Scientists find oldest human fossil ever recorded, rebuild lost genome

An international team of scientists collected and sequenced genomic DNA from a human thigh bone found in Siberia and estimated to be around 45,000 years old.

by John Tyburski

Copyright © Daily Digest News, KPR Media, LLC. All rights reserved.

First published at Daily Digest News on October 22, 2014

The oldest genetic record for modern humans has been reconstructed by scientists working with a human thighbone fossil found on a Siberian riverbank. The research report was published on Wednesday in the journal Nature and provides new insights on the movement of modern humans northward out of Africa some 60,000 years ago. The thighbone genome also supports the provocative notion that early modern humans interbred with Neanderthals before the Neanderthals died off.

“It’s irreplaceable evidence of what once existed that we can’t reconstruct from what people are now,” said John Hawks, a paleoanthropologist at the University of Wisconsin, in a statement. “It speaks to us with information about a time that’s lost to us.” Hawks was not involved in the study.

The present study was led by Svante Paabo, a geneticist at the Max Planck Institute for Evolutionary Anthropology in Leipzig, Germany. Paabo and colleagues have spent over three decades perfecting their extraction of DNA from fossilized remains. In December, they published a complete genomic sequence for Neanderthals based on DNA acquired from a single toe bone. The scientists found that Neanderthals and modern humans share a common ancestor that lived an estimated 600,000 years ago.

The DNA that Paabo and colleagues sequenced was extracted from a fossilized human thighbone found by collector Nikolai V. Peristov during his travels along the Irtysh River in Siberia, Russia. Peristov found the bone in shallow water along the riverbank near the settlement of Ust’-Ishim and turned it over to the Russian Academy of Sciences.

The Russian scientists discerned that the bone was more like modern human than Neanderthal and had the fossil radiocarbon dated to an estimated 45,000 years old. The thighbone of “Ust’-Ishim man” is the oldest modern human fossil ever found outside of the Near East and Africa. Paabo and colleagues took samples of the bone back in 2012 and were able to extract surprisingly well-preserved DNA fragments.

“This is an amazing and shocking and unique sample,” said David Reich, a geneticist at Harvard Medical School and co-author of the new study.

The genome, identified as that of a male because of the presence of a Y chromosome, was compared to that of ancient man and modern living humans. The DNA is more like non-Africans and not any more related to ancient Europeans than to East Asians. Based on this evidence, the group concluded that Ust’-Ishim man belonged to a human group that gave rise to all non-African humans.

The genomic sequence of Ust’-Ishim man also reveals less fragmentation in Neanderthal-like fragments contained within, indicating a closer heritage with Neanderthal than Africans exhibit. Previous estimates placed interbreeding between modern humans and Neanderthals to within 37,000 to 86,000 years ago. Paabo and his team provide evidence that narrow this range down to from about 50,000 to 60,000 years ago.