Richard Prum says there's a lot that traditional evolutionary biology can't explain. He thinks a neglected hypothesis from Charles Darwin — and insights from contemporary queer theory — hold the answer. Plus: You won't believe what female ducks use for contraception.

Thomas Hildebrandt is trying to bring the northern white rhinoceros back from the brink of extinction. The wildlife veterinarian tells Steve about the far-out techniques he employs, why we might see woolly mammoths in the future, and why he was frustrated the day the Berlin Wall came down.