Wild & Weird: Animal Facts

In 1930 Ronald Fisher claimed the speed of evolution could be read off a single number, and this episode follows that number down into the arithmetic breeders and geneticists still use to predict what selection can and can't change.

Why 'survival of the fittest' points at the wrong scoreboard, and how biology actually keeps score: in copies left behind, averaged across a kind, and sometimes counted in somebody else's young.

Darwin said a peacock feather made him sick, and Ronald Fisher's explanation of that tail turns out stranger than beauty: a taste and a trait that get inherited together and keep pushing each other until the cost of carrying it stops them.

Female animals from crickets to tortoises don't just store sperm after mating; they sort it, favour some of it, and decide which male fathers the next egg, while the males evolve spines, chemicals and stranger tricks to fight back.

Women at peak fertility mark other women down without noticing, and the gossip, the heels and the rumours all come out of the same old contest over who gets a mate.