An Asian genesis for our ancestors
In the dry, hilly landscape of central Myanmar lies the Pondaung Formation, a series of geological layers composed of red earth and grey sandstone. These unassuming outcrops hold fossils that question the very roots of our primate family tree. For decades, the consensus was that anthropoids—the group including monkeys, apes, and humans—arose in Africa. The discoveries in the Pondaung Formation, however, provide strong evidence for an Asian origin. The fossils date to the late middle Eocene, approximately 37 to 40 million years ago, predating many of the earliest African anthropoid finds.
The environment at that time was vastly different from today's dry zone. It was a lush tropical floodplain with meandering rivers, a habitat that supported a diverse array of life. The primate fossils found here belong to at least six distinct forms, grouped into two main families: the Eosimiidae and the Amphipithecidae. The first of these primates, named Pondaungia cotteri and Amphipithecus mogaungensis, were identified from fragments found as early as the 1920s. Subsequent expeditions have uncovered a wealth of new material, including more complete jaws and teeth, which allow for a more detailed picture of these ancient animals. One important find, a fossil talus (ankle bone), shows features typical of anthropoids and indicates a style of movement known as arboreal quadrupedalism—walking on all fours in the trees.
A diet of hard knocks
The teeth of the Pondaung primates provide some of the most compelling clues to their identity and lifestyle. One particularly informative species is Ganlea megacanina, named for its massive canine teeth. Heavy wear on the tips of these canines suggests they were not primarily for fighting or display, but as tools. Scientists infer that Ganlea used its powerful canines to pry open hard-shelled fruits to get at the nutritious seeds inside. This specialized seed predation is a behavior seen today in South American saki monkeys, but it has never been observed in more primitive primates like lemurs.
This dietary specialization points to a sophisticated ecological role. The existence of such specialized feeders, alongside other primates with different diets, suggests a long period of evolutionary diversification in Asia. Another important fossil, Afrasia djijidae, has teeth that are remarkably similar to, yet more primitive than, a roughly contemporary African anthropoid, Afrotarsius. The similarity supports the "Out of Asia" hypothesis: a group of early anthropoids migrated from Asia to Africa during the Eocene. This dispersal event, perhaps achieved by crossing the ancient Tethys Sea on floating rafts of vegetation, would have seeded the later evolution of primates on the African continent.