Early humans left Africa earlier than expected

The first of several waves of emigration started 130, 000 years ago

Representation of the out-of-Arica model that best matches both the genetic and anatomical data of the skull: a first group of anatomically modern humans migrated along the edge of the Indian Ocean 130, 000 years ago (green arrow), followed by a second, younger wave of emigration to Eurasia (red arrow). © Katerina Harvati / University of Tübingen / Senckenberg
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From Africa to the whole world - but when did our ancestors set off from the "cradle of humanity"? A European team of researchers has studied more closely the migrations of early humans, stating that they left Africa much earlier than previously thought. In addition, there was not only a wave of emigration but at least two, the scientists write in the journal "Proceedings of the National Academy of Sciences".

The ancestors of today's humans lived in Africa 100, 000 to 200, 000 years ago, in which most scientists agree. About 50, 000 to 75, 000 years ago, they started to spread across the world from this common source population. Research confirms this "out-of-Africa" ​​hypothesis: The greater geographical distance from sub-Saharan Africa reduces the genetic and morphological diversity of humans. According to the theory, this is due to the fact that in the course of the migration movement only a part of the population continued to move on - the whole gene pool therefore always decreased slightly from one stage to the next.

However, it was unclear so far whether our ancestors made their way in a single migration, or whether there were several such emigration waves. The researchers, led by Katerina Harvati from the University of Tübingen, wanted to verify this: The scientists from Germany, France and Italy used data from anatomical skull comparisons of today's humans from different regions as well as genetic information. These balanced them with the necessary distances on various possible routes of propagation of the early humans. Using the genetic data, they also calculated the time periods in which the population split up. From the combined data, the researchers were able to deduce which propagation scenario is most likely.

Presentation of the examined anatomical points: By means of the Schl fenbeins the population history of the anatomically modern humans can be pursued better than on the basis of other skull areas. These data were therefore used in the study to conclude migration patterns in addition to the genetic data. Shown here is the average shape of the temporal bone of all individuals studied in the study. Katerina Harvati / University of T bingen / Senckenberg

First group spread to Australia

The results call into question the current perspective: A first group of our ancestors already broke out of Africa some 130, 000 years ago, from .000 50, 000 to 80, 000 years earlier than previously thought. This group spread along the coast of the Arabian Peninsula to Australia and the western Pacific. "Both sets of evidence, both anatomical skull comparisons and genetic data, support multiple waves of emigration, " says Harvati.

"Australians, Papuans and Melanesians initially remained relatively isolated after this early spread via the Southern route", explains first author Hugo Reyes-Centeno of the University of T bingen. Other Asian populations, on the other hand, seem to have come from a later wave of emigration from Africa to northern Eurasia some 50, 000 years ago

Cause unclear

Why did the Frihmen go on a journey at all, can so far only speculate may have been forced by strong D rrezeiten to seek a new fertile home. The researchers assume that further field studies as well as more detailed genetic analyzes will further secure the results on the migration routes of prehistoric people. You can also provide more details about individual stages and their times.

Scientists are particularly encouraged by the southern migration route: it covers a large geographical area, in which only a few archaeological and anthropological researches have taken place so far. (PNAS, 2014; doi: 10.1073 / pnas.1323666111)

(University of T bingen, 22.04.2014 - AKR)