When an asteroid slammed into Earth 66 million years ago, it caused a mass extinction. Now researchers have evidence that this catastrophe ushered in the invention of agriculture by ants.
“Extinction events can be huge disasters for most organisms, but it can actually be positive for others,” says Ted Schultz, curator of ants at the Smithsonian National Museum of Natural History and senior author of the paper. “At the end of the Cretaceous, dinosaurs did not do very well, but fungi experienced a heyday.”
What’s the link between fungi and ants?
The researchers propose this anti-culture heyday began with a cataclysmic collision that filled the atmosphere with debris and blocked out the sun, halting photosynthesis for years. As plants died en masse, they littered the ground with organic matter.
Fungi proliferated and ants ate the fungi for food. Some ants continued to eat fungi after Earth’s ecosystems rebounded and today more than 250 ant species have adapted and actively create conditions for fungus to thrive.
“Ants have been practicing agriculture and fungus farming for much longer than humans have existed,” says Schultz.
To pinpoint when this symbiotic interaction began, Schultz and colleagues amassed the largest genetic dataset of fungus-farming ants.
They also analysed the genetics of hundreds of fungi species, including those that are farmed by ants and their wild relatives.
Next, the team assembled evolutionary trees for both ants and fungi which revealed that farming ants and their fungus crops have been intertwined for 66 million years.
The data also revealed that “higher” forms of agriculture, where ants and fungi are completely reliant on one another, evolved around 27 million years ago. This coincided with a rapid global cooling event that fractured tropical environments. These changes led to ants cultivating a fungus outside its natural habitat.
“The ants domesticated these fungi in the same way that humans domesticated crops,” says Schultz. “What’s extraordinary is now we can date when the higher ants originally cultivated the higher fungi.”
Like humans, ant agriculturists have dealt with familiar challenges including the problems with monoculture and the trade-offs of selecting for higher food yields.
“We could probably learn something from the agricultural success of these ants over the past 66 million years,” says Schultz.
