The costs and benefits of things change over time and hence the stable outcomes can change a lot over time. It's only in the last few 100 years that anything resembling a "job" where you sit at a desk all day existed. 1000s of year so of human evolution is people moving around, people who didn't "simply went extinct under the stress to survive and reproduce that they couldn't compete". Obviously the claim that this means we can't modify this at all is completely ridiculous.