Australia: The Land Where Time Began

A biography of the Australian continent 

Genome sequence of a 45,000-year-old modern human from western Siberia

In this article the authors¹ present the genome sequence, of high quality, of a modern human male from Siberia that has been dated to about 45,000 BP. They found that this individual derived from a population living before or possibly simultaneously with, the populations of western and eastern Eurasia separated from each other, and he carries a similar amount of Neanderthal ancestry as Eurasians of the present. The study found, however, that the genomic segments of Neanderthal ancestry were substantially longer than those that have been observed in individuals of the present, which indicates that in the ancestral people of this individual the gene flow occurred 13,000-7,000 years prior to the time he lived. The authors estimated an autosomal mutation rate of 0.4 x 10^-9 to 0.6 x 10^-9 per site per year, a Y chromosomal mutation rate of 0.7 x 10^-9 to 0.9 x 10^-9 per site per year, that was based on the substantial substitutions that have occurred in non-Africans compared to this genome, and a mitochondrial mutation rate of 1.8 x 10^-8 to 3.2 x 10^-8 per site per year, based on the bone age.

A human left femoral diaphysis that was relatively complete was discovered on the bank of the Irtysh River, near the settlement of Ust’-Ishim in western Siberia, Ormsk Oblast, Russian Federation, in 2008. Though the exact locality is not certain, the femur was eroding out of alluvial deposits on the left bank of the river to the north of Ust’-Ishim. At this site fossils are found in layers of sand and gravel that are believed to be about 50,000-30,000 years old (from the Marine Oxygen Isotope Stage 3) in which Late Pleistocene fossils and possibly redeposited Middle Pleistocene have been found.

Morphology

A large gluteal buttress and gluteal tuberosity is present on the proximal end of the bone, and the midshaft is dominated by a marked linear aspera, the result of which is a cross section that is tear-drop shaped. At the proximal end of the shaft the morphology is similar to that of modern humans from the Upper Palaeolithic, and distinct from that of Neanderthals, but the mid-section of the shaft that is teardrop-shaped in cross section is similar to that seen in most humans and most anatomically modern humans from the Upper Palaeolithic. When this is taken together it indicates that the Ust’-Ishim femur is derived from a modern human.

Sources & Further reading

1. Fu, Qiaomei, 2014, Genome sequence of a 45,000-year-old modern from western Siberia, Nature, Vol. 514, No. 13810, 445-449 doi:10.1038/nature13810