Fascinating, thanks for sharing :) I'm greatly enjoying the figs this time of year, not long ago I started eating them unpeeled, they taste even better. Plus more fiber yay!
It is these gut microbes that convert the fiber in figs into energy. Chilcas, we can infer, depended upon their gut microbes to help them digest their food. They depended on their microbes to help defend them against pathogens. Such microbes helped to keep them alive, and so one might say that they also help to keep the figs around.
Homo sapiens sapiens still works exactly the same way. A common misconception is that (vegetable) fiber doesn't give us energy; not true, our gut flora breaks it down into all sorts of short chains that are consumed for example by our own enteric cells, therefore consuming less of other macronutrients.