Frank Brown (1943–2017)

Abstract

Homo habilis, H. erectus, and H. heidelbergensis were presumably the first to leave Africa, with the European form of H. heidelbergensis later evolving into H. neanderthalensis in Europe and Denisovans in Northern Asia. The Denisovans are an extinct species or subspecies of human that ranged across Asia during the Lower and Middle Paleolithic. Denisovans are known from only a few fossil remains (small bone fragments, a few teeth, and one finger bone), so most of what is known about them comes from DNA evidence. Genetic evidence suggested that Denisovans split from the modern human lineage about 800 kya and from Neanderthals around 600 kya. Geneticists also concluded that Denisovans were more closely related to Neanderthals than modern humans based on genomic DNA sequencing. Further, genomic sequences indicated that modern humans, Neanderthals, and Denisovans shared a common ancestor, most likely H. heidelbergensis.The evidence collected so far suggests that Denisovans were the contemporaries of Neanderthals and Homo sapiens. Based on fossil and DNA evidence, the Denisovans lived in Siberia and East Asia, but it is difficult to know the exact time period when they existed because very few Denisovan fossils have been discovered. However, estimates indicate that Denisovans inhabited Asia around 50–200 kya. DNA sequencing of 11 present-day human populations showed that approximately 6% of contemporary Papuan DNA comes from Denisovans. Australian Aborigines and people from Southeast Asian islands also show Denisovan DNA, and about 0.2% of the DNA of mainland Asians and Native Americans is Denisovan. The DNA evidence points to a patchwork of people with and without Denisovan DNA, and estimates from DNA analysis conclude that interbreeding between anatomically modern humans and Denisovans occurred in Asia about 40 kya. By 10 kya, the Denisovan population was gone. The disappearance of the species resembles a mass extinction, but there's no apparent environmental catastrophe that appears to be involved with their disappearance. Researchers are not sure exactly when the Denisovans went extinct, and it is not known why they disappeared. Because there is very little fossil evidence for their existence and few artifacts, it may never be known why or how they went extinct.