Was it learned by trial & error?
If it was learned, does this imply they had to get it right?
Has there been ant diseases from farming they could have evolved to withstand that we don’t know about?
In: Other
They just started doing it.
It’s likely one or a few of a colony began doing it, then the rest of the colony joined in. Ants can learn from each other, so it’s likely one saw another doing it and thought “I need to help” and joined in until it spread.
Once they started doing it and it was beneficial to the colony, that colony would have an advantage over other colonies in terms of growth and size. Also, ants raid each others colonies when they fight, so other colonies may have found out about what they were doing and it could spread that way.
Eventually over time, it becomes instinctual and all colonies of that species are doing it.
But as with anything to do with evolution, it happened by random chance and was good for the animal.
Latest Answers