June 13, 2013 – A fossil of the oldest known primate skeleton has been discovered in China's Hubei province, which is not very far from the province where a fossil of the oldest known relative of modern birds was discovered two weeks ago.
But what makes this discovery so important is that it is likely a fossil of humankind's oldest known cousin!
The tiny primate represents genus and species that had not yet been discovered. It has been named the Archicebus achilles from the Greek words arche (meaning beginning or first), kebos (meaning long-tailed monkey). It gets its species name Achilles from the name of a mythological Greek warrior, which also describes its strange ankle anatomy.
This Archicebus achilles fossil dates back to 55 million years ago, and because it is so old it is "the closest thing we have to an ancestor of humans," according to study author Christopher Beard.
Humans are a part of the same order of life as baboons, apes, and monkeys: the primate order. There are three subcategories of primates: one named anthropoids includes humans, apes, and monkeys, and the two others include lemurs and tarsiers.
While the Archicebus achilles was technically a tarsier, showed the beginnings of some human features like forward-facing eyes, nails, and opposable thumbs; this means that it lived around the time when anthropoids and tarsiers started going down different evolutionary paths!
"It represents a big step forward in our efforts to chart the course of the earliest phases of primate and human evolution," said Dr. Xijun Ni of the Institute of Vertebrate Paleontology and Paleoanthropology at Beijing's Chinese Academy of Science.
The Archicebus achilles' body was the same size as a mouse's, making it one of the smallest known mammals. While most mammals today are much bigger if you were to look far enough back into history their ancestors would have been much tinier.
Because the Archicebus achilles was so little and warm-blooded it had to constantly hunt bugs and move around to stay warm enough. It would rarely stand still for more than a few seconds, kind of like someone who is very hyper from eating too much sugar or caffeine!