NEW YORK – Teams led by investigators at the Max Planck Institute for the Science of Human History have identified now-extinct modern humans that belong to genetic lineages that are distinct from those described in the past.
For a study published in Nature Ecology and Evolution on Wednesday, researchers at Max Planck and other centers in Europe presented findings from genome sequencing analysis of ancient remains from a woman dubbed the Zlatý kůň individual, whose skull was found in a Czechian cave in 1950.
Using a combination of targeted enrichment sequencing and shotgun sequencing, they generated genome-wide SNP data that made it possible to compare Zlatý kůň to other present-day and ancient individuals, including 45,000-year-old sequences from the Ust'-Ihsam individual, the oldest modern human sequenced so far. Together, these and other data suggested the woman belonged to a genetic lineage that did not contribute ancestry to present-day populations in Europe or Asia.
"It seems that she belonged to a group of people that are not closer to any particular out-of-African population," co-first author Kay Prüfer, a researcher affiliated with the Max Planck Institute for the Science of Human History and the Max Planck Institute for Evolutionary Anthropology, explained in an email.
Though it remains unclear why this modern human lineage disappeared, he and his colleagues speculated that they may have been victims to the climactic fall out that wiped out some early modern human and Neanderthal populations following a volcanic eruption in Italy around 39,000 years ago.
The proportion of Neanderthal ancestry detected in the Zlatý kůň genome was on par with that found in other ancient hunter-gatherer populations, the team reported. But the continuous Neanderthal sequences tended to be longer than those found in other ancient modern humans, eclipsing those found in the Ust'-Isham individual.
Although the sample appeared to be contaminated and difficult to date with conventional approaches, the researchers noted that collagen sequences put the individual at at least 34,000 years old, while insights from the admixed Neanderthal sequences suggest she died much earlier.
"Assuming a common Neanderthal admixture event, these results suggest that Zlatý kůň is of approximately the same age as the [approximately] 45,000-year-old Ust'-Isham individual or up to a few hundred years older," Prüfer and his co-authors wrote, noting that the current results "could make Zlatý kůň the oldest European individual with a largely preserved skull."
In a related paper in Nature on Wednesday, Max Planck's Svante Pääbo and colleagues shared findings from a genome-wide sequence study focused on three ancient individuals from an excavated cave in Bulgaria, whose remains appeared to be span around 42,600 to 45,900 years old.
The Bulgarian individuals, who the authors called "the earliest Late Pleistocene modern humans known to have been recovered in Europe so far," came from a site with artefacts linked to an Initial Upper Paleolithic population.
Based on genome-wide SNP profiles gleaned from sequences for half a dozen specimens collected from the cave, the team uncovered alleles that are shared with those found in some current populations in East Asia, Central Asia, and the Americas, with fewer shared alleles turning up in populations found in western Eurasia today.
Again, the Neanderthal sequences documented in the ancient Bulgarian individuals appeared to be relatively long, the researchers reported, and pointed to even more recent Neanderthal mixing than that found in the Zlatý kůň individual — likely within the just six or seven generations.
More broadly, data from that set of ancient genomes suggested that "several distinct modern human populations existed during the early Upper Paleolithic in Eurasia."
Together with findings from his team's study of the Zlatý kůň individual, Prüfer said results generated from the Bulgarian remains hint that at least two modern human populations inhabited Europe in the time before 45,000 years ago. He noted that "we'll need more analysis to figure out how and if they are in any way related."