From water and sewer systems, insulated homes with heating, to refrigeration, mechanized agriculture, food distribution, hot water, and medical devices, engineers have done more to extend life and improve human health than doctors.
Absolutely.
Clean water systems, systems to separate sewage from drinking water, and piping drinking water to homes to improve household hygiene with regular bathing and clothes washing did the most to contribute to the population boom of the early 1900s forward than anything else.
Let’s not forget the residential solid wast removal technician’s (garbage man) contribution to improved health.
Soap? Chemists?
And politicians have clearly done more to kill people, sometimes in mass numbers, damage humankind, and impede progress than any other group.
By far the most important factor in extension of the human life span has been the separation of the human waste stream from our water supply.
The reduction started a number of decades before the germ theory of disease proved why this separation was important.
Plumbers have saved a LOT more lives than doctors ever have.