Archaeology

Bacho Kiro Cave Reveals Volumes About Human-Neanderthal Relationship

In 2020 a team of researchers reported the discovery of a collection of Upper Palaeolithic stone tools at the Bacho Kiro Cave site in Bulgaria. Among the tools they discovered the remains of modern humans that radiocarbon dated to between 43,000 and 46,000 years old. Now, after careful analysis of the bones, the researchers have published that they represent “the earliest known dispersal of modern humans across the mid-latitudes of Eurasia.”

The Bacho Kiro Cave site contains a spectacular collection of tunnels and shafts making up one of the most important tourist sites in Bulgaria. (Nenko Lazarov / CC BY 2.5)

The Bacho Kiro Cave site contains a spectacular collection of tunnels and shafts making up one of the most important tourist sites in Bulgaria. (Nenko Lazarov / CC BY 2.5 )

Oldest Remains of Modern Humans Found in Bacho Kiro Cave

The team of archaeologists was led by Dr. Mateja Hajdinjak and it was composed with a multi-disciplinary team of researchers from the Bulgarian National Institute of Archaeology, the Academy of Sciences, and the Max Planck Institute for Evolutionary Anthropology in Germany. According to Science Daily , their study of the human bones dating to 45,000 years ago in Bacho Kiro Cave, Bulgaria, led the team researchers to conclude that they are “the oldest securely dated remains of modern humans in Europe.”

The skull of a modern human female individual from Zlatý kůň (Marek Jantač / Nature)

The skull of a modern human female individual from Zlatý kůň (Marek Jantač / Nature)

A comparison of the genomes with those of people who lived later in Europe and in Asia showed that this early human group of hunters in Europe “contributed genes to later people, particularly present-day East Asians.” Large stretches of Neanderthal DNA was also identified in the genomes of the Bacho Kiro Cave bones which means the modern humans had Neanderthal ancestry going back only about about five to seven generations. The scientists say that this particular finding suggests when the first modern humans arrived in Europe, inbreeding with Neanderthals was “the rule rather than the exception.”

Image of second lower molar of a modern human discovered at the Bacho Kiro Cave in Bulgaria. DNA analysis has concluded he had a Neandertal ancestor less than six generations before he lived. (MPI-EVA - Rosen Spasov / Max Plank Institute)

Image of second lower molar of a modern human discovered at the Bacho Kiro Cave in Bulgaria. DNA analysis has concluded he had a Neandertal ancestor less than six generations before he lived. (MPI-EVA – Rosen Spasov / Max Plank Institute )

DNA at Bacho Kiro Cave Indicates Social Upheaval

Published in Nature, the new paper shows that the 45,000-year-old Bacho Kiro Cave people contributed genes to present-day people. “Surprisingly,” wrote the scientists, the bulk of these genes are to be found in modern day East Asia, and the Americas, while it was expected that these genes would be found in populations closer to where they lived, at the Bacho Kiro Cave in Europe.

Another skeleton was discovered in Bacho Kiro Cave dating to 35,000-year-ago, that was not related to the earlier people, and the researchers went so far as to say this person was “genetically distinct” from the cave’s earlier inhabitants. The scientists concluded that this genetic difference demonstrated the earliest history of modern humans in Europe “may have been tumultuous and involved population replacements.” One can only imagine that over 10,0000 years the population at any one cave would see hundreds of total overhauls.

Switching Alliances in the Deeply-Ancient World

All of the studies that have been done over the last decade looking at the ancient genes of modern humans living in Eurasia, have demonstrated that they “all” have recent Neanderthal ancestors. But the earliest people at Bacho Kiro Cave lived at a time when Neanderthals were still in existence and therefore their DNA, and genome maps, are supremely important to archaeologists and anthropologists. These samples hold relatively “fresh” Neanderthal DNA, for want of a better term.

The paper says the team of researchers found that the Bacho Kiro Cave individuals had “higher levels of Neanderthal ancestry than nearly all other early humans,” with the exception of one 40,000-year-old skeleton discovered in Romania. Furthermore, almost all of the DNA observed was in “extremely long stretches” which shows these individuals had Neanderthal ancestors only five to seven generations back in their family trees” writes Dr. Mateja Hajdinjak.

The paper concludes by suggesting that the first modern humans arriving in Eurasia “frequently mixed” with Neanderthals. And if all these findings were not enough, the team went so far as to speculate that some humans may even have “become absorbed into resident Neanderthal populations.”

Just imagine for a second living 45,000-years-ago in a hunting community based in a cave in central Europe. What on Earth could have happened to inspire some humans to up sticks and leave everything they know, family and home (cave), to unite with a band of hunters from another species? Shortly after these interactions, this species would vanish into time, leaving us as the “winners” on the Planet of the Apes.

Top image: Excavations at the Bacho Kiro Cave have shown that modern humans frequently interbred with Neanderthals. The image shows excavations in 2016. Source: Željko Režek / Max Plank Institute

By Ashley Cowie


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