Seems like a weird idea to me, basing a plan for healthy living on an idea of what things were like when average life expectancy was around 30 - 35 years.
The increase in life expectancy is more to do with the advent of modern medicine, think antibiotics, surgery, greater understanding of proper nutrition.
The reality of paelo is that our physiology has evolved over 100,000 (and in terms of microevolution, 1000's) of years to eat very specific foods, so why mess with it. You take a cave man, treat his diseases, ensure he's never starved, but equally still has to work to earn his keep and you will have a very healthy and long living human being)
That said, we can manipulate of our physiology by eating unnatural and tailor made foods to enhance our performance in certain situations, and I see nothing wrong with that. But when it comes to the majority of your diet, you shouldn't be eating processed crap. Stick to your meats, fruit, veg as well as natural nuts seeds and other natural products and you have the key to a very healthy diet.