Why do some people have more Neanderthal DNA than others? Scientists now have an explanation

A new analysis has revealed the reason for the presence of Neanderthal DNA in human populations in Europe and Asia.

The study, published inScience Advancesjournal, has deepened scientists' understanding of the ancient genomes that may have medical relevance today. It tracks the hereditary legacy of the age-old relatives of our species with more accuracy, using the critical mass of significant data.

Many humans alive today have a tiny per cent of Neanderthal DNA because of the prehistoric sexual encounters between our ancestors and the Stone Age hominins, who became extinct around 40,000 years ago. However, East Asian populations have a slightly higher concentration of Neanderthal DNA in their genomes.

This difference has always baffled scientists as they have found Neanderthal remains extensively across Europe and the Middle East but not further east of the Altai Mountains in Central Asia.

"So what's puzzling is that in an area where we've never found any Neanderthal remains, there's more Neanderthal DNA," said study co-author Mathias Currat, a senior lecturer of genetics and evolution at the University of Geneva.

Neanderthal DNA makes up about 2 per cent of the genetic makeup of Eurasians. However, it makes up about 4 per cent of the genetic makeup of East Asians, Currat said.

Currat and his colleagues at the University of Geneva analysed the distribution of the DNA inherited from Neanderthals in the genomes of humans over the past 40,000 years. After the research, they came up with a possible explanation for this discrepancy.

"We are beginning to have enough data to describe more and more precisely the percentage of DNA of Neanderthal origin in the genome of Sapiens at certain periods of prehistory," Currat explained.

According to the study, the distribution of Neanderthal DNA did not always look as it does now.

The research found that in samples older than 20,000 years, genomes of Stone Age Homo sapiens in Europe contained a slightly higher proportion of Neanderthal DNA than those from Asia.

Thus, the present pattern of a higher percentage of Neanderthal ancestry in Asian populations compared to those in Europe developed at a later stage, the research team concluded. It possibly happened during the Neolithic transition when farming replaced hunting and gathering as a way of life.

However, Currat said it was unclear how this transition unfolded in Asia due to the relative lack of data. The study included 1,517 samples from Europe versus 1,108 from Asia.

(With inputs from agencies)

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