A team from the Max Planck Institute for Evolutionary Anthropology conducts excavations at Bacho Kiro Cave in 2021, as part of a recent research on the climate conditions faced by early humans in Europe. Credit: MPI-EVA/ Tsenka Tsanova.
Analysis of genomic data and archaeological records has added to the picture of how Europe and Asia were populated by Homo sapiens coming from Africa. Scientists have found evidence of several migration waves in different directions, during which the ancestors of modern East Asians initially populated Western Europe, before being replaced by another population.
Anatomically modern humans left Africa on several occasions, from 215,000 years ago to more recent migrations that happened between 70,000 and 60,000 years ago. The prevailing view is that, about 45,000-40,000 years ago, this wave of movement from Africa diverged in some region between Africa and Europe, originating what we now call European and East Asian populations.
But this picture was complicated by the recent discovery in Bacho Kiro, Bulgaria, of the 45,000 years-old remains of individuals who are genetically closer to the ancient East Asian population than to the European one. This suggests that the two branches did not clearly split by migrating towards separate locations at the same time. In a study published in Genome Biology and Evolution, researchers from the universities of Padova and Bologna looked for a plausible explanation to these population dynamics1.
“Geneticists teamed up with archaeologists in a single joint study, rather than working in different teams with their own papers,” says author Luca Pagani from Università di Padova. “A multidisciplinary approach to such complex biocultural events is incredibly valuable”. Computational and statistical methods are widely employed to reconstruct multiple lineage trees that may fit with available genetic data. In this case, scientists used material evidence from Palaeolithic populations in Europe as an additional criterion for selecting between lineage trees that were equally fitting with genetic data. “Of the several possible ancestry models that could accommodate the genetic evidence, we selected the one with a good fit to the data” says first author, Leonardo Vallini, from Università di Padova.
According to the conclusions, rather than a clear East/West geographical bifurcation, there were several waves of migration. During the first, that took place around 45,000 years ago, populations that would later become prevalent in East Asia colonised Europe, and encountered Neanderthals with which they bred before leaving for the East. This would explain the presence of individuals in Bacho Kiro with genomes related to that of modern East Asian populations.
In a subsequent wave, populations more closely related to modern Europeans colonised Europe, breeding with the previous native populations that still retained genetic traces of the Neanderthal population and the ‘East Asian’ wave. This could also explain the sudden appearance of new stone-cutting techniques not were yet spread in Western Europe.
According to Marco Peresani, an anthropologist at Università di Ferrara, who was not involved in the study, “despite the difficulties in the attribution of genetic samples to Palaeolithic cultures, the conclusion suggested by the study is really interesting”. The authors hope that future studies with paleoclimatological data and genome samples from the Indian subcontinent could further clarify the sequence of migration waves into Eurasia.
