That’s the thing, there was no beginning, for all intent and purposes. You can go back to the point where all mammals’ ancestors were what we would recognise no

That’s the thing, there was no beginning, for all intent and purposes. You can go back to the point where all mammals’ ancestors were what we would recognise now as mice, or even before when they were therapsids, and you would have a hard time recognising a bison in that. Everything you can see in an animal is the result of evolution.