If we all had one nipple, we would have had to have evolved from a species with an even number nipples, which likely means one nipple migrating to the center li

If we all had one nipple, we would have had to have evolved from a species with an even number nipples, which likely means one nipple migrating to the center like a founder's eyes. All of those things we have one of we've had one of forever. Going from an even number of things to an odd number would be a strange trick seldom practiced.