The whole premise is flawed and appeals to "nature" are a continual sham to sell people diet fads with at best no effect on health and at worse serious negative effects.
The whole appeal to "natural" is so ludicrous. Nothing we do is natural. Our food is either largely engineered or at the very least, bred selectively for maximum harvests. We can arbitrarily decide to travel thousands of miles from our "normal" habitat and be completely confident we will not only survive, but we do this for recreation. Hell, even the meat these weirdos are obsessing over is the result of millennia of selective breeding for the most meat per animal, and even some genetic engineering which is why factory-farmed chickens have tits so big they can't stand up correctly.
"Natural." I challenge anyone to find something in their home that is actually 100% natural.
Not only ludicrous but also frequently used to prop up all kinds of biases.
Evolution of humans is still happening. It's determined by how many of your children survive long enough to reproduce. If you don't have children, for whatever reason, your DNA is edited out of the future.
The factors that drive this have certainly changed over the centuries, but they're always going to be in play (until people are able to customize DNA).
See the movie "Idiocracy" for one take on this.
Replacing MtDNA with that of a donor is already a thing. We are also screening embryos' genes for diseases. Neither of these are true arbitrary-write modications I guess, but we are getting there one step at a time.
The interesting thing is I doubt humans will do well living on other bodies in the solar system without deliberate genetic modification. The modifications would be things like being able to tolerate different gravities, different gas pressure, different air composition, radiation hardening, maybe seeing different light wavelengths, tolerance for various poisonous chemicals, etc.
This is very true and even experts with good communication skills fall pray of perpetuating this misconception.
It's because of all the synergies that emerge in nature, it gets so tempting and to explain these as if they happened through intention. "This butterfly has a pattern that looks like the pattern of trees that grow in it's habitat so it will blend in and avoid prey" sounds so much more like a good argument than "The random mutations in the patterns of these butterflies over time that made them stand out more probably made them easier pray, so survivors would be those that were best at hiding so over time with that selective pressure we are now seeing butterflies that blend in well with the trees, even though they where never at any point able to look at a tree and go 'I want to look like that'".