Hominin fossils from Morocco may be close ancestors of modern humans

Fossils almost three-quarters of a million years old, discovered in North Africa, could belong to a common ancestor of Neanderthals, Denisovans and modern humans who lived shortly before the three hominid lineages split.

The last common ancestor of modern humans, Neanderthals and Denisovans, are thought to have lived between 765,000 and 550,000 years ago. But exactly where and when he lived remain two of the big questions of human evolution.

The new fossils may not be the last common ancestor of the three human species, says Jean-Jacques Hublin of the Max Planck Institute for Evolutionary Anthropology in Leipzig, Germany, but they are certainly close to the point where ancient human lineages diverged.

Hublin and his colleagues analyzed several fossils found in a cave called Grotte à Hominidae on the outskirts of Casablanca, Morocco, including two adult jaws, a child’s jaw, and several vertebrae. One of the adult jaws was reported in a previous study in 1969, but the others were first described.

The fossilized molars are similar to those of the first Homo sapiens and Neanderthals, but the jaw shape resembles that of older African humans, such as Homo erectus.

Fortunately for scientists, Moroccan hominids lived around the same time as a change in the Earth’s magnetic field, recorded in the geological layer in which the fossils were found, allowing them to be dated to around 773,000 years ago.

Hublin says these discoveries fill a “major gap” in the record of African hominids between 1 million and 600,000 years ago. Paleogenetic studies indicate that it was around this time that the ancestors of Neanderthals and Denisovans split from the lineage that led to H. sapiens. Neanderthals dominated Europe for hundreds of thousands of years. The Denisovans traveled to East Asia and H. sapiens they are thought to have continued to evolve in Africa.

The newly described fossils were close contemporaries of a Spanish population of hominids called Homo ancestor, which has previously been considered a possible common ancestor between H. sapiens and the Neanderthals.

Both H. ancestor and Moroccan hominids exhibit a “comparable mosaic of primitive and derived traits,” says Hublin, meaning there may have been connections and genetic exchange between populations across the Strait of Gibraltar. However, there are also clear differences between fossils from the two regions, with the Spanish fossils more closely resembling those of Neanderthals.

“The last common ancestor of these lineages was probably present on both sides of the Mediterranean at that time and was already diverging,” explains Hublin. “This supports a deep African ancestry for Homo sapiens and argues against the scenarios of Eurasian origin proposed by certain authors.

Julien Louys of Griffith University in Brisbane, Australia, says he is struck by the differences in physical characteristics between early Pleistocene hominids that are closely related or ancestral to our own species.

“The important point being made is that these differences appear to have appeared before Homo ancestor arrived in Spain, implying that this species was one of several species that potentially appeared in North Africa, but then crossed the strait in some way,” explains Louys.

Chris Stringer of the Natural History Museum in London says a study of Chinese hominid fossils published last year, to which he contributed, suggests that the last common ancestor of H. sapiensNeanderthals and Denisovans could have lived more than a million years ago.

“It was not clear on which continent this common ancestor lived,” says Stringer. “However, even though the last common ancestor lived outside of Africa, our analyzes indicated that the subsequent evolution of Homo sapiens always took place in Africa, so in this case there would have been early migration to Africa to continue this evolution.

New Moroccan fossils could even represent a start sapiens ancestor in Africa, he says, but there aren’t enough skeletal pieces to assign it to a species.

He wants to compare the new fossils with those he has already studied to determine their place.