It says in your article that life expectancy at birth was 25 years for hunter gatherers societies. Now that’s in great part due to infant mortality, but where does this lower infant mortality come from? Advanced civilization with doctors, medicines and machines that can keep mothers and babies alive,

Not really, it’s due to healthier moms and sanitation, as evidenced by socioeconomic disparities in infant mortality and higher infant mortality in the U.S. relative to other developed countries.

The U.S. example in particular refutes your “overwork = good” thesis