Your Inner Monkey

Fossils of human ancestors from millions of years ago can be found in the rocks of Ethiopia. Paleontologist Don Johanson recounts his discovery of one iconic fossil, and the impact it had on our understanding of where we come from.

Because of our evolutionary relationship, we have quite a bit in common with other living primates, including squirrel monkeys. See what we mean as you watch these agile monkeys navigate their forest world.

Unlike most other primates, apes don't have a tail. When did our ancestors lose this potentially useful appendage? Paleoanthropologist Holly Dunsworth introduces Neil Shubin to Proconsul, a fossil ape that provides some answers to that question.

Even though your brain enables you to do some amazing things, its evolutionary story runs deep. Biologists Peter Holland and Neil Shubin go hunting for Amphioxus, a tiny, simple animal, whose genes show us just how ancient our brain truly is.

Our hand has the same basic form as the hands of all other primates. But what did the earliest version of this hand look like? Neil Shubin pays a visit to Jon Bloch, who shows him a remarkable fossil of Notharctus, an early primate with a hand that you may recognize.

When did we start walking exclusively on two legs, and how did this transition take place? Neil Shubin pays a visit to Tim White and Owen Lovejoy, two anthropologists working together to understand "Ardi," a 4.4-million-year-old fossil that sheds light on our transition to bipedalism.

"Your Inner Monkey" tracks our hands, feet, color vision, spine and upright gait to our primate and hominid progenitors, who also passed on perhaps the most important legacy of all: a path to the human brain.

The shape of our backs keeps us balanced when we walk on two legs, but it comes at a cost. Anatomist Bruce Latimer shows how our transition to being exclusively bipedal has led to many common back ailments.