A genome sequenced from a modern human skull has been dated to about 45,000 years old, making it the oldest discovery of its kind. It is an important archaeological find, but the use of an unconventional dating method leaves doubts about the result. In a related study, scientists also show that mixing between Neanderthals and humans was more common than we thought.
Modern people, also known as homo sapiens appeared some 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 like new Research Published today in Nature Ecology & Evolution reveals, scientists may have stumbled upon an even older genome. A team 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, if the dating method used can be considered reliable. The genome, drawn from a skull found in the Czech Republic, appears to be at least 45,000 years old and possibly even older.
A relative paper, also published today in Nature Ecology & Evolution, describes the remains of early modern humans found in a Bulgarian cave. The DNA of these people dates from roughly the same period and suggests that interbreeding with Neanderthals was probably more common than previously thought.
The skull described in the Prüfer document was taken from Koněprusy Cave in 1950 and was found alongside other skeletal remains. This cave is located in Zlatý kůň, which means “golden horse” in Czech, and it is only a 40 km drive from Prague.
G / O Media can receive a commission
Genetic analysis of the largely intact skull, which belonged to a human female, shows that she carried between 2% and 3% Neanderthal ancestry, essentially consistent with the amounts found in non-African people living today. That said, no human alive today descends directly from the Zlatý kůň woman, as she belonged to a population that did not pass any DNA on to the subsequent European or Asian populations of early modern humans.
“As far as we can tell, the population to which she belonged did not contribute to the current population,” explains Prüfer in an email. “We speculate that her people became extinct alongside the Neanderthals, who lived in Europe at the time, and that a major volcanic eruption in Italy that occurred about 39,000 years ago may have contributed to their demise.”
Prüfer refers to the Campanian Ignimbrite volcano eruption, which seriously disrupted the Northern Hemisphere’s climate, making life difficult for both modern humans and Neanderthals during the last European Ice Age.
This is all good and (fairly) uncontroversial – it’s not until we get to the dating of the skull that problems arise.
The first radiocarbon dating of the skull gave a date of nearly 15,000 years ago. Not believing this to be true (the skull’s anatomy suggested an older date), Prüfer and her colleagues tried again, resulting in a date closer to 27,000 years ago. After a few cleansing treatments, a third radiocarbon date was set, suggesting that the woman lived about 19,000 years ago. At this point, the scientists realized they were dealing with highly contaminated specimens.
“We found evidence of cow DNA contamination in the bone analyzed, suggesting that a bovine-based glue used in the past to [fix] the skull returned radiocarbon dates younger than the true age of the fossil, ”said Cosimo Posth, co-lead author of the study and professor of paleogenetics at the University of Tübingen, in a statement. Posth had previously worked as a research group leader at the Max Planck Institute.
Since radiocarbon dating had been ruled out as a useful tool for this specimen, the team turned to a technique where the length of DNA segments could be used to infer a person’s age. Specifically, the scientists measured the length of Neanderthal segments, as these segments become shorter with each successive generation.
This analysis suggests that the Zlatý kůň female lived at least 2,000 years after the last crossing involving her modern human and Neanderthal ancestors (approximately 63 to 78 generations). The “lengths of the Neanderthal segments are longer than those observed in the currently oldest modern human genome of the ~ 45,000-year-old Ust’-Ishim person from Siberia, suggesting that this person from Zlatý kůň is one of the earliest Eurasian inhabitants after the Expansion from Africa, ”the authors wrote in their study The Ust’-Ishim person was separated from the Neanderthals by about 84 to 94 generations, according to the paper.
Operating under the assumption of a single cross, the new results mean that Zlatý kůň is essentially the same age as the approximately 45,000-year-old Ust’-Ishim specimen, or possibly “up to a few hundred years older,” the paper said. But if a second Neanderthal mating event were to take place along the Ust’-Ishim line after this common Neanderthal mixing, then “Zlatý kůň could be even several thousand years older than Ust’-Ishim,” the authors wrote, adding that they have not. found support for a second Neanderthal mixture.
This is all very intriguing, but of course a firmer date should be set, hopefully through the use of other methods.
The authors “really don’t know how old the skull is, and the stated range 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 – are “interesting,” but he is not entirely sure about its effectiveness as a dating technique.
However, if these results are correct, the Zlatý kůň specimen now represents the oldest modern human genome in the fossil record. In addition, the new paper offers a rare glimpse into the genetic makeup of early modern European people dating back to this period.
The group to which the Zlatý kůň woman belonged did not survive, which is also interesting. It suggests multiple waves of migration from Africa to Europe, and / or some complex population replacement 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 their initial claim, “that the skull is very old, is correct.”
That modern humans lived in Europe so long ago is not a big deal. Evidence from 2020 suggests that modern humans were Gift in southeastern Europe between 47,000 and 43,000 years ago, while evidence from 2019 suggests some modern humans had this reached Europe, especially Greece, was already 210,000 years ago.
The second article, led by Mateja Hajdinjak of the Max Planck Institute for Evolutionary Anthropology in Leipzig, Germany, describes the remains of early modern humans found in the Bacho Kiro Cave in Bulgaria. These remains were initially described in the aforementioned 2020 paper, but the new analysis delves into their DNA.
Neanderthals and humans interbred somewhere between 55,000 and 60,000 years ago. Until now, however, archaeologists only had one person, one 40,000-year-old Oase1 fossil from Romania, who exhibited recent Neanderthal ancestry, in a finding that suggests that modern humans and Neanderthals have been bred on multiple occasions.
“However, we couldn’t rule out the possibility that this was just an accidental find,” Hajdinjak explains in an email. “Now, in this study, we have all three approximately 45,000-year-old individuals from the Bacho Kiro Cave with Neanderthal ancestors who are very close in their family history, just like Oase1,” she said, meaning that the “mixing was more common than us. previously thought. “
Indeed, the oldest three individuals found in Bacho Kiro carried between 3% and 3.8% Neanderthal DNA, which is slightly more than the current populations. Incredibly, these people had Neanderthal ancestors only six – or even fewer – generations back, in what is a truly amazing find.
“Contrary to what one would expect of ancient individuals in Europe, Bacho Kiro individuals are more closely related to human groups who contributed their genetic material to East Asians rather than West Eurasians,” said Hajdinjak. “Crucially, all the older Bacho Kiro Cave individuals have Neanderthal ancestors very closely in their pedigrees, suggesting that the admixture between these early humans in Europe and Neanderthals was common.”
Paleogenetics reveals some remarkable things about our past, especially when it interacts with both skeletal and archaeological artifacts. Our history is becoming increasingly visible and the view is only getting intriguing.