Amish friendship bread itself can be regarded in almost purely Darwinian terms. A perfect example of co-evolution, where two widely-divergent organisms evolve together in a symbiotic fashion that benefits both Amish culture, and the cultures in the bread dough.
Within the bread dough, the yeasts reproduce primarily asexually by budding - and one could look at the larger collective of the dough itself as reproducing asexually, by a sort of macro-mitosis if you will (if only metaphorically). The dough is taken to a new host family, they enlarge it by mixing in additional dry and wet ingredients, and after the resultant body of dough has time to fully ferment, it is "split" into new dough "cells" - to be baked as loaves, or to be forwarded on to the next friend. All the while this is going on, the Amish themselves are reproducing sexually by ordinary means (these means perhaps assisted by the natural mixing and leavening effect from the social interaction the bread affords!).
Side note: some claim that the Amish have nothing to do with this bread at all. I'll believe that when I see it with my own eyes.