Anthropologists have shown that the advent of human farming was approximately 10,000 years ago in the Middle East. Farming, however, actually originated 40,000 years prior to this – in ants!
The leaf cutter ants are common species tropical rainforests. You first see them when you notice a parade of fingernail-sized leaf confetti moving steadily down the path. The 2-3 inch wide path itself is a moss and debris-free ant highway. Upon close examination, you see tiny red ants clasping bits of leaves above their heads moving in one direction, while leaf-free ants scurry in the other. In some cases even smaller ants piggy-back on the leaf bits to clean and protect the precious cargo in transit.
So what is so special about this? Seeing ants foraging is not unique. Any picnic-lover has watched ants carry off potato chip bits or crumbs of sandwiches.
But unlike picnic-crashers, these ants aren’t collecting leaves for food; they are collecting leaves to feed their fungus. In many-chambered underground nests, the ants grow fungus in a giant farming operation. The leaf pulp (chewed up by the ants) is used as the base to grow the fungus.
“But wait, the human farmer might say. “I spend a ton of time doing a lot more to crops than just fertilizing them. I have to harvest, weed, apply pesticides, and save seeds for next year.”
Yep, the ants do that too.
The ants harvest fungal fruit (hyphal fruiting bodies) from their fungal gardens to feed the colony and the larvae. They weed through fungus crops to get rid of waste and parasitic mold, which they take to special earthen rooms at the edge of the farm, their trash piles. They apply antimicrobial compounds to the fungus to inhibit diseases. And when they move out of their current many-roomed colony, the ants carry spores from their fungus crop and cultures of their antimicrobial compounds.
Leaf cutter ants and their fungi are a classic example of coevolution – how different critters of all sizes and stripes have changed together throughout time. Coevolution is interesting because it helps us understand more about species and how they interact with each other.
Graduate Field Course in Tropical Biology 