Off the coast of Sao Paulo lies Ilha da Queimada Grande, an island so dangerous the Brazilian Navy forbids anyone from setting foot on it. Known as Snake Island, this 106-acre rock is ruled by the golden lancehead pit viper, a species found nowhere else on Earth. This episode is a real-world study in rapid evolution and an ecosystem preserved by its own lethality.

We explain how rising seas at the end of the last Ice Age cut the island off from the mainland, trapping snakes in an evolutionary escape room with no ground prey. We explore how the golden lancehead adapted to hunt birds, why it preys almost exclusively on just two of 41 visiting species, and how that hyper-specialized diet makes it critically endangered.

• The harsh, swinging climate and varied terrain of the tiny island
• The failed banana plantation whose slash- ...