Jimmy Doherty endures having electrodes put on his face to induce a smile, places a snake in a box inside a monkey's cage and plays the bassoon to some earthworms, as the series recreating some of Charles Darwin's groundbreaking experiments concludes.

Jimmy Doherty continues to work his way through Charles Darwin's series of experiments that formed the basis of On the Origin of Species, like feeding human urine and sausage to Venus flytraps to see which the plant prefers. Some experiments are more tricky, though, requiring Doherty to catch a peacock or fiddle about with a flower's stamen and pistil. Interestingly, it seems that Darwin had a personal reason for investigating the problems caused by interbreeding. He was married to his first cousin Emma (not the only cousins within their families to marry) and was concerned that this was the reason three of his ten children died at an early age.

When Charles Darwin set about proving his theory of evolution, he had none of the advantages of modern genetics or DNA analysis so he came up with some ingenious experiments of his own. In this series, Jimmy Doherty recreates many of these investigations. Jimmy takes a hands-on approach as he digs up a patch of turf in Darwin's own garden in Kent to illustrate the struggle for existence; he ropes down a chalk cliff to explore the age of the Earth; and he lets seeds soak in salt water for a month. The smelly results from this experiment prove that plants have the potential to cross oceans.