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Neanderthal genes are being purged from our DNA

14 November 2016

By Matthew Thomas

Appeared in BioNews 877

The process of natural selection has removed the majority of Neanderthal DNA from the modern human genome, leaving behind a handful of beneficial genes, two recent studies have suggested.

The genomes of many people of non-African descent alive today contain a small percentage of Neanderthal DNA, as a result of interbreeding between modern humans and Neanderthals before the species went extinct around 40,000 years ago. It is estimated that between one and four percent of the modern, non-African genome is Neanderthal.

In one study, researchers used computer simulations to show that the larger effective population size of ancient Homo sapiens compared to Neanderthals – that is, more people who were reproducing – allowed natural selection to push out large swathes of Neanderthal DNA from the human genome. This led to the removal of genes that were harmless to Neanderthals, but may have had small but damaging effects on their human carriers.

'Weakly deleterious variants that could persist in Neanderthals could not persist in [early modern] humans,' said Ivan Juric, a geneticist at 23andMe and first author of the study, published in PLOS Genetics. 'We think that this simple explanation can account for the pattern of Neanderthal ancestry that we see today along the genome of modern humans.'

Findings from a separate study, published in Current Biology, suggested that the remaining Neanderthal DNA in modern humans might have given our ancestors important advantages. The researchers in this second study found ancient sequences of DNA that were present at frequencies higher than expected if they were not proving beneficial. These groups of genes, known as haplotypes, were related to the immune system and skin pigmentation.

Through scouring the genomes of people from Europe, East and South Asia, and Island Melanesia, the team found 126 haplotypes that originated in Neanderthals as well as Denisovans, another ancient hominin cousin.

'Our work shows that hybridisation was not just some curious side note to human history, but had important consequences and contributed to our ancestors' ability to adapt to different environments as they dispersed throughout the world,' said Dr Joshua Akey, a geneticist from the University of Washington School of Medicine, Seattle, and senior author of the second study.

It seems that, while natural selection whittled away the majority of Neanderthal genes, our ancestors kept a handful of advantageous alleles that may have provided, as Dr Akey said, 'an efficient way for modern humans to quickly adapt to the new environments they were encountering'.

The Scientist | 10 November 2016
Current Biology | 10 November 2016
New Scientist | 08 November 2016
Science Daily (press release) | 10 November 2016
PLOS Genetics | 08 November 2016
Smithsonian | 10 November 2016


22 January 2018 - by Ewa Zotow 
The programme starts with a bold statement: 'No other field of science has experienced such an upheaval in the last few years as human evolution.' There is a reason for it: the recent addition of the DNA research to the toolbox of techniques available to evolutionary scientists has led to remarkable findings...
04 December 2017 - by Martha Henriques 
A total of 49 genes have been found to influence earlobe shape and attachment, new research has found...
27 February 2017 - by Annabel Slater and Ari Haque 
Neanderthal DNA is still involved in controlling a range of traits in modern humans...

09 May 2016 - by Dr Özge Özkaya 
A study of ancient DNA obtained from prehistoric human remains has revealed details about modern humans before farming began, going back to their arrival in Europe around 45,000 years ago...
22 February 2016 - by Isobel Steer 
Neanderthal-derived DNA influences our risk of certain diseases, including addiction, blood clots, skin conditions and depression, a recent study has found....
17 August 2015 - by Isobel Steer 
Compared to ancestral humans, most modern people have lost 40.7 million base pairs of DNA...
03 February 2014 - by Dr Anna Cauldwell 
Genes linked with type 2 diabetes, Crohn's disease and even smoking addiction were acquired through interbreeding with Neanderthals, a study published in Nature suggests...
06 January 2014 - by Dr Charlotte Warren-Gash 
A gene variant increases the risk of type 2 diabetes in Latin American populations, according to a study in Nature...

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