Fossils unearthed in a Moroccan cave offer a precise glimpse into early human evolution, dated to about 773,000 years ago using Earth's magnetic field reversal as a timestamp. The remains, blending primitive and advanced traits, suggest an African population close to the shared ancestor of modern humans, Neanderthals, and Denisovans. This discovery highlights northwest Africa's key role in human origins.
An international team has dated hominin fossils from Thomas Quarry I in Casablanca, Morocco, to 773,000 years plus or minus 4,000 years ago. The site, known as Grotte à Hominidés, preserves a detailed magnetostratigraphic record of the Brunhes/Matuyama boundary, the most recent major reversal of Earth's magnetic field. This natural event provides a global chronological marker, allowing researchers to anchor the fossils with unusual precision for the Pleistocene era.
The remains, found in what was once a carnivore den, include a nearly complete adult lower jaw, part of another adult mandible, a child's mandible, vertebrae, and isolated teeth. A femur shows gnaw marks from carnivores. Analyses using micro-CT scans and shape measurements reveal a mix of ancient and derived features, linking these individuals to populations basal to Homo sapiens and archaic Eurasian lineages.
The discovery stems from over 30 years of Moroccan-French collaboration under the "Préhistoire de Casablanca" program, involving institutions from Morocco, France, Italy, and Germany. The site also holds the oldest Acheulean tools in northwest Africa, dated to about 1.3 million years ago.
Matthew Skinner noted the value of tooth structures: "Using microCT imaging we were able to study a hidden internal structure of the teeth... identifying them as representative of populations that could be basal to Homo sapiens and archaic Eurasian lineages." Shara Bailey added that the teeth retain primitive features, differing from Homo antecessor and indicating early regional differences in human populations by the end of the Early Pleistocene.
Denis Geraads emphasized connectivity: "The idea that the Sahara was a permanent biogeographic barrier does not hold for this period. The palaeontological evidence shows repeated connections between Northwest Africa and the savannas of the East and South."
Jean-Jacques Hublin concluded: "the fossils from the Grotte à Hominidés may be the best candidates we currently have for African populations lying near the root of this shared ancestry, thus reinforcing the view of a deep African origin for our species."
These findings, published in Nature, align with genetic estimates of the last common ancestor living between 765,000 and 550,000 years ago, predating known Homo sapiens remains by about 500,000 years.