Paleontologists digging in the Egyptian desert have unearthed the oldest known relatives of bushbabies and lorises, pint-sized primates that share a common ancestor with humans. The 38-million-year-old fossils fill a major gap in the primate family tree and suggest to some researchers that the earliest human ancestor evolved earlier than is widely thought. They also provide the earliest evidence of grooming behavior in primates.
Pronglike teeth on the lower jaw of lemurs, lorises, and bushbabies form a "toothcomb" that the animals use for grooming. These toothcombed prosimians make up half of the primate family tree, sharing a common ancestor with the other half, which includes humans, apes, and monkeys. When and where the common ancestor evolved is a mystery because so few primate fossils have been found, but most paleontologists place it in Africa around 65 million years ago. However, the new loris and bushbaby fossils, which are about twice as old as the only other fossils of their kind, may push that back.
Erik Seiffert, a graduate student in biological anthropology at Duke University in Durham, North Carolina, and his adviser, primatologist Elwyn Simons, discovered the fossils in the Fayum Depression in the Sahara Desert and they describe their find in the 27 March issue of Nature. The tiny jawbone fragments and teeth represent two new species: the loris Karanasia and the bushbaby Saharagalago. Grooves created by the passage of hairs on the teeth are visible through an electron microscope--indicating that they were used for grooming.
The fossils add weight to other lines of evidence that the primate lineage is more than 65 million years old. Mammalogist Anne Yoder of Yale University says the findings mesh well with her genetic studies, which suggest that the earliest primate ancestor evolved around 70 million years ago. Primatologist Robert Martin of the Field Museum in Chicago has done statistical models that push that date back to about 90 million years ago, while the continents were still shifting. He thinks the next tree-shaking fossil will come from outside of Africa. “I think we may be looking for primate fossils in the wrong places,” says Martin. “The place I would put my money on is India.”