It was scarce, and starvation was more common threat than diabetes. Also evolution doesn't care if you are happy, healthy, live long, etc. It only cares how go

It was scarce, and starvation was more common threat than diabetes. Also evolution doesn't care if you are happy, healthy, live long, etc. It only cares how good are you at spreading your genes. We only live long because grandparents make kids more probable to live long enough to procreate.