The discovery of a new fossil primate in Myanmar, formerly known as Burma, illuminates a critical step in the evolution of early anthropoids, which is the group that includes humans, apes and monkeys, an international team of researchers has announced.
It also builds on evidence that anthropoids -- humans' early ancestors -- originated in Asia before migrating to Africa where humans would evolve many millions of years later.
It also helps counter long-held theories that anthropoid evolution was rooted in Africa.
The 37 million-year-old Afrasia djijidae, a rodent-sized monkey-like creature whose fossilized teeth were discovered in Myanmar, which borders India, Bangladesh, China and other nations, closely resemble those of another early anthropoid, Afrotarsius libycus, recently discovered at a site of similar age in the Sahara Desert of Libya, said study leader Chris Beard, head of vertebrate paleontology at the Carnegie Museum of Natural History.
The similarity between the evolutionary first cousins, Afrasia and Afrotarsius, indicates that early anthropoids colonized in Africa only shortly before the time when these animals lived. The colonization of Africa by early anthropoids, he said, represented a pivotal step in primate and human evolution by indicating approximately the time that primates arrived in Africa.
The study by Mr. Beard and an international team of researchers appears today in Proceedings of the National Academy of Sciences.
The big question is how the rodent-sized proto-monkey made its way across the Tethys Sea to Africa -- an island continent at the time. Much larger than the current-day Mediterranean Sea, the Tethys Sea connected the Atlantic and Indian oceans. That means the proto-monkey had to take an epic journey across the sea to Africa, where it found a tropical climate, few predators and a lack of competition from similar animals, among other advantages that prompted an evolutionary star-burst effect that led to monkeys, great apes and humans.
"If that migration event hadn't occurred," Mr. Beard said, "there is no reason to think you and I would be here talking about it. If the Asian monkey hadn't gotten to Africa, there is no reason to think that humans would have evolved. There is no reason to think it would have occurred in Asia."
The Afrasia fossils consist solely of teeth. But several closely, and even exactly, duplicate those of Afrotarsius, which support Mr. Beard's theory that the anthropoid family originated in Asia then migrated to Africa. The similarity of teeth suggests the migration occurred only a short time before these animals existed. Otherwise, the teeth would have evolved differently, he said. Previous fossil finds of earlier anthropoid-like animals in Asia suggests that migration went from Asia to Africa.
Afrotarsius is just one of several anthropoid-like creatures from that period discovered in Africa, and there's no available fossil record to indicate which of the few led to the great apes and humans. But Afrotarsius is in the running.
"Reconstructing events like the colonization of Africa by early anthropoids is a lot like solving a murder mystery that is a very cold case," Mr. Beard said. "Afrasia may not be the anthropoid who actually committed this crime, but it definitely is on our short list of prime suspects."
People long have theorized that human evolution occurred solely in Africa followed by the "Out of Africa" migration worldwide. But long before that happened, Mr. Beard said, his research reveals that anthropoids from Asia had undertaken a historically important "into Africa" migration.