New fossil evidence suggests different human origin

Possible human ancestor made perilous trip from Asia to Africa


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If Chris Beard's latest study gets more support from fossil evidence, the seafaring journey of a rodent-sized proto-monkey 38 million years ago could represent the most important adventure in human history -- significantly more important than the voyages of Columbus, Magellan or even Apollo 11.

Back then, a tiny anthropoid, the size of a chipmunk, somehow crossed the massive Tethys Sea from Asia to Africa. The ancient sea that eventually became the Mediterranean connected the Atlantic and Indian oceans, with Africa still existing as an island continent.

Whether the monkey hopscotched island to island, floated on trees or took transport on a portion of land that had collapsed into the ocean may never be known.

But now Mr. Beard, the head of vertebrate paleontology at the Carnegie Museum of Natural History in Oakland, and an international team of paleontologists have found a close relative of the African proto-monkey they found in Africa in 2010, but this one was found in Asia. It indicates that the migration from Asia to Africa of the anthropoid -- potentially human's early ancestor -- occurred about 38 million years ago. It also adds support to Mr. Beard's theory that humans' earliest ancestors originated in Asia, which runs counter to long-held beliefs that human evolution is rooted in Africa.

The team including Mr. Beard originally found the fossilized teeth of Afrotarsius libycus in Libya, within the Sahara. Now they've found six fossilized teeth of a slightly more primitive Afrasia djijidae near Nyaungpinle in central Myanmar, formerly known as Burma.

The teeth, some nearly identical, indicate a close relationship between the species on two continents, which indicates that the species migrated from Asia to Africa a short time before these particular animals existed. In time, on different continents, these two insect-eating species would develop much different teeth. Similar teeth prove they were closely related and not long separated.

The study by Mr. Beard and the research team appeared Monday in Proceedings of the National Academy of Sciences.

The discovery of six of Afrasia's teeth took six years of sifting through tons of dirt in Myanmar.

Early anthropoid colonization of Africa, he said, represents a pivotal step in primate and human evolution by identifying, for the first time, the approximate age of the first primates' arrival in Africa.

When the proto-monkey made its epic sea crossing to Africa, it landed in a tropical paradise with few predators and a lack of competition from similar animals, among many other advantages. The result was an evolutionary starburst that eventually 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."

But Afrotarsius represents just one of several anthropoid-like creatures that existed about 38 million years ago in Africa, and there's no available fossil record to indicate which of them evolved into monkeys, great apes and humans. 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."

Richard Kay, a professor of evolutionary anthropology at Duke University, wrote a commentary about the Beard team's study for the same journal. He said their conclusions are valid, given available evidence.

"Sometimes you can be quite wrong, but you have to go with what you've got," Mr. Kay said, noting the evidence that Afrotarsius and Afrasia are closely related. "It's a reasonable idea and consistent with available research."

He noted ongoing disagreements about whether Afrotarsius was an anthropoid or a tarsier, the latter of which was a primate but not a human ancestor. The Beard team argues that it is an anthropoid.

"It reinforces that hypothesis of an Asian origin, but it's not the golden spike," Mr. Kay said. "We have to get better material both from Africa and earlier sediments in Asia before we can be confident about it. This is closer to absolute, but it's not absolutely tied down."

Fossils from early primates in wet, warmer climates aren't well preserved, so one is lucky to find any fossils, Mr. Kay said.

"This is going to be a long story, and Chris' work generally has advanced the work tremendously," he said. "But we need more advancements in the fossil collections."

science


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