Our ancestors came to Europe around 45,000 years ago, but little is known about their fate and genetic affiliation. DNA analyzes of several early representatives of Homo sapiens, whose remains were found in the Czech Republic and Bulgaria, now provide more information. The genomes of both sites give evidence of earlier Neanderthal crossings. While parts of the early genetic material from Bulgaria can still be found in today’s Asians, the population of Homo sapiens women from the Czech Republic did not leave any genetic traces in today’s Eurasians.
The time 45,000 years ago brought great upheaval for Europe: The Neanderthals, who had lived in this region for thousands of years, disappeared and were replaced by our ancestors: representatives of Homo sapiens who immigrated from Africa to Eurasia via the Middle East. From the DNA analysis of modern Europeans and Asians we know that these first immigrants crossed several times with the last Neanderthals – that is why most of today’s Europeans still carry one to two percent Neanderthal DNA. But how the first Homo sapiens representatives were distributed on the Eurasian continent and how much their descendants contributed to today’s populations is unclear due to the lack of fossils. “So far, only three genomes have been isolated from individuals who lived close to the time when Europe and Asia were first settled more than 40,000 years ago,” explain Mateja Hajdinjak from the Max Planck Institute for Evolutionary Anthropology in Leipzig and her colleagues. These include an approximately 45,000 year old individual from the Siberian Ust’-Ishim, an approximately 40,000 year old find from China and the approximately 40,000 year old fossil “Oase 1” from Romania.
New DNA analyzes of several early representatives of Homo sapiens in Europe are now providing new insights into the beginnings of European human history. The finds are the remains of three individuals from the Bacho Kiro cave in Bulgaria and the skull of a woman from Zlaty kun in the Czech Republic. Two research teams – one headed by Hajdinjak and one headed by Kay Prüfer from the Max Planck Institute for the History of Man in Jena – have now genetically examined these fossils and partially re-dated them. The scientists paid particular attention to the proportion and length of Neanderthal gene sequences in the genome of these individuals, because this reveals when and how intensively the ancestors of these early Homo sapiens representatives crossed with Neanderthals. In addition, they compared the genome with that of modern Europeans and Asians as well as with that of the three already known early representatives of Homo sapiens in Eurasia.
Bacho Kiro: Neanderthal ancestors and Asian relatives
Analyzes of the finds from the Bach Kiro Cave confirmed that three of these individuals lived 45,930 to 42,580 years ago. This makes you one of the oldest known Europeans. The gene comparisons also showed that these early representatives of Homo sapiens in Europe carried between 3.0 and 3.8 percent Neanderthal DNA in their genome. From the length of the individual Neanderthal gene segments, the researchers conclude that the ancestors of all three individuals must have crossed with Neanderthals. These pairings were only six to seven generations ago, as Hajdinjak and her team report. “This suggests that the intermingling of Neanderthals and the first modern humans to arrive in Europe occurred more frequently than is often assumed,” the scientists said.
The DNA comparisons with other populations showed little agreement with characteristic gene segments of today’s Europeans: “The three individuals share more alleles with today’s populations from East Asia, Central Asia and the American continent than with populations from western Eurasia,” report Hajdinjak and her team . The early Homo sapiens find from China also shows similarities with the three examined genomes from Bulgaria. The researchers conclude that the immigrant population, to which the individuals from the Bacho Kiro cave belonged, reached Europe, but then moved on to Asia. Their descendants in Europe were ousted by representatives of Homo sapiens who later immigrated, and their genetic makeup disappeared from the European gene pool.
Zlaty kun: The oldest European?
The second research team led by Prüfer devoted its analyzes to the skull of a Homo sapiens woman from the Zlaty kun site in the Czech Republic. The age of this fossil was previously unclear because the stone tools found in the same cave cannot be assigned to any known cultural stage and radiocarbon dating produced contradicting results – the range ranged from 15,000 to 27,000 years. As the team has now found out, these relatively low age values can be attributed to subsequent contamination of the find: “We have found evidence of contamination with bovine DNA, which suggests that the skull parts were joined together with an animal-based adhesive in the past.” , explains co-author Cosimo Posth from the University of Tübingen. He and his colleagues found clues to the true age of this Homo sapiens woman in her genome. Because she also had remarkably long, uninterrupted sections of Neanderthal DNA in her genetic make-up. “Zlaty kun carries segments that are on average longer than those of all other Eurasian hunters and gatherers examined so far,” reports the team. The proportion of Neandertal DNA was also rather high at 3.2 percent.
From this, the researchers conclude that this woman must also come from the beginnings of the colonization of Eurasia by Homo sapiens. “Our results suggest that Zlaty kun is about the same age as the individual from Ust ‘Ishim, maybe even a few hundred years older,” write Prüfer and his colleagues. “Zlaty kun could thus be the oldest European human fossil with a preserved skull.” But unlike her genetically distinctly different almost contemporaries from the Bulgarian cave, no relationships between this woman and her population can be found with Europeans or Asians living today. According to the research team, this suggests that this early immigrant group did not seem able to establish itself in Europe.
“It is quite exciting that the earliest modern humans in Europe were ultimately unsuccessful,” says senior author Johannes Krause from the MPI for the History of Man. “As with Ust ‘Ishim and the skull from Oasis 1, Zlaty kun also shows no genetic continuity with modern humans who lived in Europe less than 40,000 years ago.” A possible, albeit very speculative, explanation for this failure According to the researchers, one of the first Homo sapiens immigration attempts could have been an eruption of the supervolcano under the Phlegraean Fields in Italy around 39,000 years ago. “This eruption strongly influenced the climate of the northern hemisphere and could have reduced the chances of survival of Neanderthals and early modern humans in large parts of western Eurasia,” the scientists speculate.
Source: Mateja Hajdinjak (Max Planck Institute for Evolutionary Anthropology, Leipzig) et al., Nature, doi: 10.1038 / s41586-021-03335-3; Kay Prüfer (Max Planck Institute for the History of Man, Jena) et al., Nature Ecology / & Evolution, doi: 10.1038 / s41559-021-01443-x