Experience the darker side of evolutionary theory. Jean-Baptiste Lamarck's theory of evolution (you can pass down traits that you pick up during your own lifetime) was largely considered to be completely bogus until some fast-evolving frogs gave it a second wind. Then things got really crazy. Skip ahead to 22:48 for a mind-blowing update to classic evolutionary theory. A rat mother's licking can fundamentally shift the personality of the baby? SCIENCE!