Nowwww....as with so many other statistics-turned-truisms, that one is also false. Sure, you had a much greater risk of not making it TO 20, but if you did, your life expectancy was actually pretty darned good!
Not into this Paleo crap at all. It's like that Blood Type nonsense. Somebody capping on pseudoscience for fun and personal profit, lots of other herd mentalities hopping on the clown bus.
I do actually like the concept of studying what is most natively advantageous to humans. After all, we developed in just such climes, or we wouldn't be here to argue about it today. We don't keep goats in the basement, monkeys in zoos, or snakes on planes. Uhhhh, mostly. Anyway, we take out hints from how other species do in their native habitats. And those ideas as they relate to humans could tell us a lot about where we're blowing it today...buttttt, you'd have to really study it, right? Not infomercial pretend stuff.
The Human Diaspora apparently took people to live in climates and under conditions that I would personally still find intolerable. (IMHO, YMMV.) But if, as some study shows, our ancestors were indeed swimming apes living on a coast? Hey now! Everything we like to believe about idyllic times on a tropical beach? Yummay. Natcheral. Permanent vacay. Fish, fruit, easy good times. And we like it, because....why wouldn't we?
So, you can celebrate all our 'brave' and 'adaptable' and 'adventurous' qualities all you like. But I'm still gonna see those as excuses for most of the truly epic dumb stuff talking monkeys do, rather than things we should hand out trophies for. The really important thing is, would that beautifully-tanned example of a paradise-dwelling being still go for Nutella? And I think we all know the answer to that!