I do also realise that as cavemen (Sorry Christians), before we were even able to harvest grain crops, we ate an eqivilant diet to Atkins.... but we don't actually know what long term effects that diet had on our bodys as the life expectancey would have been around 20 back then.

Also you may be interested in looking up the diet of the Hunza people from the Himalayas. They are considered to be the healthiest people in the world with some people reaching ages of 120 up to 140 years of age (apparently) and having near zero intance of cancer. Their diet consists of around 40% calories from whole grains, 30% calories from vegeables, 15% from fruits, 10% beans, 4% nuts/seeds and only 1% from animal products