The skull of a modern human female individual from Zlatý kůň.Credit: Marek Jantač
Scientists have the oldest order Homo sapiens DNA on record, showing that many of the first humans in Europe had Neanderthals in their pedigrees. Yet these individuals are not related to later Europeans, according to two genome studies of remains dating back more than 45,000 years from caves in Bulgaria and the Czech Republic.1,2.
The research contributes to increasing evidence that modern humans regularly mixed with Neanderthals and other extinct family members, says Viviane Slon, a paleogeneticist at Tel Aviv University in Israel. “It’s different times, different places and it happens again and again.”
The genetic history of the earliest humans in Europe and Asia has been blurred. Although researchers sequenced DNA from Neanderthal humans and other extinct family members as young as 430,000 years old, there is a scarcity of genetic information from the period between 47,000 and 40,000 years ago, known as the Initial Upper Paleolithic, and no Homo sapiens DNA at all from before this period. Genomes of people from Siberia and Romania showed no connection to later waves of Europeans, but a 40,000-year-old individual from China is a partial ancestor of modern East Asian people.
Like all modern-day people of non-African descent, these early Eurasians carried Neanderthal DNA. Researchers thought that this was probably due to mixing between the groups in the Middle East 50,000–60,000 years ago. But a 2015 study3 of the genome of the 40,000-year-old Romanian individual, from a website called Peștera cu Oasis, had a surprise: an ancestor of the Neanderthal in the last four to six generations, indicating that people in Europe also have Neanderthal people intervened.
From the genome of the Oasis man it is not clear whether it is common in Europe. He lived in the time when Neanderthal population, which was already sparse, began to disappear from the region.
Genetic mixture
The latest genome studies, both published on April 7, explain the relationships between the first modern people of Europe, later Homo sapiens and Neanderthals, but also throws up some new questions. A study, in Nature1, is based on a tooth and fragmentary remains of the Bacho Kiro Cave in Bulgaria; the other, in Natural ecology and evolution2, look at an almost complete skull from a cave known as Zlatý kůň in the Czech Republic.
The three oldest Bacho Kiro individuals, dated between 45,900 and 42,600 years old, all had recent Neanderthal ancestors, reports a team led by molecular biologist Mateja Hajdinjak and evolutionary geneticist Svante Pääbo, both at the Max Planck Institute for Evolutionary Anthropology (MPI – EVA) in Leipzig, Germany. The genomes of modern non-Africans usually contain about 2% Neanderthal ancestry, but the Bacho Kiro individuals had slightly more: 3.4-3.8%, and the chromosome segments – which shorten in successive generations – were significantly longer.
By measuring these segments, the researchers estimated that the Bacho Kiro individuals had Neanderthal ancestors as recently as the last six or seven generations – and probably in Europe, not in the Middle East. ‘We’ve seen these great pieces. It was absolutely incredible, ”said Hajdinjak, who is now at the Francis Crick Institute in London and was part of the team that identified the same patterns in the oasis man’s genome. “What’s the chance of finding it again?”
The Neanderthal lineage of the Zlatý kůň woman extends considerably further: 70–80 generations, or perhaps 2000–3,000 years, says Johannes Krause, a paleogeneticist at the MPI – EVA, who led the study. His team could not date the skull accurately due to the contamination. But based on his Neanderthal ancestry, Krause suspects he is more than 45,000 years old, and in the same ballpark as the oldest remains of Bacho Kiro. “We now have some of the oldest human genomes out there,” Hajdinjak adds.
The detection of the sex line
The oldest individuals of Bacho Kiro and the Zlatý kůň woman are not related to later Europeans, old or modern, which means that their generation must disappear from the region. But to their surprise, Hajdinjak and her colleagues found that the Bacho Kiro people shared a connection with contemporary East Asians and Native Americans. Hajdinjak suggests that the Bacho Kiro remains represent a population that once lived in Eurasia but disappeared from Europe and lived in Asia.
The fact that several people from Bacho Kiro had many recent relatives from Neanderthal indicates that the groups regularly mixed in Europe, says Marie Soressi, an archaeologist at Leiden University in the Netherlands who plans to study European archeology through to examine this lens.
Stone tools and other artifacts common to the Early Upper Paleolithic – and unlike typical Neanderthals and later human tools – could be a product of cultural exchanges or even mixed populations, she says. “We really want to better understand what happened, what the historical process was and how peaceful the encounters were.”