Homo neanderthalensis adult male, reconstruction.
Homo neanderthalensis adult male. Reconstruction by John Gurche for the Human Origins Program.

This year’s Nobel Prize for Physiology or Medicine was awarded to Svante Pääbo, a Swedish evolutionary biologist who sequenced the first Neanderthal genome in 2010. He spearheaded a new field known as paleogenomics, renewing debates about interbreeding between our earliest ancestors and their Neanderthal neighbours. We now know, for instance, that European and Asian populations have inherited around 2 per cent of their genome from Neanderthals: evidence of an intimacy between our species that had long been questioned.

We diverged from Neanderthals around 650,000 years ago. They had similar sized brains to us and were an intelligent and social species. Despite this, the superior cognitive capacities of early modern humans – evidenced through superior technology, art, and cultural practices – may have allowed them to eventually outcompete our doomed cousins.

In the same month as receiving the Nobel, Pääbo’s team published research in the journal Science, providing compelling evidence of the genetic changes underlying this cognitive divergence. They considered the TLKT1 gene, in which only one amino acid out of hundreds differs between Neanderthal and modern human DNA. The human version of TLKT1 is preferentially expressed in the neocortex during fetal development, a region of the brain involved in complex tasks like conscious thought and language.

Based on these observations, the team hypothesised that the human-specific changes may have been a key driver of advanced cognition during human evolution. They were able to demonstrate that the human version of TLKT1 drives significantly greater proliferation of young brain cells in the neocortex, known as neural progenitors, when compared to the Neanderthal version.

The work provides compelling evidence that a single genetic change may have driven growth of the neocortex, or a greater density of neurons within it, among early humans, potentially contributing to our cognitive advantage over Neanderthals and other extinct hominins.

This piece is a preview from our New Humanist winter edition. Subscribe here.