Paleolithic man is genetically the same as modern man. I’m quite sure we’re not extinct.
And they died young due to infectious disease and injuries that were fatal in societies without hygeine or modern medicine. What they didn’t die of was heart disease, cancer, Alzheimer’s, bone/joint diseases, or any of the various other health problems that are the major causes of premature death in the Western world. The ones who didn’t die of infection or injury commonly lived into their 80’s or later, without the benefits of modern medicine. This has been borne out by studies of primitive tribes who were never exposed to modern foods and ate hunter-gatherer diets. Interestingly, when members of those tribes did start to adopt modern agriculturally-based diets, they started to get the kinds of diseases that are the major killers in modern societies.
Yes, I’ve been Paleo for about six months, after over a decade of yo-yo dieting with traditional wisdom low-fat and low-cal diets. I’ve lost a ton of weight, don’t miss bread, rice, potatoes, etc. at all, and my blood work is continuing to improve. (If you have high cholesterol, you need the Lipoprofile test to differentiate the sizes of your LDL particles - only those of a certain size are related to heart disease, but this isn’t yet a commonly ordered test.) I can’t recommend Paleo highly enough, and while Taubes and Atkins aren’t quite the same, they’re very similar and equally far from the terrible USDA-recommended diet.
I recommend that you go on a well balanced diet that includes the Recommened Daily Intakes of carbohydrates, fiber, lipids, protein, and vitamin and minerals. I've been on such a diet for 3 years. It's easy to maintain because it doesn't have the monotonousness of these fad diets like the paelo diet, and it has long-term health benefits, unlike these short-term, loose-weight-quick fad diets like the paelo diet. Since I've adopted the well-balanced diet, I dropped from 220 to 185. With this diet, combined with a rigorous powerlifting program, I can deadlift 450 lbs at 185. Since I'm a powerlifter, I like to utilize simple carbs for energy and to restore my glycogen post workout. And I use complex carbohydrates for better digestion since I use the upper end of the the RDI's protein intake of 35%.