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.
Contents
- Genome sequencing
- Y DNA and mtDNA
- Out of Africa
- Relationship with Neanderthals
- Relationship with modern human populations
- References
The remains consist of a single bone—left femur—of a male hunter-gatherer, which was discovered in 2008 protruding 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.
Y-DNA and mtDNA
Since 2016, Ust'-Ishim man has been classified as belonging to Y-DNA haplogroup K2a*, which is defined by the SNP M2308. (Before 2016, the remains were believed to belong to Haplogroup K2.)
The remains belonged to mitochondrial DNA haplogroup (mtDNA) R*.
Both of these haplogroups and descendant subclades are now found among populations throughout Eurasia, Oceania and The Americas, although no direct descendants of Ust Ishim man's specific lineages are known from modern populations. Y-DNA K2 is believed to have originated with a man who lived in South East Asia, 47,000–55,000 years BP.
Out of Africa
Examination of the sequenced genome indicates 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 has genetic links to 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 La Braña man – a hunter-gatherer who lived in La Braña, Spain about 8,000 years ago.
It is thought that Ust'-Ishim man is, on the whole, not more closely related to either of the first major migrations of Homo Sapiens eastward into Asia: a group that migrated along the southern coast, or a second that moved north-east through Central Asia.
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 and 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.
Relationship with modern human populations
Ust’-Ishim man has no living descendants. He is more closely related to modern East Asian and Oceanian populations than to modern West Eurasian populations, such as the current residents of the Ust’-Ishim area. Modern West Eurasians are more closely related to other ancient remains.
In a 2016 study, modern Tibetans were identified as the modern population that has the most alleles in common with Ust'-Ishim man. According to a 2017 study, "Siberian and East Asian populations shared 38% of their ancestry" to Ust’-Ishim man.