‘Earliest Dispersal of Modern Humans’ in Eurasia’s Mid-Latitudes, Regular Mixing with Neanderthals Revealed by 46,000-Year-Old Remains from Bulgaria’s Bacho Kiro Cave

‘Earliest Dispersal of Modern Humans’ in Eurasia’s Mid-Latitudes, Regular Mixing with Neanderthals Revealed by 46,000-Year-Old Remains from Bulgaria’s Bacho Kiro Cave

A photo showing a researcher registering newly discovered artifacts in the Bacho Kiro Cave from the Initial Upper Paleolithic, from Layer 1 of Niche 1. Digs in the Main Section are visible in the background. Photo: Zeljko Rezek, Max Planck Institute of Evolutionary Anthropology, Leipzig, via the National Institute and Museum of Archaeology, Sofia.

An international team of scientists has arrived at crucial conclusions about the earliest spreading of modern humans throughout Eurasia and the Americas and about their mixing with Neanderthals in the Upper Paleolithic based on years of research of human remains and tools from 43,000 – 46,000 years ago discovered in the Bacho Kiro Cave near the town of Dryanovo in Central Bulgaria.

The Bacho Kiro Cave near Dryanovo is a well-known cultural tourism site not only because of archaeological research there but also because of its miraculous karst formations, and the fact that back in 1937 it became the first cave in Bulgaria equipped for tourist visits.

The archaeological excavations in the Bacho Kiro Cave, which contains some of the oldest remains of Homo sapiens in Europe, already indicated the archaeological site demonstrated the transition from the Middle Paleolithic (Middle “Old Stone Age” – 300,000 – 50,000/30,000 years Before Present) to the Upper (Late) Paleothic (Late “Old Stone Age” – 50,000 – 12,000 years Before Present).

However, the latest conclusions based on the years of international scientific research of the discoveries in Bulgaria’s Bacho Kiro Cave come from genetic research of the Paleolithic human remains from it, including scanning their genomes for Neandertal DNA.

The international research project for the Bacho Kiro Cave by scientists from the the Max Planck Institute for Evolutionary Anthropology, Germany, and the National Institute and Museum of Archaeology of the Bulgarian Academy of Sciences has focused on remains of modern human remains “discovered in direct association with the Initial Upper Palaeolithic stone tools” found inside the cave.

The earliest remains of modern humans found in Bulgaria’s Bacho Kiro cave were directly radiocarbon dated to between 43,000 and 46,000 years ago, announce the Max Planck Institute for Evolutionary Anthropology in Leipzig and the National Institute and Museum of Archaeology in Sofia, following the release of paper on the discoveries published in the Nature Journal.

The entrance of the Bacho Kiro Cave near Dryanovo in Central Bulgaria, whose passageways have a combined total length of about 3 kilometers. The archaeological excavations have been conducted in a cave hall to the left of the entrance. Photo: Nikolay Zahariev, New Bulgarian University via National Institute and Museum of Archaeology, Sofia

“They are thus the earliest known dispersal of modern humans across the mid-latitudes of Eurasia,” state the scientific institutions, revealing details about the genetic research of a team led by Mateja Hajdinjak.

“[The team] have now sequenced the genomes of five individuals found at the Bacho Kiro Cave. Four individuals are between 43,000-46,000-years-old and were found together with stone tools belonging to the Initial Upper Palaeolithic, the earliest culture associated with modern humans in Eurasia,“ the international group of researchers says.

They add that the remains of an additional individual from Bulgaria’s Bacho Kiro Cave have been established to be “around 35,000-years-old and found with stone tools of a later type.”

“It was previously thought that bearers of the Initial Upper Palaeolithic died out without contributing genetically to modern humans arriving later. However, the researchers now show that the oldest Bacho Kiro Cave individuals, or groups closely related to them, contributed genes to present-day people,“ the researchers point out.

“Surprisingly, this contribution is found particularly in East Asia and the Americas rather than in Europe where the Bacho Kiro Cave people lived,” they note.

A photo showing the excavations of the Niche 1 (left) and the Main Section (right) of the Bacho Kiro Cave by the Bulgarian-German research institutions’ team between 2016 and 2019. A cement surface visible in the foreground is a spot excavated by a Bulgarian – Polish team back in 1971 – 1975. Photo: Nikolay Zahariev, New Bulgarian University via National Institute and Museum of Archaeology, Sofia

A photo showing excavations of Layer 1 from the Initial Upper Paleolithic in the Bacho Kiro Cave in Central Bulgaria. The pictured spot yielded four bone fragments from modern humans, a wide range of bone and stone tools, and cave bear teeth pendants. Photo: Tsenka Tsanova, Max Planck Institute of Evolutionary Anthropology, Leipzig, via the National Institute and Museum of Archaeology, Sofia

The scholars declare further that these genetic links to Asia mirror the links seen between the Initial Upper Palaeolithic stone tools and personal ornaments found in Bacho Kiro Cave and tools and ancient jewelry found across Eurasia to Mongolia.

The genetic research has demonstrated that the “later” individual found in Bacho Kiro Cave whose remains are about 35,000 years old belonged to a group that was genetically distinct from the earlier inhabitants of the cave.

“This shows that the earliest history of modern humans in Europe may have been tumultuous and involved population replacements,” state the scientists from the Max Planck Institute for Evolutionary Anthropology in Leipzig and the National Institute and Museum of Archaeology in Sofia.

A lower molar of a modern human, Homo sapiens, discovered in the Main Section of the Bacho Kiro Cave alongside tools from Initial Upper Paleolithic. Genetic research has now shown that the person in question had a Neanderthal ancestor fewer than six generations earlier. A bone fragment from the same individual was discovered in Layer 1 of Niche 1 of the cave. Photo: Rosen Spasov, New Bulgarian University via National Institute and Museum of Archaeology, Sofia

A lower molar of a modern human, Homo sapiens, discovered in the Main Section of the Bacho Kiro Cave alongside tools from Initial Upper Paleolithic. Genetic research has now shown that the person in question had a Neanderthal ancestor fewer than six generations earlier. A bone fragment from the same individual was discovered in Layer 1 of Niche 1 of the cave. Photo: Rosen Spasov, New Bulgarian University via National Institute and Museum of Archaeology, Sofia

It is emphasized that the earliest Paleolithic inhabitants of the Bacho Kiro Cave in today’s Central Bulgaria lived at a time when Neandertals were still around. This led the researchers to scan their genomes for fragments of Neandertal DNA.

They have thus concluded that there was a great deal of mixing, and very recent at that, between the early modern humans and the Neanderthals

“We found that the Bacho Kiro Cave individuals had higher levels of Neandertal ancestry than nearly all other early humans, with the exception of a ~40,000-year-old individual from Romania,” says lead author Mateja Hajdinjak.

“Crucially, most of this Neandertal DNA comes in extremely long stretches. This shows that these individuals had Neandertal ancestors some 5 to 7 generations back in their family trees,” she elaborates.

The institutions note that while only a handful of genomes from modern humans who lived at the same time in Eurasia as some of the last Neandertals have been recovered, nearly all of them have recent Neandertal ancestors.

A graph showing long sequences of Neanderthal DNA identified in the genome of an early modern human who lived about 43,000 years ago, during the Initial Upper Paleolithic, in the Bacho Kiro Cave. The sequences indicate the person in question had a Neanderthal ancestor fewer than six generations earlier. Graph: Mateja Hajdinjak, Petra Korlević Max Planck Institute of Evolutionary Anthropology, Leipzig, via the National Institute and Museum of Archaeology, Sofia

The findings from the Paleolithic remains in Bulgaria’s Bacho Kiro Cave have contributed towards a conclusion that before modern humans arrived in large enough numbers in Eurasia to replace the Neanderthals, it was Neanderthal groups that may have actually assimilated early modern human arrivals.

“The results suggest that the first modern humans that arrived in Eurasia mixed frequently with Neandertals. They may even have become absorbed into resident Neandertal populations. Only later on did larger modern human groups arrive and replace the Neandertals,” says Svante Pääbo, who coordinated the genetic research.

The finds from the years of research of the Paleolithic materials from the Bacho Kire near Bulgaria’s Dryanovo are also construed as demonstrating the importance of the Balkan Peninsula in the contract between the Neanderthals and the early modern humans.

“The paleogenetic results from Bacho Kiro Cave demonstrate that the Balkans are key region for investigating early modern human migrations and interactions with local Neanderthals,” says Tsenka Tsanova, one of the lead archaeologists of the excavations in the cave and an expert in lithic technologies.

“These new data also help link these early modern humans in Europe to Initial Upper Paleolithic material culture known from Palaeolithic sites across the mid-latitude of Eurasia as far east as Mongolia,” she elaborates.

One of the excavation directors, Tsenka Tsanova of the Department of Human Evolution at the Max Planck Institute for Evolutionary Anthropology (Leipzig, Germany), taking sediment samples for DNA analysis. Photo: Nikolay Zahariev, MPI-EVA Leipzig, License: CC-BY-SA 2.0

Personal ornaments and bone tools from Bacho Kiro Cave (left) and from Grotte du Renne (France, right). The Bacho Kiro Cave artifacts are attributed to Homo sapiens and date to approximately 45,000 years ago. The Grotte du Renne artifacts are attributed to Neandertals and are not quite as old. Photo: Rosen Spasov and Geoff Smith, MPI-EVA Leipzig, License: CC-BY-SA 2.0

Stone artifacts from the Initial Upper Paleolithic at Bacho Kiro Cave. 1-3, 5-7: Pointed blades and fragments from Layer I; 4: Sandstone bead with morphology similar to bone beads; 8: The longest complete blade. Photo: Tsenka Tsanova, MPI-EVA Leipzig, License: CC-BY-SA 2.0

The results from the Bacho Kiro Cave research mean that the human remains and tools from Initial Upper Paleolithic period found in it show its inhabitants differed from and predated the Aurignacian Culture of Upper Paleolithic European early modern humans, which existed between 43,000 years ago and 26,000 years ago.

“The recently discovered modern human remains in Bulgaria, in the Bacho Kiro cave near the town of Dryanovo, dating from 43,000 – 46,000 years ago, are undoubtedly one of the most ancient modern people discovered in Europe,” say Nikolay Sirakov and Svoboda Sirakova, leaders from the Bulgarian side of the Bulgarian-German research project of Bacho Kiro Cave.

“They were found together with an archeological assemblage from the Initial Upper Paleolithic, which differs from the Aurignacian culture and definitely precedes its appearance,” the researchers emphasize.

Sirakov, a long-time renowned researcher of Prehistory, has also dedicated decades to the research of the Kozarnika Cave in Northwest Bulgaria.

The international scientific team who worked on the paper entitled “Initial Upper Palaeolithic Humans in Europe Had Recent Neanderthal Ancestry” includes the following authors: Mateja Hajdinjak, Fabrizio Mafessoni, Laurits Skov, Benjamin Vernot, Alexander Hübner, Qiaomei Fu, Elena Essel, Sarah Nagel, Birgit Nickel, Julia Richter, Oana Teodora Moldovan, Silviu Constantin, Elena Endarova, Nikolay Zahariev, Rosen Spasov, Frido Welker, Geoff M. Smith, Virginie Sinet-Mathiot, Lindsey Paskulin, Helen Fewlass, Sahra Talamo, Željko Rezek, Svoboda Sirakova, Nikolay Sirakov, Shannon P. McPherron, Tsenka Tsanova, Jean-Jacques Hublin, Benjamin M. Peter, Matthias Meyer, Pontus Skoglund, Janet Kelso, Svante Pääbo.

Lead co-author of the research, Mateja Hajdinjak, is seen in a laboratory environment in the Max Planck Institute of Evolutionary Anthropology in Leipzig, Germany. Photo: Alexander Huebner, Max Planck Institute of Evolutionary Anthropology, Leipzig, via the National Institute and Museum of Archaeology, Sofia

A photo showing part of the international research team who has worked on the latest research of the Bacho Kiro Cave. Back row (left to right): Naomi Martisius, Mateja Hajdinjak, Ivaylo Krumov, Svoboda Sirakova, Desislava Filcheva, Violet Fisch, Elena Endarova; front row (left to right): Vladimir Lafchiyski, Nikolay Sirakov, Nikolay Zahariev, Rosen Spasov, Tsenka Tsanova, Pedro Jorta, Svante Pääbo. Photo: Petar Petrunov via via the National Institute and Museum of Archaeology, Sofia

Back in 1938, an Anglo-American expedition found in the Bacho Kiro Cave a skeleton of a cave bear now kept at the British Museum in London.

The first full-fledged archaeological excavations in the Bacho Kiro Cave were carried out in the 1970s by a Bulgarian – Polish team.

In 2015, the excavations in the Paleolithic cave in Central Bulgaria were renewed precisely in the joint project of the National Institute and Museum of Archaeology in Sofia and the Department of Human Evolution at the Max Planck Institute for Evolutionary Anthropology in Leipzig, Germany.

Location of the Bacho Kiro Cave in Central Bulgaria. Map: Google Maps

Location of the Bacho Kiro Cave in Central Bulgaria. Map: Google Maps

A wide range of flint and bone artifacts and some animal bone remains from the latest excavations were showcased in the 2017 Bulgarian Archaeology Exhibition at the National Institute and Museum of Archaeology in Sofia back in February – April 2018.

Among the Paleolithic artifacts discovered in the Bacho Kiro Cave near Bulgaria’s Dryanovo showcased to the public back then were flint spear tips, a knife-shaped lamella, a scraper, flint lamellas, a penchant of cave bear teeth, a bone disc, and a rib from an ungulate mammal decorated through incisions.

Animal bone finds presented from the Pleistocene fauna presented in 2017 included a molar from the now extinct cave bear, a molar from a West Caucasian tur (Capra caucasica), a molar from Homo sapiens, a lower jaw from the now extinct steppe bison (Bison priscus), a lower jaw from a West Caucasian tur (Capra caucasica), molars from a wild horse (Equus ferus), and molars from a herbivore (likely the now extinct wild cattle aurochs (Bos primigenius).

Learn more about the Bacho Kiro Cave near Bulgaria’s Dryanovo in the Background Infonotes below!

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Background Infonotes:

The Bacho Kiro Cave is a Prehistory archaeological and cultural tourism site located near the town of Dryanovo and the Dryanovo Monastery in Central North Bulgaria.

It contains contains some of the oldest remains of Homo sapiens in Europe dating from the Paleolithic period (Old Stone Age).

It is also known for its marvelous karst formations and for being the first cave in Bulgaria to have been equipped for tourism purposes.

The Bacho Kiro Cave is located 300 meters away from the Dryanovo Monastery, one of the most famous and largest Bulgarian Orthodox Christian monasteries.

It was equipped for tourists as early as 1937 become the first cave in Bulgaria in that respect. It was named after Bacho Kiro (Kiro Petrov) (1835-1876), a Bulgarian revolutionary leader during the Bulgarians’ 1876 April Uprising against the Ottoman Empire who was captured and hanged by the Ottomans.

In 1962, the Bacho Kiro Cave was declared a natural landmark, and in 2002 its lighting and alleys were renovated. The cave is about 3,5 km (app. 2.1 miles) long, making it the 13th longest cave in Bulgaria. The permanent temperature inside is 13 degrees Celsius (55 degrees F).

The guided tours inside the Bacho Kiro Cave offer two routes, a short one (350 meters) and a long one (900 meters).

Many of the fabulous karst formations inside the cave have been named. These include the Jellyfish, the Bear Slide, the Throne, the Potato Slide, the Cave Eagle, the Dough, the Fountain, the Cave Ear, and the Lonely Stalactite. The cave’s most distant hall, dubbed “The Reception Room” features a giant stalactite which is 8 meters (25 fee) tall, and has a circumference of 1.5 meters (5 feet).

The Bacho Kiro Cave was formed about 1.8 million years ago by the waters of the Dryanovska River. The area used to be the bottom of a sea, and fossils of crabs can still be seen today inside the cave.

The first archaeological research inside the Bacho Kiro Cave was carried out in 1890 by Czech-Bulgarian high school teacher in Gabrovo, Stepan Jurinic (later a professor at Sofia University “St. Kliment Ohridski”). In 1895, it was visited by the fathers of Bulgarian archaeology, Czech-Bulgarian archaeologists Karel and Hermann Skorpil (the Skorpil Brothers).

In 1937, the Bacho Kiro Cave was researched by paleontologist Rafail Popov, and in 1938 by an Anglo-American expedition led by Prof. Dorothy Garrod, which had done research of Paleothic sites in Palestine before that.

One of their most interesting finds was a 3-meter-tall (10 feet) skeleton of a cave bear, which is kept today at the British Museum in London. The place where the cave bear was found is 300 meters inside the cave, and is known today as the Bear Lawn.

The first full-fledged archaeological excavations in the cave were carried out between 1971 and 1975 by a Polish – Bulgarian team led by Janusz Kozlowsky, Boleslaw Ginter, and Nikola Dzhambazov. The team discovered bone and flint tools, decorations, and human remains. One of the finds was a bone with an engraved geometric motif, said to be the earliest of its kind in Europe.

The archaeological excavations in the Bacho Kiro Cave have been resumed in 2015 for a total of three seasons with a joint project of the National Institute and Museum of Archaeology in Sofia and the Department of Human Evolution at the Max Planck Institute for Evolutionary Anthropology in Leipzig, Germany. Another nearby cave, Andaka, is also part of the renewed excavations.

The archaeological finds in the Bacho Kiro Cave near Bulgaria’s Dryanovo have led to the establishing of the so called Bacho Kiro Culture standing for a transitional phase between the Middle and Late Paleolithic (Stone Age) in Europe. It is characterized by the usage of new materials and techniques, and the emergence of the first adornments such as tooth pendants.

The Bacho Kiro Culture is deemed to be connected with local transitional cultures, rather than with the Middle East.

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