Evolving an ability to run long distances might have been key to survival for early humans. In this podcast, we talked to Dan Lieberman, an evolutionary biologist at Harvard University, to find out why. Podcast produced by David Levin. Original interview by Gaia Remerowski. NOVA is produced by WGBH in Boston. Funding for NOVA is provided by ExxonMobil, David H. Koch, the Howard Hughes Medical Institute, the Corporation for Public Broadcasting, and public television viewers. To learn more, go to pbs.org/nova/becominghuman