The geography of human origins is changing, with the discovery of 773,000-year-old fossils in a Moroccan cave that pinpoint the beginning of the modern human lineage in northwest Africa, according to a new study.
In a study published in the journal Nature on Wednesday (7 January), a team of Moroccan and French researchers detailed an analysis of a small number of bones believed to represent the last common ancestor of modern humans (Homo sapiens), Neanderthals and Denisovans.
Researchers discovered the fossils in a cave called Grotte à Hominidés (Hominid Cave) on the Thomas Quarry I site in Casablanca, Morocco. The bone consists of three partial lower jaws, several vertebrae, and a number of individual teeth, all of which share some characteristics of Homo erectus but also have characteristics that differ from this hominin’s ancestor.
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Additionally, there were numerous stone tools at the site, and a single leg bone suggests the hyena may have been feeding on hominid animals. By examining the magnetic properties of 180 sediment samples taken from around the fossil, researchers found that the sequence spanned the reversal of the Matsuyama-Brunges magnetic field, a geological event that occurred 773,000 years ago.
The new discovery fills a major gap in the African human fossil record, which spans from 1 million to 600,000 years ago, study co-author Jean-Jacques Hublin, a paleoanthropologist at the Max Planck Institute for Evolutionary Anthropology in Leipzig, Germany, told Live Science via email. Genetic evidence suggests that the last common ancestors of modern humans, Neanderthals and Denisovans, lived in Africa during this period.
Havlin and his colleagues believe the Thomas Quarry fossil is the best candidate for the “roots” of an ancestral tree that connected our species and its ancient cousins.
Although the early chapters of the story of human evolution occurred in eastern and southern Africa, the last million years of human evolution have been complicated by the tendency of our ancestors to wander across Africa and Eurasia.
After H. erectus evolved in Africa about 2 million years ago, some groups spread eastward, reaching as far as Oceania. But other groups stayed there, evolved further, and spread to northern Europe about 800,000 years ago. The group from Spain is known as the Homo ancestry and is most likely the direct ancestor of Neanderthals.
The newly analyzed Moroccan fossils date from about the same time as the H. ancestor, share some distinctive features, and “may reflect a discontinuous connection across the Strait of Gibraltar and merit further investigation,” Hublin said. However, the Thomas Quarry fossil is distinct from both H. erectus and H. antecessor.
“This supports a deep African origin for Homo sapiens and argues against the Eurasian origin scenario,” Hublin said.
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Havlin said further research into North Africa’s extremely rich fossil record is needed to expand our understanding of human origins, which is primarily based in eastern and southern Africa, especially since the clearest early evidence of Homo sapiens comes from the 300,000-year-old site of Jebel Irhoud in Morocco.
Focusing on this geographic region may reveal new clues about the split between our species and its Neanderthal and Denisovan cousins.
“Although we cannot argue that the emergence of the lineage leading to Homo sapiens occurred solely in North Africa,” Hublin said. [new] Fossils from Morocco strongly suggest that there was a population there at the time that was close to the divergence between the Homo sapiens lineage and the lineage that led to Neanderthals and Denisovans. ”
John Hawkes, a biological anthropologist at the University of Wisconsin-Madison who was not involved in the study, agreed with the researchers’ conclusions.
“It’s clear from the new research that these fossils don’t easily fit into variations of Homo erectus in some sense,” Hawkes told Live Science. “They are probably close to the common ancestor that gave rise to Neanderthals, Denisovans and modern humans.”
But it’s unclear what to call the Thomas Quarry fossils. “The way I think about it, these may be the oldest fossils that we can really call Homo sapiens,” Hawks said.
Havlin is hesitant to classify the fossils as a specific species or population, especially since there are only a few fragmentary fossils from the Thomas Quarry. “A paleoproteomics analysis is planned and could help elucidate the relationships between European and North African fossils,” Hublin said.
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