The Genetic Factor
Geneticist Sean Carroll looks at the likely underpinnings of the handwalkers' condition.

The Family and Me
Working with the Ulas family deeply affected psychologist Defne Aruoba.

Origins of Bipedalism
Explore hypotheses for why we stand up, choose your favorite, then hear what paleoanthropologist Donald Johanson thinks.

Compare the Skeletons
The bones of chimps, early human ancestors, and modern people reveal what it takes for us to walk upright.