We know why sunglasses are important. They block UV rays from the sun, which can damage our eyes and cause cataracts and cancer. However, some people out there actually claim that our cavemen ancestors never wore sunglasses and therefore sunglasses are useless.
This example perfectly illustrates the naturalistic fallacy. Just because something happened in nature or just because our cavemen ancestors did something, it doesn't mean we should.
Cavemen don't drive cars, use smartphones, drink espresso coffee, or wear sunglasses. Does that mean we should not?
Not having access to modern technology, medicine, and science, cavemen on average only lived to about 40.
If we emulated the caveman lifestyle, we wouldn't live long. We would also walk around wearing little clothes and we would smell bad.