Modern humans first left Africa 100,000 years ago in a series of slow-paced migration waves and arrived in southern Europe around 80,000-90,000 years ago, far earlier than previously believed, according to a new study.

The research suggests that humans spread out across the globe in four migration events driven by climate change, connected to variations in the Earth's orbit.

The results challenge traditional models that suggest there was a single exodus out of Africa around 60,000 years ago.

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The researchers modelled human migration 80,000 years ago. The model simulates the arrival in Eastern China and Southern Europe and migration out of Africa along vegetated corridors in Sinai and the Arabian Peninsula

IMPORTANCE OF THE STUDY Chris Stringer, Research Leader in Human Origins at the Natural History Museum London told MailOnline the research is 'the most comprehensive climate, vegetation and human-dispersal modelling study published so far'. 'While the earliest [migration] wave had only limited further penetration across the rest of Eurasia, they [the researchers] argue that modern humans could have arrived in small numbers in China and southern Europe by about 80,000 years,' he explained. 'While the former dispersal is now supported by some fossil evidence, such an early arrival in Europe (more than 35,000 years earlier than usually considered) has no archaeological or fossil support at present. 'The authors speculate that European Neanderthals might have assimilated the small numbers of moderns in this early dispersal wave. However, this is something which has not been detected in ancient DNA studies so far.' Advertisement

Changes in the climate, coupled with the wobble of the Earth's axis, are known to have caused massive shifts in vegetation in tropical and subtropical regions, which opened up green corridors between Africa, the Sinai and the Arabian Peninsula.

This was thought to have enabled early members of our species, Homo sapiens, to leave North east Africa and embark onto their grand journey into Asia, Europe, Australia, and eventually into the Americas.

But whether climate shifts really did influence early human migration has been a matter of intense debate.

To explore the idea, researchers from the International Pacific Research Center (IPRC) at the University of Hawaii at Mānoa (UHM) used one of the first integrated climate-human migration computer models to re-create the spread of Homo sapiens over the past 125,000 years.

The model simulates ice-ages, abrupt climate change and captures the arrival times of Homo sapiens in the Eastern Mediterranean, Arabian Peninsula, Southern China, and Australia in close agreement with paleoclimate reconstructions and fossil and archaeological evidence.

The researchers found that modern humans appear to have been constrained within Africa until around 100,000 years ago when changes in the climate allowed them to spread rapidly into the Middle East and Asia (illustrated)

Between 90,000 and 80,000 years ago, Homo sapiens had spread as far east as southern China and were making inroads into southern Europe, far earlier than believed (illustrated)

WHAT THE FOUR STUDIES TELL US ABOUT HUMAN ANCESTRY The Simons Genome Diversity Project study After analysing DNA from 142 populations around the world, the researchers conclude that all modern humans living today can trace their ancestry back to a single group that emerged in Africa 200,000 years ago. They also found that all non-Africans appear to be descended from a single group that split from the ancestors of African hunter gatherers around 130,000 years ago. The study also shows how humans appear to have formed isolated groups within Africa with populations on the continent separating from each other. The KhoeSan in south Africa for example separated from the Yoruba in Nigeria around 87,000 years ago while the Mbuti split from the Yoruba 56,000 years ago. The Estonian Biocentre Human Genome Diversity Panel study This examined 483 genomes from 148 populations around the world to examine the expansion of Homo sapiens out of Africa. They found that indigenous populations in modern Papua New Guinea owe two percent of their genomes to a now extinct group of Homo sapiens. This suggests there was a distinct wave of human migration out of Africa around 120,000 years ago. The Aboriginal Australian study Using genomes from 83 Aboriginal Australians and 25 Papuans from New Guinea, this study examined the genetic origins of these early Pacific populations. These groups are thought to have descended from some of the first humans to have left Africa and has raised questions about whether their ancestors were from an earlier wave of migration than the rest of Eurasia. The new study found that the ancestors of modern Aboriginal Australians and Papuans split from Europeans and Asians around 58,000 years ago following a single migration out of Africa. These two populations themselves later diverged around 37,000 years ago, long before the physical separation of Australia and New Guinea some 10,000 years ago. The Climate Modelling study Researchers from the University of Hawaii at Mānoa used one of the first integrated climate-human migration computer models to re-create the spread of Homo sapiens over the past 125,000 years. The model simulates ice-ages, abrupt climate change and captures the arrival times of Homo sapiens in the Eastern Mediterranean, Arabian Peninsula, Southern China, and Australia in close agreement with paleoclimate reconstructions and fossil and archaeological evidence. The found that it appears modern humans first left Africa 100,000 years ago in a series of slow-paced migration waves. They estimate that Homo sapiens first arrived in southern Europe around 80,000-90,000 years ago, far earlier than previously believed. The results challenge traditional models that suggest there was a single exodus out of Africa around 60,000 years ago. Advertisement

It identifies prominent glacial migration waves across the Arabian Peninsula and the Levant region around 106,000–94,000, 89,000–73,000, 59,000–47,000 and 45,000–29,000 years ago.

It also shows an almost simultaneous early arrival of Homo sapiens in southern China and Europe about 90,000–80,000 years ago.

Recent fossils - identified as being unequivocally Homo sapien - were discovered in southern China and were last year dated to be 80,000-years-old.

'One of the surprising results of our study is that the scenario that agrees best with all the Asian data is one that also simulates a very early arrival of Homo sapiens in Europe around 80,000-90,000 years ago, pre-dating the oldest fossil evidence by about 45,000 years,' said Axel Timmermann, lead author of the study, which is published in the journal Nature.

Co-author Tobias Friedrich added: 'The green migration gateway that opened up between Africa and Eurasia 110,000-95,000 years ago would have also promoted a low-density migration into Southern Europe and possibly a weak early interbreeding with Neanderthals.'

The green migration gateway that opened up between Africa and Eurasia 110,000-95,000 years ago would have also promoted a low-density migration into Southern Europe and possibly a weak early interbreeding with Neanderthals (reconstruction pictured)

The study, one of four looking at early human migration published in Nature, shows that every 20,000 years, warmer and wetter northern hemisphere tropical summers boosted human migration and saw an exchange of humans between Africa and Eurasia.

Professor Timmermann said: 'In our model simulation we see a complex pattern of human dispersal out of Africa and back flow into Africa, that challenges the more unidirectional away-from-Africa perspective that is still very prevalent in anthropology and some genetic studies.'

CLIMATE CHANGE WILL MAKE ANIMALS SEEK NEW HOMES Researchers have found that climate change is altering ecosystems across the globe, and many species may soon have to migrate to follow the conditions necessary for their survival. In a previous study, they determined that the Amazon Basin, southeastern United States, and southeastern Brazil will have high densities of climate-driven movement, Cool Green Science explains. But, according to the new research, just 41 percent of the natural land area in the US 'retains enough connectivity to facilitate species tracking their preferred climate conditions as the global climate changes.' While the map highlights the big picture view of the phenomenon rather than local patterns, they do show how human development could soon pose challenges to these migrating species - but the researchers say there are ways we can help. 'There are a number of ways that conservationists and land managers can re-build or maintain connectivity to improve species' ability to adapt to warmer temperatures,' the researchers explain. 'Removing fencing, adding wildlife overpasses (or underpasses) to major roadways, and better routing of infrastructure like pipelines and powerlines can all help re-connect areas fragmented by human development.' Advertisement

The findings promise to transform the way anthropologists view early fossils of modern human and their spread around the world.

Previous ice core and marine sediment core studies have found evidence during glacial periods for rapid climate transitions between cold and warm periods on timescales of a human lifetime.

The new study addresses for the first time with a computer model whether these naturally occurring climate shifts influenced global human migration patterns.

Comparing simulations of the human migration model with and without these climate fluctuations, the researchers found only regional impacts on simulated human density in areas extending from northern Africa to Europe.

Professor Timmermann said: 'According to our results, the global-scale migration patterns were not affected by past abrupt climate change events on timescales of decades.'

The team next plans to include Neanderthals in its computer model and account for food competition, interbreeding and cultural developments to get a better idea of how modern man eventually came to populate Earth.



