Details of tooth shape in the Asian Afrasia and the North African Afrotarsius fossils indicate that these animals probably ate insects. The size of their teeth suggests that in life these animals weighed around 3.5 ounces (100 g), roughly the size of a modern tarsier.
Because of the complicated structure of mammalian teeth, paleontologists often use them as fingerprints to reconstruct how extinct species are related to each other and their modern relatives. These similarities provide strong evidence that Afrasia's Asian cousins colonized North Africa only shortly before the appearance of Afrotarsius in the African fossil record. If Asian anthropoids had arrived in North Africa earlier, there would have been time for more differences to evolve between Afrasia and Afrotarsius. The close similarity in age and anatomy shared by the two species makes Afrasia a touchstone in the quest to date the spread of anthropoid primates from Asia to Africa.
"For years we thought the African fossil record was simply bad," says Professor Jean-Jacques Jaeger of the University of Poitiers in France, the team leader and a Carnegie Museum research associate. "The fact that such similar anthropoids lived at the same time in Myanmar and Libya suggests that the gap in early African anthropoid evolution is actually real. Anthropoids didn't arrive in Africa until right before we find their fossils in Libya."
Implications for future research
The search for the origin of early anthropoids—and, by extension, early human ancestors—is a focal point of modern paleoanthropology. The discovery of Afrasia shows that one lineage of early anthropoids colonized Africa around 37 million years ago, but the diversity of early anthropoids known from the Libyan site that produced Afrotarsius libycus hints that the true picture was more complicated. These other Libyan fossil anthropoids may be the descendants of one or more additional Asian colonists, because they don't appear to be specially related to Afrasia and Afrotarsius. Fossil evidence of evolutionary divergence—when a species divides to create new lineages—is critical data for researchers in evolution. The groundbreaking discovery of the relationship between Asia's Afrasia and North Africa's Afrotarsius is an important benchmark for pinpointing the date at which Asian anthropoids colonized Africa.
"Groundbreaking research like this underscores the vitality of modern natural history museums," says Sam Taylor, director of Carnegie Museum of Natural History. "Research like this can only be sustained by the irreplaceable collections, curatorial expertise, and scientific infrastructure that natural history museums provide. At the same time, cutting-edge science like this revitalizes our museum's educational programs and propels its mission."
"Reconstructing events like the colonization of Africa by early anthropoids is a lot like solving a very cold case file," says Beard. "Afrasia may not be the anthropoid who actually committed the act, but it is definitely on our short list of prime suspects."