Anatomist Alice Roberts charts how the hunt for food down the ages has affected the way people look and behave today. A lion kill reveals how similar today's diet is to that of 1.7 million years ago and the origin of marriage is traced back to the Hadza tribe of Tanzania, hunter-gatherers who have been forming long-term couples for 10,000 years. Plus, a skateboarding experiment proves men cannot help showing off to attract the opposite sex.