Our early human ancestors began to walk on two legs a couple of million years ago, abandoning their old life of swinging between tree branches and perching in the leafy forest canopies of Africa. Now, a new study suggests that this transition from the trees to the ground was a long one. It appears that our ancestor A. …

Meet Ida, the 47 million year old fossil who may represent one of our earliest known ancestors. She's probably the most complete primate fossil ever discovered, and she explains where humans (and lemurs) come from.