We have just discovered that 20% of our DNA comes from an unknown hominid population: population B

Perhaps at this point on remembering that human evolution is more like the branched structure of trees than to the linear image that we often use to illustrate it, that image in which our ancestors are irrigating and pertrechating tools. However, the bifurcations of these tree branches fail to illustrate some evolutionary changes.

Because sometimes species not only diverge, they also converge.

A recent genetic study has detected The trail in the human DNA of an old population that separated from our main lineage approximately 1.5 million years ago to converge some time later. The study has estimated that the genetic legacy of this second population (or population b) represents approximately 20% of our DNA today.

The study responsible for the study also raises the possibility that this legacy has been positive for our species. According to the hypothesis raised, these genes would have been contributed to improve our cognitive capacity.

“The question about where we come is one of those that has fascinated humans for centuries,” explained in a press release Trevor Cousins, co -author of the study. “For a long time, it had been assumed that we evolved from An ancestral continuous lineagebut the exact details of our origins are uncertain. “

The separation of these two evolutionary branches would have given rise to an evolution in parallel of the Populations A and B. The evolution of the population to correspond approximately what we already know, although the new work allows us to know in more detail its evolutionary history.

As explained by the team responsible for the study, after the separation of the two populations, the population A would have suffered a “Bottleneck”: While the population B prospered, the A had to cross a period in which its numbers were very scarce, a situation that also implied a drastic reduction in genetic diversity.

From the population A would have emerged the main human species of the past, including not only our species but also the “bifurcation” that would give rise to the arrival of Neanderthals and Denisovanosanother human species (or subspecies) that would have inhabited Central Asia hundreds of thousands of years ago.

Reunion between species

The history of population B is still enigmatic. The study has not recorded events such as population bottlenecks. We know that the core of this population disappeared but that at some point their roads crossed with the population A, giving rise to genetic exchange. He “Reunion” between populations It would have given more than one million years after separation, about 300,000 years ago, according to the estimates of the study responsible for the study. After this reunion, population B would fade without leaving another trace.

The genetic inheritance that each population would have left in modern humans would be unequal. While we should about 80% From our genetic material, to population B we could owe the remaining 20%. The study detected that these genes of population B would concentrate sections of the population’s own genes A.

This suggests, explains the team, that both populations would have been little compatible. The uncompatibilities would have been purified over the years through the process known as purification selection, a process in which natural selection is eliminating harmful mutations.

On this legacy, the team also indicates that these are genes closely linked to the functioning of the brain and the Information processing. This could imply that this small genetic inheritance could have had a great impact on the evolution of human intelligence and in the Evolution of our species.

The analysis focused on the study of contemporary humans and not on the bone remains of prehistoric populations. The team resorted to the 1000 Genomes Project initiative, thanks to which it had a large genetic database with information about inhabitants of Africa, Asia, Europe, and the Americas.

The details of the study were published In an article In the magazine Nature Genetics.

The history of evolutionary convergence is long. Perhaps the best known case is that of the Neanderthals (Homo Neanderthalensis). This already extinct species occupied Europe and Asia tens of thousands of years before our species left Africa but, once they found themselves They coexisted in various areas of Eurasia.

Thanks to its genetic legacy (which varies according to populations but usually around 1% or 2% among non -Afro -descendant), we know that the coexistence of sapiens and Neanderthals gave a lot of: The union of these species engendered hybrids whose lineages ended up merging with those who gave rise to contemporary humanity.

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