A genome sequenced from a modern human skull has been dated to be approximately 45,000 years old, making it the oldest such discovery. This is a significant archaeological discovery, but the use of an unconventional dating method leaves the result in doubt. In a related study, scientists also show that the mix between Neanderthals and humans occurred more often than we thought.
Modern humans, also known as homo sapiens, emerged about 300,000 years ago in Africa. There are skeletal remains of our distant ancestors, but the fossil record is poor. Even poorer is the genetic evidence, the oldest of which is the genome of a 45,000-year-old Ust’-Ishim person from western Siberia, described in 2014.
But as a novelty research published today in Nature Ecology & Evolution reveals that scientists may have come across an even older genome. A team co-led by Kay Prüfer of the Max Planck Institute for the Science of Human History in Germany has discovered what may be the oldest reconstructed modern human genome in the fossil record. That is, whether the dating method used can be considered reliable. The genome, extracted from a skull found in the Czech Republic, appears to be at least 45,000 years old and possibly even older.
A related paper, also available today in Nature Ecology & Evolution, describes the remains of the first modern humans found in a Bulgarian cave. The DNA of these people, dating back to the same time period, suggests that interbreeding with Neanderthals was probably more frequent than previously assumed.
The skull described in the document Prüfer was removed from the Koněprusy cave in 1950 and found next to other skeletal remains. This cave is located in Zlatý kůň, which means “golden horse” in Czech, and is 40 kilometers from Prague.
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Genetic analysis of the skull, mostly intact, which belonged to a human female, shows that it carried between 2% and 3% Neanderthal ancestry, which basically matches the amounts found in non-African people currently living. That said, no human being currently living is a direct descendant of the woman Zlatý kůň, as she belonged to a population that did not transmit any DNA to later European or Asian populations of early modern humans.
“As far as we know, the population to which it belonged did not contribute to the current populations,” Prüfer explained in an email. “We speculate that its people became extinct alongside the Neanderthals, who were living in Europe at the time, and that a large volcanic eruption in Italy that occurred about 39,000 years ago may have contributed to its extinction.”
Prüfer refers to the Campanian ignimbrite volcanic eruption, which severely altered the climate of the northern hemisphere, making life difficult for both modern humans and Neanderthals during the last European ice age.
All of this is good and (reasonably) uncontroversial: that’s when we get to the skull dating when problems arise.
The initial dating of the skull with radiocarbon produced a date close to 15,000 years. Prüfer and his colleagues, who did not believe this to be true (the anatomy of the skull suggested an earlier date), tried again, which resulted in a date closer to 27,000 years ago. After some cleaning treatments, a third radiocarbon date was determined, suggesting that the woman lived about 19,000 years ago. It was at this time that scientists realized that they were dealing with highly contaminated specimens.
“We found evidence of cow DNA contamination in the analyzed bone, suggesting that a bovine-based glue used in the past by [fix] the skull returned radiocarbon dates younger than the actual age of the fossil, ”Cosimo Posth, co-author of the study and professor of paleogenetics at the University of Tübingen, said in a statement. Posth had previously worked as a research group leader at the Max Planck Institute.
With radiocarbon dating discarded as a useful tool for this specimen, the team resorted to a technique in which the length of DNA segments can be used to infer a person’s age. Specifically, scientists measured the length of Neanderthal segments, as these segments shrink with each successive generation.
This analysis suggests that the woman Zlatý kůň lived at least 2,000 years after the last interbreeding event involving her modern human and Neanderthal ancestors (approximately 63 to 78 generations). The “lengths of Neanderthal segments are longer than those observed in the oldest modern human genome of the Ust’-Ishim individual of Siberia, ~ 45,000 years old, which suggests that this individual from Zlatý kůň is one of the first Eurasian inhabitants to they continue to expand outside Africa, ”the authors wrote in their study. According to the newspaper, the Ust’-Ishim person was separated from the Neanderthals by 84 to 94 generations.
Working under the assumption of a single cross-breeding event, the new results mean that Zlatý kůň is basically the same age as the Ust’-Ishim specimen of about 45,000 years ago, or possibly “up to a few hundred years ”, According to the paper. But if a second Neanderthal interbreeding event took place along the Ust’-Ishim lineage after this common Neanderthal mix, then “Zlatý kůň could be even several thousand years older than Ust’-Ishim,” they said. writing the authors, adding that they have not found support for a second Neanderthal mix.
All of this is very intriguing, but it is clear that a firmer date needs to be set, hopefully, by using other methods.
The authors “don’t really know how old the skull is and the range offered is wide,” Israel Hershkovitz, an archaeologist at Tel Aviv University and an expert on early modern humans, said in an email. That said, Hershkovitz said the data used to determine the age of the skull (mitochondrial DNA and the pattern of Neanderthal gene segments) is “interesting,” but he is not entirely sure of its effectiveness as a technique. dating.
If these results are accurate, however, the Zlatý kůň specimen now represents the oldest modern human genome in the fossil record. In addition, the new article provides a rare insight into the genetic composition of the first modern European humans dating back to this time period.
The group to which the woman Zlatý kůň belonged did not survive, which is also interesting. It suggests multiple waves of migration to Europe from Africa and / or some complex population substitution scenarios, in which some groups survived and others did not. That this specimen belonged to “a population prior to the division between European and Asian populations” is significant, Hershkovitz said, provided his first statement, “that the skull is very old, is correct.”
That modern humans lived in Europe a long time ago is not an important stretch. The evidence for 2020 suggests that modern humans were present in southeastern Europe between 47,000 and 43,000 years ago, while 2019 evidence suggests that some modern humans had achieved Europe, specifically Greece, until 210,000 years ago.
The second paper, directed by Mateja Hajdinjak of the Max Planck Institute for Evolutionary Anthropology in Leipzig, Germany, describes the remains of the first modern humans found in the Bacho Kiro Cave in Bulgaria. These remains were initially described in the said document from 2020, but the new analysis delves into its DNA.
Neanderthals and humans crossed at some point between 55,000 and 60,000 years ago. Until now, however, archaeologists had only one person, a 40,000-year-old Oase1 fossil from Romania, which exhibited recent Neanderthal ancestry, in a finding that suggests modern and Neanderthal humans bred on multiple occasions.
“However, we could not rule out that this was just a chance find,” Hajdinjak explained in an email. “Now in this study, we have the three individuals from Bacho Kiro’s cave with Neanderthal ancestors very close to their family history, about 45,000 years old, just like Oase1,” he said, meaning that “the mix was more common to what we thought above. “
In fact, the three oldest individuals found in Bacho Kiro carried between 3% and 3.8% Neanderthal DNA, slightly more than current populations. Incredibly, these people had Neanderthal ancestors just six (or even fewer) generations ago, in what is a truly amazing find.
“Contrary to what might be expected of ancient individuals in Europe, Bacho Kiro’s individuals are more related to human groups that contributed their genetic material to East Asians rather than Western Eurasians,” Hajdinjak said. “It is crucial that all the older individuals in Bacho Kiro Cave have Neanderthal ancestors very close in their family trees, suggesting that mixing between these early humans in Europe and Neanderthals was common.”
Paleogenetics reveals some remarkable things about our past, especially when it works in conjunction with skeletal and archaeological artifacts. Our story is getting more and more focused and the vision just gets more intriguing.