Why? Paleolithic area humans may have had a life expectancy of 30-35 but it had nothing to do with diet, it has to do with so many dying as children (obviously not diet related), but once you passed the age of 5 you were generally going to live to your 60’s.
You are making some pretty black and white statements without any evidence to support it but giving you the benefit of the doubt and assuming all that is true, that does not mean that if you eat like them you will live long.
If you really cared to learn about life expectancy of Paleolithic area it’s pretty simple to google, and Where did I claim if you eat like them you will live long like them?
Possibly. On the other hand, it does makes sense to feed animals a diet to which they are evolutionarily adapted. Visit a zoo sometime and ask what each animal eats. They are all feed something intended to be nutritionally similar to their natural diet. Because that’s what works.
I tend to agree that, in many cases, more "natural" is more "healthy" but my main caveats would be:
1. "natural" does not automatically mean better. Depends on the context and many other factors.
2. Determining what is "natural" is also contextual based on what timeline you are talking about and what geographic location. To say "paleolithic ways of eating are healthier" is meaningless unless you think that we a. know exactly what they ate back then and b. every human had access to the same foods regardless of where they lives on the planet