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Machines Like Us

Discovery sheds new light on higher primate evolution

Wednesday, 06 June 2012

Image credit: Pavel Švejnar, via Wikimedia Commons

An international team of researchers has announced the discovery of Afrasia djijidae, a new fossil primate from Myanmar that illuminates a critical step in the evolution of early anthropoids—the group that includes humans, apes, and monkeys. The 37-million-year-old Afrasia closely resembles another early anthropoid, Afrotarsius libycus, recently discovered at a site of similar age in the Sahara Desert of Libya. The close similarity between Afrasia and Afrotarsius indicates that early anthropoids colonized Africa only shortly before the time when these animals lived. The colonization of Africa by early anthropoids was a pivotal step in primate and human evolution, because it set the stage for the later evolution of more advanced apes and humans there. The scientific paper describing the discovery appears June 4 in Proceedings of the National Academy of Sciences.

For decades, scientists thought that anthropoid evolution was rooted in Africa. However, more recent fossil discoveries in China, Myanmar, and other Asian countries have rapidly altered scientific opinion about where this group of distant human ancestors first evolved. Afrasia is the latest in a series of fossil discoveries that are overturning the concept of Africa as the starting point for anthropoid primate evolution.

"Not only does Afrasia help seal the case that anthropoids first evolved in Asia, it also tells us when our anthropoid ancestors first made their way to Africa, where they continued to evolve into apes and humans," says Chris Beard, Carnegie Museum of Natural History paleontologist and member of the discovery team that also included researchers from Myanmar, Thailand, and France. Beard is renowned for his extensive work on primate evolution and anthropoid origins. "Afrasia is a game-changer because for the first time it signals when our distant ancestors initially colonized Africa. If this ancient migration had never taken place, we wouldn't be here talking about it."

Timing is everything

Paleontologists have been divided over exactly how and when early Asian anthropoids made their way from Asia to Africa. The trip could not have been easy, because a more extensive version of the modern Mediterranean Sea called the Tethys Sea separated Africa from Eurasia at that time. While the discovery of Afrasia does not solve the exact route early anthropoids followed in reaching Africa, it does suggest that the colonization event occurred relatively recently, only shortly before the first anthropoid fossils are found in the African fossil record.

Myanmar's 37-million-year-old Afrasia is remarkable in that its teeth closely resemble those of Afrotarsius libycus, a North African primate dating to about the same time. The four known teeth of Afrasia were recovered after six years of sifting through tons of sediment near Nyaungpinle in central Myanmar. This locality occurs in the middle Eocene Pondaung Formation, where the same international research team discovered Ganlea megacanina, an influential fossil described in 2009 that helped solidify the presence of early anthropoid primates in Asia.