Fossilized bones and teeth, about 773.000 years old, discovered in a cave in Morocco, provide a deeper understanding of the origin of the species Homo sapiens in Africa, representing the remains of archaic humans who may have been close ancestors of our species.
Researchers said the fossils - the lower jaws of two adults and a child, as well as teeth, a thigh bone and several vertebrae - were found in a cave called Grot a Ominid, at a site in the city of Casablanca. The cave, according to the findings, likely served as a den for raptors, and the thigh bone bears bite marks, suggesting the individual may have been hunted or that its remains were later torn apart by hyenas, Reuters reports.
According to the researchers, the most appropriate interpretation is that these fossils represent an evolved form of the archaic human species Homo erectus, which first appeared about 1,9 million years ago in Africa and later spread to Eurasia.
The bones and teeth show a mix of primitive and more modern human characteristics. They fill a gap in the African fossil record of species from the human evolutionary lineage - the so-called hominins - from a period between about a million and 600.000 years ago.
According to the researchers, the fossils may represent an African population that existed just before the evolutionary separation of the lineages that led to Homo sapiens in Africa and two closely related hominin species - Neanderthals and Denisovans - that inhabited Eurasia.
"I would be cautious about labeling them as 'the last common ancestor,' but they are probably very close to the populations that later gave rise to the African lineage of Homo sapiens and the Eurasian lineages of Neanderthals and Denisovans," said paleoanthropologist Jean-Jacques Iblen of the Collège de France in Paris and the Max Planck Institute for Evolutionary Anthropology in Germany, lead author of the study published in the journal Nature.
"The fossils show a mosaic of primitive and derived traits, which is consistent with the evolutionary differentiation that was already underway at that time, while at the same time confirming the deep African origin of the Homo sapiens lineage," Iblen added.
The oldest known fossils of the species Homo sapiens, around 315.000 years old, were also found in Morocco, at the archaeological site of Jebel Irhoud.
Knowing the age of the fossils from the Grot a Omini cave, determined based on the magnetic signature of the cave sediments that surrounded them, helped researchers assess where this population fits in the family tree of human evolution.
"Determining the age was key to interpreting this material," Iblen added.
The fossils were buried by fine sediments over time, and the entrance to the cave was blocked by a sand dune, which allowed for the remarkable preservation of the remains. Hundreds of stone artifacts and thousands of animal bones were also discovered in the cave, Reuters writes.
The human fossils from the Grot a Ominid cave are approximately the same age as the fossils from the Gran Dolina site near Atapuerca in Spain, which belong to the archaic human species Homo antecessor. These fossils, in fact, share certain characteristics.
"The similarities between Gran Dolina and the Grot a Omini cave are intriguing and may indicate occasional connections across the Strait of Gibraltar, a hypothesis that deserves further investigation," Iblen said.
Hominins from that period had body proportions similar to modern humans, but with smaller brains.
The lower jaw, or mandible, of a child from the Grotta Ominidès cave, about a year and a half old, was completely preserved, while the mandible of one adult was almost complete and the other partial. One of the adult jaws was more robustly built than the other, indicating it belonged to a male, while the other was probably female. The largest fossil was the thigh bone, or femur, of an adult, Reuters reports.
These people were capable of hunting prey, but they navigated a dangerous environment and sometimes became prey themselves, as large carnivores - including big cats and hyenas - lurked in the area.
"Only the femur shows clear signs of carnivore activity - gnawing and tooth marks - suggesting that it was consumed by a large carnivore. However, the cave was primarily a predatory den that was used only occasionally by hominins. The absence of tooth marks on the mandibles does not mean that other parts of the body were not eaten by hyenas or other carnivores," Iblen said.
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