When did ants start cultivating fungus strains?

Ants evolved from wasps some 100 Mya (million-years-ago). But some ants cultivate fungi as cotton-wool-like clumps inside their nests. The notorious leafcutter ants are a good example. They don’t eat the leaves themselves – instead carrying the disk-shaped bites of leaf back to their fungus gardens to feed the fungus. Then they eat the fungus.

Some fungus species are unknown in the wild, having been completely domesticated by their ant hosts. And like a variety of fruit domesticated by humans, the fungus is never allowed to propagate in the natural way (which would give rise to a new and likely inferior variety), but always by taking cuttings. Before the annual mating flights, the young queens are each given a little piece of fungus to kick-off their own culture once they have mated and the newlyweds have established their own nest.

Modern DNA analysis is pretty good at estimating when a species first appeared. Trying to date the appearance of fungus-growing ants gives confusing results, so attention has turned to the fungus strains themselves. Here the results are much clearer: 66 Mya is when the cultivated strains appeared.

Now that’s just about the time of the Chicxulub Event: the dinosaur-killing asteroid strike. By all accounts the earth was a dark, damp and gloomy place after that, for very many years. Perfect weather for fungi.

So, as some might have it, the devastating Chicxulub asteroid was God’s way of teaching ants to farm their own food.