Ust'-Ishim man

Ust'-Ishim man is the term given to the 45,000-year-old remains of one of the early modern humans to inhabit western Siberia. The fossil is notable in that it had intact DNA which permitted the complete sequencing of its genome, the oldest modern human genome to be so decoded.

Discovery

The remains consist of a single bone—left femur—of a male hunter-gatherer, which was discovered in 2008 protuding from the bank of the Irtysh River by Nikolai Peristov, a Russian sculptor who specialises in carving mammoth ivory. Peristov showed the fossil to a forensic investigator who suggested that it might be of human origin. The fossil was named after the Ust'-Ishim District of Siberia where it had been discovered.

Genome sequencing

The fossil was examined by paleoanthropologists in the Max Planck Institute for Evolutionary Anthropology, located in Leipzig, Germany. Carbon dating showed that the fossil dates back to 45,000 years ago, making it the oldest human fossil to be so dated. Scientists found the DNA intact and were able to sequence the complete genome of Ust'-Ishim man to contemporary standards of quality. Though genomes have been sequenced of hominins pre-dating Ust'-Ishim man, this is the oldest modern human genome to be sequenced to date.

Out of Africa

Examination of the sequenced genome indicates that Ust'-Ishim man belonged to the same group of early humans as the Mal'ta boy, a four-year-old who lived 24,000 years ago along the Bolshaya Belaya River near today's Irkutsk in Siberia (see Mal'ta-Buret' culture), and the La Braña skeleton of a hunter-gatherer who lived in La Braña, Spain about 8000 years ago. This relationship implies that Ust'-Ishim man belonged to the first wave of humans to migrate out of Africa into Eurasia, before or at the time when that population forked out to the east into Siberia and to the west into Europe.

Ust’-Ishim man is more closely related to the East Asians of today than to today's Europeans. Modern Europeans, on the other hand are thought to have derived their ancestry from three bloodlines, namely that of a hunter-gatherer who lived 45,000 years ago and most probably originated in the second human migration out of Africa into Europe, mixed with genes from an early agriculturist who moved into Europe about 9,000 years ago, and finally, DNA from a steppe nomad of northwestern Asia from a population that has died out completely but has contributed DNA to a wide range of modern humans including Europeans and native Americans.

It is thought that Ust'-Ishim man is not more closely related to any of the two major migration events into Asia (the first one through the southern coast originated populations such as Onge of Andaman islands, and the second one to the North that originated Asians), so Ust'-Ishim man represents another migration attempt into the continent that not shows any kind of descendant between current human populations.

Relationship with Neanderthals

Analysis of modern human genomes reveals that humans interbred with Neanderthals between 37,000 and 86,000 years ago, resulting in the DNA of humans outside Africa containing between 1.5 to 2.1 percent DNA of Neanderthal origin. Neanderthal DNA in modern humans occurs in broken fragments; however, the Neanderthal DNA in Ust'-Ishim man occurs in clusters, indicating that Ust'-Ishim man lived in the immediate aftermath of the genetic interchange. The genomic sequencing of Ust'-Ishim man has led to refinement of the estimated date of mating between the two hominin species to between 52,000 and 58,000 years ago.

No relationship between Denisovans and the Ust'-Ishim man has been checked, although Denisovans have some descendants in Oceania and Asia.