2017-04-11 20:46:02
Trilobites: How Ants Figured Out Farming Millions of Years Before Humans

20:46, April 11 170 0

We humans think we’re pretty smart because we invented farming. But we didn’t.

In a rain forest in South America millions of years ago, itty-bitty ants with brains no bigger than a pinpoint had already figured it out. They started farming fungus for food — probably not too long after the Chicxulub meteor impact caused the mass extinction event that obliterated up to three-quarters of the rest of Earth’s plants and animals.

Today some 250 species of ants in tropical forests, deserts and grasslands throughout the Americas build fungi gardens in climate-controlled chambers underground. They weed them. They water them. Some even use antibiotics or chemicals to keep harmful bacteria away from their crop. Now scientists have traced the evolutionary history of how these ants became such sophisticated fungus farmers over millions of years in a study published Tuesday in the journal Proceedings of the Royal Society B.

“If you had X-ray vision and you could look out in a wet, new-world tropical forest, you’d see the entire underground just peppered with garden chambers,” said Ted Schultz, an entomologist at the Smithsonian National Museum of Natural History and lead author of the study.

By comparing the genomes of 78 species of fungus farmers, including leaf-cutter ants, with 41 non-fungus farming species, Dr. Schultz and his colleagues revealed curious patterns. They found that fungus-farming ants probably all came from the same ancestor in the rain forests of South America some 60 million years ago. But 30 million years later, two kinds of ant-farming societies diverged.

One contained higher, more complex agriculturalists, which probably transported their fungus with them to dry or seasonably dry climates like deserts or savannas. There, they cared for it in their underground gardens, co-evolving until the fungus became totally dependent on its farmer. The second society was made up of lower, less complex agriculturalists, based primarily in tropical forests, and they grew fungus capable of escaping its garden and living independently.

Dr. Schultz speculated that with enough time, the dry climate created ideal conditions for the more complex ant farmers to domesticate the fungus, controlling temperature by digging deeper chambers, or maintaining humidity by bringing in water from fruits, plants or morning dew. “They’re already kind of putting their fungal crops in greenhouses,” he said, “but if you’re in a dry habitat, even if your fungal crop could escape, there’s nowhere to go.”

Dr. Schultz thinks we can take a lesson from these ant-brained farming methods. An ant’s fungus garden is primarily a monoculture, but the ants can sustain it for about 15 or 20 years. The ants weed out fungi that try to eat what they’ve grown, or chemicals produced by the cultivated fungus kill it.

“These ants have been growing fungi for 55, 60 million years, and this crop disease has been around pretty much since the beginning, and it’s all sort of sustainable,” Dr. Schultz said. “If that were a human in that position, the vegetation for a mile around would be denuded.”