Obviously, the tipping point came when fire was invented. Fire greatly reduced the forces of natural selection by allowing hominids to ward off predators as the latter are afraid of fire.
I don't find the tipping point so obvious. It's hard for me to imagine looking at a bunch of humans, thinking they're "natural," and then all of a sudden one of them is rubbing sticks together and makes a fire and I go "yep there it is, of course they're "unnatural" now." If another species used fire would they automatically become "unnatural?" Some species of pine trees cannot seed unless they are burned by a forest fire. How is the ability for an organisms brain to figure out how to control something like fire different than a dolphins' brains' ability to figure out how to control the sonic energy they can produce to heard fish? Or when apes use sticks to get at insects. How is your brain
not a part of natural selection? Would you not have been
selected out of the gene pool if you were not smart enough to use fire to ward off predators? Is that "unnatural" selection?
I would not consider humans as being "natural". I mean we have birth-control pills, we have cars which make us walk less which explains our modern-day obesity epidemic, we have lights at night which disrupts our natural sleeping-cycles so that many people take sleeping-pills etc. etc.
I'm still waiting for a definition of the word "natural." So sleeping pills are "unnatural," is chewing valerian root to fall asleep "unnatural?" What if the sleeping pills are extracts of that root? At what point is it "unnatural?"
As for walking less explaining the modern day obesity epidemic I'm flabbergasted that you would suggest and/or believe that. Are you claiming you can treat obesity by prescribing walking? Has that study not been done many times with a failure rate of 100%?