Unknown species may have interbred with human ancestor

Hyperaxion Feb 29, 2020

A study at the University of Utah revealed that the Neanderthals and Denisovans were the result of interbreeding between their common ancestor and an unknown species.

The researchers came to this conclusion after analyzing and comparing the genomes and mutations of different hominids and identifying evidence that our evolutionary line had more contributions than previously thought.

Superarchaics, the unknown human species

In fact, the study began as part of an effort to, through the analysis of genetic patterns of ancient populations, identify mutations inherited from our ancestors and try to discover more about now-extinct groups.

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However, evidence suggests that additionally to modern humans being related to species that were already known – genetic mapping revealed that 1.5% to 6% of the DNA of non-African populations comes from Neanderthals and Denisovans -, more interbreeding may have occurred over the thousands of years.

Huge implications

According to the scientists, a mysterious species of hominid that the researchers called “superarchaics” interbred with a common ancestor of the Neanderthals and Denisovans about 700 thousand years ago in Eurasia – an event that has genetic and evolutionary implications and suggests that the timeline of human migration from Africa needs to be revised.

Evolutionary patchwork

The genetic survey – in which the researchers examined mutations shared between Africans, modern Europeans, Neanderthals and Denisovans – pointed out that thousands of years ago, there were at least 5 episodes of interbreeding between species.

Neanderthal
Neanderthal. (Credit: NPR).

One of these events took place 700,000 years ago, between the common ancestor of the Neanderthals and Denisovans with the superarchaics population, a species that separated from the other human populations about 2 million years ago.

1 million years away from each other

As far as we know, these two human populations – the superarchaic and the ancestor of the Neanderthals and Denisovans – are the most distant (evolutionarily speaking) to reproduce with each other, being separated by more than 1 million years.

 Denisovan girl.
Denisovan girl. (Credit: Medium).

For comparison, modern humans and Neanderthals were separated by about 750,000 years when they met in Europe.

At least 3 human migrations have occurred

Finally, concerning human migration, the researchers found evidence that suggests that at least 3 of them have taken place.

The first would have occurred about 2 million years ago, when superarchaic hominids migrated to Eurasia and established a relatively large population there, made up of between 20 thousand to 50 thousand individuals.

The second occurred with the arrival of a group composed of the common ancestor of the Neanderthals and Denisovans on the continent, more or less 700 thousand years ago, when miscegenation started to happen between the descendants of the superarchaics and the newly arrived hominids.

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This, in turn, eventually gave rise to a new species that not only replaced the superarchaic, but was divided into 2 subpopulations – one in the west and the other in the east: the Neanderthals and Denisovans.

Then, it was the turn of modern humans to leave the African continent, around 50 thousand years ago, to settle in Eurasia and mix with the populations that already lived in the area, that is, with the Neanderthals and, later, with the Denisovans.

And who are the hominids of this mysterious superarchaic family?

Miscegenation

Well, scientists know that 2 million years ago, when that group separated from the human lineage, at least 2 species of hominids inhabited Eurasia.

One was Homo erectus – our first ancestors to walk upright – and the other was Homo antecessor, whose fossils were discovered in Spain.

However, there may have been other species that have not yet been discovered.

(Credit: New Atlas).

What is clear is that our ancestors did not seem to care so much about miscegenation or to relate to the “slightly different” – and that our evolutionary line, as well as our DNA, consists of a real patchwork created from the contribution of countless species.

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