Scientists reconstruct genome of 45,000-year-old human skull from Czech Republic

An international team of researchers has reconstructed the oldest modern human genome from a human skull found in the modern Czech Republic that is thought to be at least 45,000 years old.

The complete female skull, housed in the National Museum in Prague, was named Zlatý Kůň, Golden Horse in Czech, after the hill where it was found in a cave in the 1950s. Based on stone and bone tools found near the skull, it was initially assumed to be about 30,000 years old. But recent genomic analysis suggests that the skull is much older.

Solving the puzzle of the skull's age resulted from the collaboration of Czech scientists Jaroslav Brůžek and Petr Velemínský with the genetics laboratories of the Max Planck Institute for the Science of Human History in Germany.

The research appears in the journal Nature Ecology & Evolution April 7. 

Initial radiocarbon dating of the skull previously suggested that it was only 15,000 years old. The research team was surprised to find in the initial genetic analysis that the mitochondrial DNA of the Zlatý Kůň skull looked very ancient. 

They had a cranial bone fragment of the skull analyzed by radiocarbon dating, which produced three different dates, indicating that there might be contamination, making the skull difficult to date. After further genetic analysis of the fragment, it seemed likely that the contamination was from the bovine animal glue used in the skull's preservation about 70 years ago.

The research team then studied the nuclear genome of the skull, sequencing about 20 million DNA fragments. From these data they were able to compare the genetic relationship of Zlatý Kůň to other ancient humans and to present-day humans.

One clue to the actual age of the skull came from the length of its segments of DNA that are associated with Neanderthal ancestry. The longer these DNA segments, the older the specimen, because it is closer to the time of the initial admixture of Neanderthals and human beings, the researchers write.

The Zlatý Kůň DNA segments associated with Neanderthals were very long, indicating that the skull dates about 2,000 years after the initial Neanderthal admixture. This would make the Zlatý Kůň individual "one of the earliest Eurasian inhabitants following the expansion out of Africa," the researchers state.

There are very few genomic specimens of early Europeans, and Zlatý Kůň, so far, is the oldest human who has been sequenced. Interestingly, the research data also show that there is no continuity between Zlatý Kůň and modern humans.

The researchers speculate that this might be because the Campanian Ignimbrite volcanic eruption in Italy about 39,000 years ago is thought to have "severely affected the climate in the Northern Hemisphere. This could have reduced the viability of Neanderthals and early modern humans in large parts of western Eurasia."

The researchers conclude: "Future genetic studies of these and other early European individuals will help to reconstruct the history of these first modern humans who expanded into Eurasia after the out-of-Africa event and before the major dispersal that gave rise to modern-day non-African populations."

A short video of the project can be seen here.