Much speculation and debate has taken place, but the most recent evidence suggests that our species, Homo sapiens, appeared between 200,000 and 300,000 years ago. It appeared in what is now Africa, although the precise dating is constantly changing as archaeological discoveries are made. What is clearer, however, is that what happened before is still not known.
We don’t know how we were possible, and our understanding of how the world evolved at that time, before the emergence of modern humans, relies on a limited body of fossil and archaeological evidence, meaning that reconstruction of this story still has gaps, unfinished work.
Only in recent decades have researchers been able to fill in some of these gaps by identifying several species that preceded ours, such as Homo erectus and Homo heidelbergensis. These two species, and perhaps others, have played essential roles in the history of human evolution. At one point they acquired anatomical characteristics and, at another time, behavioral characteristics, until they reached forms more recognizable for what we are today. But progress itself is made up of obstacles, of breaks that come between us, nature turning in on itself when, for example, what we call extinction occurs. Have men ever been on the verge of extinction since then until today?
In a “bottleneck”?
It turns out thata recent study suggests yes. This may have happened when the human species experienced a severe decline in its breeding population, or what researchers call a “bottleneck.” This was almost a million years ago, but the human species remained like this, on the verge of losing the possibility of having descendants, for more than 100,000 years.
However, this same episode may also have led to the development of the most common ancestor of modern humans, Neanderthals. This is the conclusion of a study for which the authors examined the genomes of more than 3,150 modern humans from ten African populations and forty non-African populations.
Thanks to a new analytical tool developed for the occasion, researchers were able to deduce with great precision the size of the group which constitutes the ancestors of modern humans by examining the diversity of genetic sequences observed in their descendants.
Previous work had already suggested that human chromosome 2 developed between 900,000 and 740,000 years ago, following the fusion of two other chromosomes. The latest research highlights that this demographic situation may have divided humans into small, distinct groups that, over time, may have developed anatomical differences large enough to give rise to distinct surviving populations. This is how Neanderthals, Denisovans (a now-extinct relative of modern humans who lived in Siberia and East Asia) and us appeared.
Neanderthals and Denisovans share this chromosomal fusion with us, which is strong evidence, when linking their presence in a timeline, that we actually avoided extinction by strengthening ourselves. In other words, it’s possible that this merger occurred on the brink of extinction.
There has been much speculation and debate about this, but the most recent evidence suggests that our species, Homo sapiens, appeared between 200,000 and 300,000 years ago. It appeared in what is now Africa, although the precise dating is constantly changing as archaeological discoveries are made. What is clearer, however, is that what happened before is still not known.
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