How Many Chickens Do We Need?

If one chicken isn't enough to say that we have chickens, then how many chickens do we need? What you need for chickens is the chicken species to have arise. Only when we have a separate chicken population can we really say that we've got chickens. So where did the eggs come in then? This speciation event might happen outside the breeding season and there'd be no eggs around at all. I don't think ancestral chickens would have laid eggs every day. That would just mean you had a kind of freaky guinea fowl.