Because the fossil indicates that the tarsier and anthropoid primate groups split before that era, the anthropoid lineage is also at least that old, says Beard. He says that he and others had suggested a tarsier/anthropoid split of about this time previously, but based on thinner evidence.
Its long hindlimbs and grasping feet suggest that A. achilles lived in trees, with a tail thought to be at least twice its body length helping it to maintain balance as it leapt from branch to branch. The moderate size of the primate’s eye sockets hint that it was active in the day.
The size and shape of the primate's teeth — particularly the sharply pointed premolars, which were well adapted for shearing prey — strongly suggest that the tiny mammal fed mostly on insects. Such prey would have been abundant, because A. achilles evolved during an era when global temperatures were exceptionally high and jungles stretched as far north as the Arctic. “It was a great time to be a primate,” says Beard.
Because A. achilles sits near the base of the tarsier family tree, scientists say it probably resembles the yet-to-be-discovered creatures that lie at the base of most primate groups — including the anthropoid lineage that ultimately gave rise to humans. “If you retrace primate evolution to its beginning, [A. achilles] is what our ancestors most likely looked like,” says Luo.