Human remains, unearthed near Casablanca, could belong to the ancestor we had in common between Homo Sapiens, Neanderthals, and Denisovans. This discovery shifts the potential origin of our story, demonstrating that these potential candidates already occupied northwestern Africa precisely during this period.
The study, published in the journal
Nature, focused on fossils recovered from the Grotte à Hominidés site, located in the Thomas I quarry. These remains (vertebrae, teeth, and jaw fragments) gave up their secrets thanks to a remarkably precise dating method. Initial analyses reveal that this population lived 773,000 years ago, that is, just before the period of separation that gave rise, on one side, to the lineage of modern humans, and on the other, to that of our Denisovan and Neanderthal cousins.
Mandible, teeth, and vertebrae extracted.
Scale: 2 in (5 cm). An exceptionally precise chronological window
Dating was possible because the sediments that contained these fossils had retained a record of the last major reversal of Earth's magnetic field (a reversal of the magnetic poles known as the Matuyama-Brunhes reversal). It was thus possible to certify that the hominins were present during this geophysical event. This proved to be a valuable aid as precise chronological markers are difficult to establish for this period of the Pleistocene.
Until now, our common ancestor was considered to be
Homo antecessor. Its fossils, discovered in Spain, had been dated to approximately 800,000 to 950,000 years ago. But this recent discovery in Morocco reveals that nearly 800,000 years ago, at least two morphologically distinct human populations were evolving in parallel, one in southwestern Europe, the other in northwestern Africa, while the last common ancestor of all more recent human lineages had only just existed.
Analysis of the fossils, notably by micro-computed tomography, revealed both modern and primitive traits. Indeed, dental morphology shows similarities with that observed later in Homo sapiens and Neanderthals. In contrast, the overall shape of the mandible remains more archaic, reminiscent of that of Homo erectus.
A new actor in the scenario of African origins
Until now, no African fossil had been dated to this pivotal period. The scientific community therefore agreed to consider that our origin was Eurasian following the discovery of Homo antecessor fossils. However, it is now known that a population with characteristics plausible for being at the base of our lineage was indeed present in Africa at that time.
Nevertheless, it is advisable to remain cautious about the interpretation of these results. They do not assert that these hominins are the direct ancestors of modern humans. Rather, they describe a population that could be very close to the root of our family tree.
This configuration reinforces the idea of an early diversification of the genus Homo across the Old World, with multiple and interconnected evolutionary centers. The Maghreb, with its rich and continuous archaeological sequences, is increasingly appearing as a key region for understanding the dynamics that ultimately led to the emergence of our species on the African continent, much later, around 300,000 years ago.
Article author: Cédric DEPOND