A golden age of ancient DNA science begins

A few years back we fossil-jocks couldn't agree about whether interbreeding had actually occurred or not. The case now seems to be closed thanks to the geneticists.

Interbreeding occurred, but it wasn't terribly common. Around 2 per cent of the genome of non-African people was inherited from Neanderthals, with slightly more DNA in Indigenous Oceanic Southeast Asians, New Guineans and Australians coming from the mysterious Denisovans (on top of their Neanderthal inheritance).

Even among some living African populations, there is evidence for DNA inherited from an archaic species living on that continent perhaps as late as 30 thousand years ago.

I suspect there will be more evidence found in the future, from other, perhaps as yet unknown, archaic species.

One of the new studies - led by Benjamin Vernot from the University of Washington - examined 35 new genomes sequenced from people living in 11 locations in the Bismarck Archipelago of New Guinea to get a better handle on gene sharing with our archaic cousins.

They confirmed evidence for ancient gene flow with the Neanderthals and have better characterised mating with the mysterious Denisovans, by comparing their new genomes with around 1,500 other human samples.

The New Guinean samples showed between 1.9 and 3.4 per cent of their genomes to be derived from the Deniosvans.

They also showed that a second 'pulse' of interbreeding is seen among living East Asians, Europeans and South Asians that wasn't shared with New Guineans.

There were seemingly three separate interbreeding events with the Neanderthals: one with the ancestors of New Guineans and Australians, one with early East Asians and one with the ancestors of South Asians and Europeans.

Geneticists have now turned their attention to the specific genes that have been inherited by living humans from our archaic cousins and their consequences for understanding human adaptations and disease.

I've looked at some of these previously, like those associated with the human immune system and high altitude adaptation.

The really exciting area to be explored in the future is whether genes associated with features of the skeleton can be identified, helping us to make a direct connection with the physical changes documented in the fossil record and to understand how and why such changes came about.