Long before human ancestors began leaving Africa, their primate forebears may have arrived there en masse from Asia, some 40 million years ago.
An international team of palaeontologists excavating a rock formation in southern Libya have uncovered the fossil remains of several species of anthropoid primates, the group that gave rise to today’s monkeys, apes and, of course, humans. Their find is published online today in Nature.
A number of previous fossils have pointed to an Asian origin for these primates, but when and how they got to Africa has been in question.
The new fossils are about 38 to 39 million years old, and none of the animals would have weighed more than 500 grams, conclude a team led by Jean-Jacques Jaeger, a palaeontologist at the University of Poiters, France. Their diminutive size fits in with previous research suggesting that early anthropoids started small and eventually evolved ever bigger bodies.
Jaeger’s team was surprised to find so many different kinds of anthropoids at the Libyan site, including one species, Afrotarsius libycus, which they say resembles early anthropoids from Asia. Afrotarsius had previously been considered a member of another primate group called tarsiers, but Jaeger’s team say its teeth look more like those of an anthropoid.
The anthropoids uncovered by Jaeger’s team also suggest that an eclectic group of the animals trekked from Asia to Africa, and not a single lineage that diversified after it made it to the continent. “We think there is a strong wave of migration from Asia to Africa shortly before 40 million years ago,” he says. “Now we have to unravel the details of the migration.”
Erik Seiffert, a palaeontologist who studies early primate evolution at Stony Brook University in New York, calls the find “interesting and important." But he thinks the fossils are about 3 million years younger than Jaeger’s team claim, and he questions whether Afrotarsius libycus is really an anthropoid and not a tarsier.
“I agree that evidence seems to support a dispersal of anthropoids from Asia to Africa at some point in the middle Eocene,” the period between 37-48 million years ago, “but we still don’t know exactly when because there is a big gap in Africa’s middle Eocene record,” Seiffert says.
Image: Afrotarsius (top left), Karanesia (top right), Biretia (bottom left), and Talahpithecus (bottom right), Mark A. Klinger, Carnegie Museum of Natural History