Your Inner Fish

"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.

"Your Inner Reptile" traces our hair, skin, teeth, jaws and sense of hearing back to reptilian ancestors — from ferocious beasts that ruled the Earth to a little shrew-like animal that lived 195 million years ago.

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.

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.

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.

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.

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.

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.

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.

Our ears are much more sensitive than those of most reptiles, due to the tiniest bones in the human body. But where did these bones come from? Evolutionary biologists Karen Sears and Neil Shubin show us evidence of their connection to the bones of ancient reptilian jaws.

The Bay of Fundy in Nova Scotia, Canada, is home not only to the world's largest tides, but also to some incredibly important fossils. Paleontologist Neil Shubin describes one particularly striking specimen from these cliffs: an animal in the midst of the reptile-to-mammal transition.

The molars, incisors and canines that fill your mouth have a deep evolutionary history. Join paleontologists Roger Smith and Neil Shubin as they trace the history of your teeth back to fearsome beasts that lived over 200 million years ago.