Read this interesting article questioning what would happen if the human race turned vegetarian / vegan. This is not to say I am one, though I try to eat less meat, but it would have both positive and negative consequences. At present it is simply unrealistic but it seems to me that eventually, perhaps some centuries into the future, we will be viewed in the same way we view cannibals today.
What Would Happen If the World Suddenly Went Vegetarian?