An international team of researchers has discovered and dated the remains of Homo sapiens and associated artifacts — including pendants manufactured from cave bear teeth that are reminiscent of those later produced by the last Neanderthals of western Europe — at the Initial Upper Paleolithic cave site of Bacho Kiro in Bulgaria. Published in two papers in the journal Nature and the journal Nature Ecology & Evolution, the findings add clarity to the arrival of Homo sapiens into Europe and to their interactions with the continent’s indigenous and declining Neanderthal population.
Bacho Kiro Cave is located 5 km west of Dryanovo, on the northern slope of the Balkan mountain range (Stara Planina) and about 70 km south of the Danube River.
The site formed at the mouth of a large karstic system and its deposits encompass late Middle Paleolithic and early Upper Paleolithic occupations.
Bacho Kiro Cave was excavated by the archaeologist D. Garrod in 1938, but is best known from more extensive excavations in the 1970s by a team and archaeologists led by B. Ginter and J. Kozłowski. The excavations in the 1970s yielded fragmentary human remains that were subsequently lost.
In 2015, a research team led by archaeologists from the National Archaeological Institute of Bulgaria and the Max Planck Institute for Evolutionary Anthropology resumed work at Bacho Kiro Cave with the goals of clarifying the chronology and the biological nature of the makers of the artifacts.
The researchers uncovered thousands of animal bones, stone and bone tools, beads and pendants and the remains of five human individuals.
“The animal remains from the site illustrate a mix of cold and warm adapted species, with bison and red deer most frequent. These were butchered extensively but were also used as a raw material source,” said team member Dr. Rosen Spasov, a paleontologist at New Bulgarian University.
“The most remarkable aspect of the faunal assemblage is the extensive collection of bone tools and personal ornaments,” added Dr. Geoff Smith, a zooarchaeologist at the Max Planck Institute for Evolutionary Anthropology.
“Cave bear teeth were made into pendants, some of which are strikingly similar to ornaments later made by Neanderthals in western Europe.”
The scientists then examined teeth and bones from Bacho Kiro Cave to ascertain which species occupied the site.
Using a state-of-the-art technology called Zooarchaeology by Mass Spectrometry (ZooMS), they identified human bone fragments and concluded that they were at least 45,000 years old — a period coinciding with the arrival of multiple waves of Homo sapiens into Europe.
Subsequent shape analyses of the tooth and DNA examination of the fragments determined that they belonged to Homo sapiens and not Neanderthals, whose presence was not evident among the discovered fossils.
“ZooMS allows us to identify previously unidentifiable bone fragments as some form of human,” said team member Professor Shara Bailey, a researcher in the Department of Anthropology at New York University and the Department of Human Evolution at the Max Planck Institute for Evolutionary Anthropology.
“From there, we can apply more sophisticated techniques to identify the species and more accurately date human bones.”
“Given the exceptionally good DNA preservation in the molar and the hominin fragments identified by protein mass spectrometry, we were able to reconstruct full mitochondrial genomes from six out of seven specimens and attribute the recovered mitochondrial DNA (mtDNA) sequences from all seven specimens to modern humans,” said team member Dr. Mateja Hajdinjak, a postdoctoral researcher at the Francis Crick Institute and the Max Planck Institute for Evolutionary Anthropology.
“Interestingly, when relating these mtDNAs to those of other ancient and modern humans, the mtDNA sequences from Layer I fall close to the base of three main macrohaplogroups of present-day people living outside of Sub-Saharan Africa. Furthermore, their genetic dates align almost perfectly with those obtained by radiocarbon.”
“The Bacho Kiro Cave site provides evidence for the first dispersal of Homo sapiens across the mid-latitudes of Eurasia,” said team co-leader Dr. Jean-Jacques Hublin, director at the Max Planck Institute for Evolutionary Anthropology.
“Pioneer groups brought new behaviors into Europe and interacted with local Neanderthals.”
“This early wave largely predates that which led to their final extinction in western Europe 8,000 years later.”
“Our findings link the expansion of what were then advanced technologies, such as blade tools and pendants made from teeth and bone, with the spread of Homo sapiens more than 45,000 years ago,” Professor Bailey said.
“This confirms that Homo sapiens were mostly responsible for these ‘modern’ creations and that similarities between these and other sites in which Neanderthals made similar things are due to interaction between the populations.”
J. Hublin et al. Initial Upper Palaeolithic Homo sapiens from Bacho Kiro Cave, Bulgaria. Nature, published online May 11, 2020; doi: 10.1038/s41586-020-2259-z
H. Fewlass et al. A 14C chronology for the Middle to Upper Palaeolithic transition at Bacho Kiro Cave, Bulgaria. Nat Ecol Evol, published online May 11, 2020; doi: 10.1038/s41559-020-1136-3
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