Fifty five million years ago in the palaeocene there lived a small mammal (which is now called Archicebus achilles) in what is now China. It may be this is the earliest known primate and thus the common ancestor to monkeys, apes and us!
Archicebus was rather small, being only 7cm long, and lived alongside tropical lake shores eating insects. The fossils of Archicebus show features now known in tarsiers, early primates which now live in South East Asia. Other features are common in other primate groups.
Near complete skeletons of Archicebus are known which is greatly aiding analysis. Archicebus lived about 7 million years earlier than the previous earliest known primates. Archicebus may also show the divergence point between tarsiers and modern monkeys and apes, a key point in human evolution.