The Monkey in the Middle — of Evolution?

The greatest evolutionary discoveries can deal a real blow to the human ego. Case in point: In this week's issue of the journal Nature, scientists introduce Eosimias, which they believe to be the earliest link between the human-ape branch of the Darwinian tree and the branch that tapered off into the cute but inglorious likes of the lemur. So what does our oldest known relative look like? Well, like a very tiny, very delicate monkey — in fact, it's the smallest primate ever found. Bones of the one-ounce Eosimias were uncovered in China during a fossil-hunting expedition, leading scientists to speculate that the evolutionary moment that sparked human existence probably happened in Asia, even though the first humans did emerge from Africa.

Locating these remains was a real coup for anthropologists, explains TIME science writer Alice Park. "Eosimias has been part of the evolutionary equation for some time, but until now, scientists only had dental bones to identify the animal." For identification purposes, and in order to place a species on the timeline of evolution, the most critical bone structure is that in the heel and foot of an animal. And now, with greater number of bones at their disposal, researchers have established that the foot and heel contain what Park calls " a mosaic of characteristics from both higher [humans and apes] and lower [lemur and tarsiers] primates," solidifying the theory that this species represents a rarely pinpointed moment of evolutionary transition. So this particular Eosimias will serve a far more dignified purpose than it once appeared; scientists consider it likely that these remains were rescued from the calcified vomit of a predatory night owl.