The Denisovans--An ancient type of human
by Darvin Martin on Thursday, August 30, 2012 at 10:25pm ·
The genome of another ancient type of human has been decoded. The Denisovans lived in Eastern Asia up to about 30,000 years ago, parallel to the Neanderthals in Europe. When comparing the Denisovan genome to genomes of living humans around the world, humans in Southeast Asia share about a 6% greater similarity among these differences than the rest of the population. When comparing the Neanderthal genome to genomes of living humans around the world, we find that Europeans share between 1-4% greater similarity (among the differences between Neanderthals and modern humans) than the rest of the world population.
All humans around the world living today descend from common ancestors living in East Africa between 140,000 and 200,000 years ago. The Denisovans and Neanderthal represent far more ancient human lines that moved out of Africa to settle in Europe and Asia between 350,000 and 600,000 years ago. About 60,000 years ago, modern humans of the yDNA haplogroups C and D moved out of Africa at the southern end of the Red Sea between Djibouti and Yemen. The followed the coastline of the Indian Ocean. Both found their way to India. From there the C groups settled in Southeast Asia, arriving in Australia at least 40,000 years ago. The D groups transverse China and settled north as far as Korea and Japan.
In Southeast Asia, some modern humans within the C groups interbred with the ancient human Denisovans living there. This occurred often enough for markers of Denisovan DNA to be found in the modern human population. Madame X, our Denisovan DNA source, lived in the Altai Mountains of Siberia 41,000 years ago. Modern humans probably drove the Denisovan populations to extinction, and perhaps the populations in South East Asia were already facing extinction when Madame X lived in Siberia. It is unknown if or how Denisovans relate to the Homo floresiensis population in Indonesia, since DNA has not been successfully extracted from Homo floresiensis remains.
Our first modern human ancestors to enter Europe also interbred with Neanderthals, as evidenced by Neanderthal markers found in the modern European population today. These were probably the Cro-Magnon with yDNA haplogroup I and a minority of K and G also represented.
Denisovan DNA adds to the complexity of early human origins. While the direct paternal (yDNA) and direct maternal (mitochondrial) DNA of all living humans have the same “recent” source in East Africa, our autosomal DNA, representing the mixing between both parents, shows a far earlier genetic history, connecting to earlier groups of humans that have long since gone extinct.