According to Viva in UK...
One of the most pervasive myths surrounding veganism is the belief that humans are naturally meant to eat meat – that we are evolutionarily adapted to eat and thrive on dead flesh. The evidence presented in these pages knocks this myth firmly on its head. Human beings belong to the primate family and the primate family is essentially a vegetarian one. Our closest living relatives such as chimpanzees and gorillas live on a diet of foods overwhelmingly derived from plants, and we ignore our evolutionary past at our peril. Indeed we are already seeing the dangers of dismissing what evolutionary studies show us we should be eating – plants, not animals – with the growing epidemics of killer diseases such as cancer, heart disease, obesity and diabetes which are now occurring in almost every corner of the planet. 
Have these fools not seen chimp killing other monkeys and eating them? If we are evolved to eat plants, why do we have incisors and canine teeth?
These fools thinks that Vegans do not get cancer, heart disease, obesity and diabetes... Vegans do develop all of these same disease and up to 30% of Vegans are obese. And to be honest... majority of these disease can be associated with process food and junk food.
