Tiny Chinese Primate Fossil Reveals Evolutionary Clues to Origins of Humans and Apes

Our evolutionary history may be getting a bit of a rewrite. Scientists have recently discovered the world's oldest known fossil primate skeleton in China. The findings could have major implications for the study of evolution and how we understand the origins of primates.

The fossil remains were actually unearthed from an ancient lake bed in central China's Hubei Province near the course of the modern Yangtze River. The mouse-sized creature existed about 55 million years ago during the early part of the Eocene Epoch. The climate was much warmer then, sporting "greenhouse" conditions that supported tropical rainforests and palm trees that grew as far north as Alaska. The primate, named Archicebus achilles, probably weighed a little less than one ounce.

"The tiny size and very basal evolutionary position of Archcebus support the idea that the earliest primates, as well as the common ancestor of tarsiers and anthropoids, was miniscule," said Daniel Gebo, an expert on the evolution of body anatomy in primates, in a news release. "This overturns earlier ideas suggesting that the earliest members of the anthropoid lineage were quite large, the size of modern monkeys."

In order to better examine the fossil, the researchers digitally scanned it with X-rays to the highest possible resolution. This allowed them to create a 3-D digital reconstruction of the fossil which they were then able to study in depth. In fact, the scans allowed them to digitally manipulate the skeleton, making it stand up.

The scientists made some interesting finds when it came to the skeleton. Archicebus is about seven million years older than the oldest fossil primate skeletons that have been found thus far. But it's not only the oldest primate; it also belongs to an entirely separate branch of the primate evolutionary tree that lies much closer to the lineage leading to modern monkeys, apes and humans.

"Archicebus differs radically from any other primate, living or fossil, known to science," said Christopher Beard, one of the researchers, in a news release. "It looks like an odd hybrid with the feet of a small monkey, the arms, legs and teeth of a very primitive primate and a primitive skull bearing surprisingly small eyes. It will force us to rewrite how the anthropoid lineage evolved."

Finding this fossil, in other words, is huge when understanding how primates evolved. The evolutionary relationships among primates and their potential relatives, and among the major lineages within the primate order, have been debated intensively for many years. Now, scientists may be one step closer to discovering a common ancestor to these primates.

The findings are published in the journal Nature.

Want to see a video of the reconstructed primate? You can check it out below, originally appearing here.