Oldest primate fossil sheds light on our ancestors

The 55 million-year-old fossil, dug up in central China, is one of our first primate relatives, and it gives scientists a better understanding of the complex evolution that led to humans.

This tiny monkey-like creature weighed 30 grams or less and was not a direct ancestor. Because it is so far back on the family tree, it offers the best clues yet of what our earliest direct relatives would have been like at that time, according to a study published Wednesday in the journal Nature.

"It's a close cousin, in fact," said study author Christopher Beard, curator at the Carnegie Museum of Natural History in Pittsburgh. He said it is "the closest thing we have to an ancestor of humans" so long ago.

Primates are the order of life that includes humans along with apes, monkeys, and lemurs. Humans are set apart from other mammals because of their grasping five fingers and toes, nails and forward-facing eyes. And this new species fits right in, Beard said.

The new species has been called Archicebus achilles, a compound name that means "first long-tailed monkey." The "achilles" is derived from the mythical Greek warrior due to its unusual ankle anatomy.

There are three primate suborders: anthropoids, which include apes, monkeys and humans; and two suborders that include lemurs and tarsiers. This new species is in the same grouping as tarsiers, but close to the offshoot branch in the family tree where humans come from, and has anthropoid-like features.

Because it was so small and warm-blooded, it had to eat bugs and move constantly to keep from losing internal heat, Beard said. That means our earliest primate relatives were "very frenetic creatures, anxious, highly caffeinated animals running around looking for their next meal." They lived in a tree-lined area near a Chinese lake, swinging around the forest in a hotter climate.

The study also bolstered a theory that early primates first developed in Asia.

"Recent paleontological advances have really indicated that the first and most pivotal steps in primate evolution, including the beginnings of anthropoid evolution, almost certainly took place in Asia, rather than Africa, which is the received wisdom that we all thought roughly two decades ago," Beard said.

Early anthropoids migrated to Africa during the Eocene, reaching it around 38 million years ago, eventually providing the source material for hominids, he theorized.

The big moment for us was when apes and humans in Africa diverged into separate lineages between 5 million and 10 million years ago.

Source: JapanTimes (JiJi)