Summer series: Animals teaching us how to love and how to fly

Chris tells us about an amazing new discovery of dinosaur tracks in Britain, then we continue our replay of classic stories from the archive: Catriona shows what we can learn about love and affection from the hormones of monogamous prairie voles, and Chris shares the formula for the frequency of flapping wings to fly, and uses it to calculate how fast a human would need to flap their arms.