For years we had a fairly clear narrative in our minds of what had happened to our ancestors. The specific story is that the Homo sapiens They left Africa, met some Neanderthals somewhere in the Middle East, had a couple of chance encounters of hybridization pulses and they continued on their way to conquer the world.
A change. However, a massive new study that just appear on the bioRxiv preprint server suggests that that picture is too simplistic. They were not specific meetings, but rather a continuous interaction throughout a huge “hybrid zone” which spanned from the Near East to Central Asia and Europe.
To get here, the study has analyzed an unprecedented amount of ancient DNA to draw the most detailed map to date of how we intermingled with our extinct cousins. and the result It is a gradient of miscegenation which extends for almost 4,000 kilometers.
Lots of volume. The study has not been limited to a few bones that have been found in isolation, but has used computer simulations and a data set of 1,264 paleogenomes. Something that corresponds to thousands of individuals older than 10,000 years.
Your conclusion. The Neanderthal DNA patterns that we carry today in our genetic material They are not well explained by “isolated pulse” models, but rather the symmetry found between the genomes of Europe and Asia indicates that there was prolonged contact.
In this way, as modern humans expanded out of Africa, which is what we know as Out of Africa, about 60,000 years agowere pushing a demographic frontier. On this advance front, gene flow was moderate but constant. That is why it was not a one-day event, but a long geographical process.
The how. To understand this you have to look complementary studies which suggest that the key is in spatial gradients. To visualize the concept, we can imagine a wave that advances as if they were the Sapiens who were moving and encountering the Neanderthals. But the key is that Neanderthal ancestry is not uniform.
This means that the first sapiens in Europe had a high level of Neanderthal DNA, but later expansions, such as the arrival of Neolithic farmers from Anatolia, they “watered down” that Neanderthal heritage, especially in Europe, creating a notable difference with the populations of Asia. This is where the study presented in 2026 confirms that only a model of persistent expansion with gene flow can explain why we find signs of interbreeding almost 4,000 km from the point of origin in the Near East.
When did it happen? This is where things get interesting when crossing the data with other recent studies, like the one published in Nature in 2024. And although the area was large, the time window was critical.
Analysis of more than 300 early human genomes points to a “single window” of major hybridization between 47,000 and 43,000 years ago. This excludes previous theories that suggested multiple, very ancient pulses. And to go a little further, there was a moment, when our species was securing its dominance in Eurasia, when the barrier between species blurred across a huge geographic swath.
A map of interactions. What this body of research suggests is that the hybrid zone encompasses almost all of the Neanderthal sites known as Western Eurasia, so it implies geographically extensive interactions.
However, as is often the case in science, caution must be maintained. This study has yet to undergo a full review and has limitations in that it is based on demographic assumptions and that it does not model the natural selection that we have in the genetic world. Even so, the image is increasingly clear: we are not the result of one species that replaced another suddenly. We are, in part, the result of a long border of contact where, for millennia, the line between “them” and “us” was much more blurred than we thought.
Images | Marc Tremblay
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