These questions got me thinking.
1. I have no idea of the average life expectancy but I would be willing to bet that the major causes of death were less likely to be diet related (unless you include starving, hunting accidents or becoming someone elses dinner)
2. This question is largly irrelevant considering pretty much all current cultures eat a large amount of carbs. But one thing they have in common is that the chance that they were killed directly by their diet is more common than ever.
Now the big question is why is this the case? We are conditioned to believe its because of a high animal product diet but there is pretty much no correlation between saturated fat and heart disease
But I do still think that the benifits of 0 carb diet need to be questioned because as others have stated even though it is probably extremely close to our natural diets animal products have changed since domestication and I dont want to give up my broccoli, caulifower, lettuce or tomatoes.