

This could be the earliest evidence of different populations ‘budding’ across the Sahara, using the rivers to disperse and meet people from other populations, according to the paper published in the journal, Quaternary Science Reviews.

The researchers from the University of Oxford, Kings College London and the University of Bordeaux took a staggering 300,000 measurements of stone tools from 17 archaeological sites across North Africa, including the Sahara, and then combined the stone tool data with a model of the North African environment during that period, which showed that the Sahara was then a patchwork of savannah, grasslands and water, interspersed with desert.

Mapping out known ancient rivers and major lakes has built on earlier research by Professor Nick Drake, one of this paper’s co-authors. By modelling and mapping the environment, the researchers were then able to draw new inferences on the contexts in which the ancient populations made and used their tools. The results show, for the first time, how early populations of modern humans dispersed across the Sahara, one after the other ‘budding’ into populations along the ancient rivers and watercourses.

Lead researcher Dr Eleanor Scerri, visiting scholar at the University of Oxford, said: ‘This is the first time that scientists have identified that early modern humans at the cusp of dispersal out of Africa were grouped in separate, isolated and local populations. Stone tools are the only form of preserved material culture for most of human history. In Africa, owing to the hot climate, ancient DNA has not yet been found. These stone tools reveal how early populations of modern humans dispersed across the Sahara just before they left North Africa. While different populations were relatively isolated, we were interested to find that when connected by rivers, they share similarities in their tool-making suggesting some interaction with one another.”

Consistently culturally distinctive

The researchers used a variety of tests in order to rule out causes of variability, such as differences in raw materials. This was done to establish that tool-making traditions were consistently culturally distinctive among the different populations in the study.

Dr Scerri said: “Not much is known about the structure of early modern human populations in Africa, particularly at the time of their earliest dispersals into Eurasia. Our picture of modern human demography around 100,000 years ago is that there were a number of populations, varying in size and degree of genetic contact, distributed over a wide geographical area. This model of our population history supports other theories recently put forward that modern humans may have first successfully left Africa earlier than 60,000-50,000 years ago, which had been the common view among scholars. Our work provides important new evidence that sheds light on both the timing of early modern human dispersals out of Africa and the character of our interaction with other human species, such as Neanderthals.”

Co-author Dr Huw Groucutt, from the School of Archaeology at the University of Oxford, said: ‘The question of whether there was an early successful exit from Africa has become one of whether any of the populations discovered in this paper went in and out of Africa for some or all of this time. A crucial next step involves fieldwork in areas such as the Arabian Peninsula to understand how these populations spread into Eurasia. The ongoing fieldwork by the Oxford University based Palaeodeserts Project is seeking to do exactly that, and we are making some remarkable discoveries in the deserts of Arabia, which may also have been the region where both Neanderthal and Homo sapiens populations may have interacted.”
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References:

Past Horizons. 2014. “Homo sapiens ‘culturally diverse’ prior to leaving Africa”. Past Horizons. Posted: August 26, 2014. Available online: http://www.pasthorizonspr.com/index.php/archives/08/2014/homo-sapiens-culturally-diverse-prior-to-leaving-africa

Ancient Arabian Stones Hint at How Humans Migrated Out of Africa

Ancient stone artifacts recently excavated from Saudi Arabia possess similarities to items of about the same age in Africa — a discovery that could provide clues to how humans dispersed out of Africa, researchers say.

Modern humans originated about 200,000 years ago in Africa. However, scientists have long debated when and how the modern human lineage spread out of Africa.

"Understanding how we originated and colonized the world remains one of the most fascinating and enduring questions, because it is our story as humans," said lead study author Eleanor Scerri, an archaeologist at the University of Bordeaux in France.

Previous research had suggested that the exodus from Africa started between 70,000 and 40,000 years ago. However, a genetic analysis reported in April hinted that modern humans might have begun their march across the globe as early as 130,000 years ago, and continued their expansion out of Africa in multiple waves.

In addition, stone artifacts recently unearthed in the Arabian Desert date to at least 100,000 years ago. This could be evidence of an early modern-human exodus out of Africa, scientists say. However, it's possible that these artifacts weren't created by modern humans; a number of now-extinct human lineages existed outside Africa before or at the same time when modern humans migrated there. For instance, the Neanderthals, the closest known extinct relatives of modern humans, lived in both Europe and Asia around that time.

To help shed light on the role the Arabian Peninsula might have played in the history of modern humans, scientists compared stone artifacts recently excavated from three sites in the Jubbah lake basin in northern Saudi Arabia with items from northeast Africa excavated in the 1960s. Both sets of artifacts were 70,000 to 125,000 years old. Back then, the areas that are now the Arabian and Sahara deserts were far more hospitable places to live than they are now, which could have made it easier for modern humans and related lineages to migrate out of Africa.

"Far from being a desert, the Arabian Peninsula between 130,000 and 75,000 years ago was a patchwork of grasslands and savanna environments, featuring extensive river networks running through the interior," Scerri said.

The northeast African stone tools the researchers analyzed were similar to ones previously found near modern-human skeletons. The scientists found that stone artifacts at two of the three Arabian sites were "extremely similar" to the northeast African stone tools, Scerri told Live Science. At the very least, Scerri said, this finding suggests that there was some level of interaction between the groups in Africa and those in the Arabian Peninsula, and might hint that these Arabian tools were made by modern humans.

Surprisingly, Scerri said, tools from the third Arabian site the researchers analyzed were "completely different." "This shows that there was a number of different tool-making traditions in northern Arabia during this time, often in very close proximity to each other," she said.

One possible explanation for these differences is that the artifacts were made by different human lineages. Future research needs to uncover skeletal remains with ancient tools unearthed from the Arabian Peninsula to help solve this mystery, Scerri noted. Unless skeletal remains are found near such artifacts, it will remain uncertain whether modern humans or a different  human lineage might have made them.

"It seems likely that there were multiple dispersals into the Arabian Peninsula from Africa, some possibly very early in the history of Homo sapiens," Scerri said. "It also seems likely that there may have been multiple dispersals into this region from other parts of Eurasia. These features are what make the Arabian Peninsula so interesting."

Ancient migrants out of Africa and from Eurasia might have encountered a number of different populations in the Arabian Peninsula, Scerri said. Some of these groups may have adapted to their environment more than others had, which raises the intriguing question: "Did the exchange of genes and knowledge between such groups contribute to our ultimate success as a species?" Scerri said.

The scientists detailed their findings online Aug. 8 in the Journal of Human Evolution.
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References:

Choi, Charles Q. 2014. “Ancient Arabian Stones Hint at How Humans Migrated Out of Africa”. Live Science. Posted: August 26, 2014. Available online: http://www.livescience.com/47555-stone-artifacts-human-migration.html

Tracing humanity's African ancestry may mean rewriting 'out of Africa' dates

UAlberta archeologist's new research may lead to rethinking how and when our ancestors left Africa to colonize the globe

New research by a University of Alberta archeologist may lead to a rethinking of how, when and from where our ancestors left Africa.

U of A researcher and anthropology chair Pamela Willoughby's explorations in the Iringa region of southern Tanzania yielded fossils and other evidence that records the beginnings of our own species, Homo sapiens. Her research, recently published in the journal Quaternary International, may be key to answering questions about early human occupation and the migration out of Africa about 60,000 to 50,000 years ago, which led to modern humans colonizing the globe.

From two sites, Mlambalasi and nearby Magubike, she and members of her team, the Iringa Region Archaeological Project, uncovered artifacts that outline continuous human occupation between modern times and at least 200,000 years ago, including during a late Ice Age period when a near extinction-level event, or "genetic bottleneck," likely occurred.

Now, Willoughby and her team are working with people in the region to develop this area for ecotourism, to assist the region economically and create incentives to protect its archeological history.

"Some of these sites have signs that people were using them starting around 300,000 years ago. In fact, they're still being used today," she said. "But the idea that you have such ancient human occupation preserved in some of these places is pretty remarkable."

Magubike: Home to a modern Stone Age family?

Willoughby says one of the fascinating things about Magubike is the presence of a large rock shelter with an intact overhanging roof. The excavations yielded unprecedented ancient artifacts and fossils from under this roof. Samples from the site date from the earliest stages of the middle Stone Age to the Iron Age. The earlier deposits include human teeth and artifacts such as animal bones, shells and thousands of flaked stone tools.

The Iron Age finds can be dated using radiocarbon, but the older deposits must go through more specialized processes, such as electron spin resonance, to determine their age. Other parts of the Magubike rock shelter, excavated in 2006 and 2008, include occupations from after the middle Stone Age. Taken together, this information could be crucial to tracking the evolutionary development of the inhabitants.

"What's important about the whole sequence is that we may have a continuous record of human occupation," said Willoughby. "If we do—and we can prove it through these special dating techniques—then we have a place people lived in over the bottleneck."

Rugged, hilly terrain may have been key to survival

The team made similar findings at Mlambalasi, about 20 kilometres from Magubike. Among the findings at this site was a fragmentary human skeleton that probably dates to the late Pleistocene Ice Age—after the out-of-Africa expansion but at the end of the bottleneck period. The bottleneck theory explains what geneticists have found by studying the mitochondrial DNA of living people—that all non-Africans are descended from one lineage of people who left Africa about 50,000 years ago.

Reconstructions of past environments through pollen and other archeological records in Iringa suggest that people abandoned the lowland, tropical and coastal areas during that period but remained in the highlands, where vegetation has remained mostly unchanged over the last 50,000 years. Those who moved to higher ground may have found what is likely one of the few places that facilitated their survival and forced their adaptation. Further testing will determine whether these findings point to a clearer link to our African ancestors—a find Willoughby says could put that region of Tanzania on many archeologists' radar.

"It was only about 20 years ago that people recognized that modern Homo sapiens actually had an African ancestry, and everyone was focused on looking at early Homo sapiens in Europe who appeared around 40,000 years ago," she said. "But we now know that as far as back as around 200,000 years ago, Africa was inhabited by people who were already physically exactly like us today or really close to being the same as us. All of a sudden, it's not Europe in this time period that's really important, it's Africa."

Engaging community yields co-operation, opportunity

Along with its scientific significance, Willoughby's work may be a linchpin to potential economic growth for the region. Since 2005, when a local cultural officer showed her the sites, she has been sharing information about her research with local citizens, schools and government—opening up opportunities for more research and co-operation. She keeps the region informed of the team's findings through posters distributed around Iringa, and has asked for and accepted assistance from local scholars. Now the community is also looking for her help in establishing the historic sites as a tourist attraction that will benefit the region.

Willoughby says she feels fortunate to have the support of the Tanzanian people. She tells people it is a shared history she is uncovering, something she is honoured to be able to do.

"They're telling me, 'You're putting Iringa on the map,'" she said. "As long as they keep letting me work there, and keep letting the people working with me work there, we'll be happy."
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References:

EurekAlert. 2012. “Tracing humanity's African ancestry may mean rewriting 'out of Africa' dates”. EurekAlert. Posted: December 13, 2012. Available online: http://www.eurekalert.org/pub_releases/2012-12/uoa-tha121312.php

New Stanford analysis provides fuller picture of human expansion from Africa

A comprehensive analysis of the anthropological and genetic history of humans' expansion out of Africa could lead to medical advances.

A new, comprehensive review of humans' anthropological and genetic records gives the most up-to-date story of the "Out of Africa" expansion that occurred about 45,000 to 60,000 years ago.

This expansion, detailed by three Stanford geneticists, had a dramatic effect on human genetic diversity, which persists in present-day populations. As a small group of modern humans migrated out of Africa into Eurasia and the Americas, their genetic diversity was substantially reduced.

In studying these migrations, genomic projects haven't fully taken into account the rich archaeological and anthropological data available, and vice versa. This review integrates both sides of the story and provides a foundation that could lead to better understanding of ancient humans and, possibly, genomic and medical advances.

"People are doing amazing genome sequencing, but they don't always understand human demographic history" that can help inform an investigation, said review co-author Brenna Henn, a postdoctoral fellow in genetics at the Stanford School of Medicine who has a PhD in anthropology from Stanford. "We wanted to write this as a primer on pre-human history for people who are not anthropologists."

This model of the Out of Africa expansion provides the framework for testing other anthropological and genetic models, Henn said, and will allow researchers to constrain various parameters on computer simulations, which will ultimately improve their accuracy.

"The basic notion is that all of these disciplines have to be considered simultaneously when thinking about movements of ancient populations," said Marcus Feldman, a professor of biology at Stanford and the senior author of the paper. "What we're proposing is a story that has potential to explain any of the fossil record that subsequently becomes available, and to be able to tell what was the size of the population in that place at that time."

The anthropological information can inform geneticists when they investigate certain genetic changes that emerge over time. For example, geneticists have found that genes that allowed humans to tolerate lactose and gluten began to emerge in populations expanding into Europe around 10,000 years ago.

The anthropological record helps explain this: It was around this time that humans embraced agriculture, including milk and wheat production. The populations that prospered – and thus those who survived to pass on these mutations – were those who embraced these unnatural food sources. This, said Feldman, is an example of how human movements drove a new form of natural selection.

Populations that expand from a small founding group can also exhibit reduced genetic diversity – known as a "bottleneck" – a classic example being the Ashkenazi Jewish population, which has a fairly large number of genetic diseases that can be attributed to its small number of founders. When this small group moved from the Rhineland to Eastern Europe, reproduction occurred mainly within the group, eventually leading to situations in which mothers and fathers were related. This meant that offspring often received the same deleterious gene from each parent and, as this process continued, ultimately resulted in a population in which certain diseases and cancers are more prevalent.

"If you know something about the demographic history of populations, you may be able to learn something about the reasons why a group today has a certain genetic abnormality – either good or bad," Feldman said. "That's one of the reasons why in our work we focus on the importance of migration and history of mixing in human populations. It helps you assess the kinds of things you might be looking for in a first clinical assessment. It doesn't have the immediacy of prescribing chemotherapy – it's a more general look at what's the status of human variability in DNA, and how might that inform a clinician." The study is published in the current edition of the Proceedings of the National Academy of Sciences and was co-authored by Feldman's longtime collaborator, population geneticist Luigi Luca Cavalli-Sforza of Stanford and the Università Vita-Salute San Raffaele in Italy.
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References:

Carey, Bjorn. 2012. “New Stanford analysis provides fuller picture of human expansion from Africa”. Stanford University News Service. Posted: October 22, 2012. Available online: http://news.stanford.edu/pr/2012/pr-genetic-human-evolution-102212.html