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Genetics is fascinating. It allows us to learn a lot of things about plants and animals that we never would have understood otherwise. Take leaf-cutter ants in the tropical forests of Central America. Every day, they go out and harvest sections of leaves from nearby trees, then return those cuttings to their homes, where they use them to feed a type of fungus that they have had a long, symbiotic relationship with. The fungus, in turn, grows small protein-rich bulbs that the ants digest. Neither of them can live without the other; the fungus needs the leaves to grow, and the ants need the fungus to eat.

That didn’t happen on accident: the ants engineered it that way. About 60 million years ago, some ants gave up the hunter-gatherer lifestyle they had enjoyed and started eating fungus that lived off woody matter. Over time, both started…