The Neanderthals Among Us

A long debated question has been answered. Humans and Neanderthals did interbreed and their genes live on within most of us.

In a paper—‘A Draft Sequence of the Neanderthal Genome’—published in Science, a team of researchers has found that Neanderthals did interbreed with modern humans. The results show that modern humans in places other than Africa share between 1 to 4 per cent of their genes with Neanderthals. According to Dr David Reich of Harvard Medical School in Boston, who worked on the study, “The proportion of Neanderthal-inherited genetic material is about 1 to 4 per cent. It is a small but very real proportion of ancestry in non-Africans today.” The researchers have stated that “the closest evolutionary relatives of present-day humans, who lived in large parts of Europe and western Asia before disappearing 30,000 years ago … shared more genetic variants with present-day humans in Eurasia than with present-day humans in sub-Saharan Africa, suggesting that gene flow from Neanderthals into the ancestors of non-Africans occurred before the divergence of Eurasian groups from each other’’.

Clearly then, the facts suggest one of two possibilities: that the admixture of Neanderthal genes in the genome of modern humans took place after they left Africa but had yet not separated into different groups that went on to inhabit the rest of the world, or those that left Africa were unique in that they of all Africans had intermixed with Neanderthals. The second possibility is far more remote, but cannot be categorically ruled out.

The comparison between the human and Neanderthal genome was made possible after the researchers “prepared a draft sequence of the Neanderthal genome composed of more than 4 billion nucleotides from three individuals. Comparisons of the Neanderthal genome to the genomes of five present-day humans from different parts of the world identify a number of genomic regions that may have been affected by positive selection in ancestral modern humans, including genes involved in metabolism and in cognitive and skeletal development’’. The DNA used in the research was taken from 40,000-year-old Neanderthal bones, and special techniques had to be used to rule out any contamination by human DNA.

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