Eating meat was one of the most significant events in human evolution. Meat is a compact source of protein allowing humans not to spend all their time foraging for food, like other grazing herbivores. This lead to the body using more of its energy on its large brain and not so much in its digestive system. Carnivores and omnivores have significantly larger brains than omnivores.
Also, with less time spent eating, human curiousity led them to pursue other things such as the tool making, invention of language and the forming of culture. Meat is directly responsible for creating what it means to be human.
But vegans or vegiterians will argue that in developed countries such as North America and Europe, eating meat is no longer a necessity, unlike food deprived nations in parts of Africa and Asia. North Americans and Europeans have the benefit of having food foraged for them at the supermarket so don\'t expect them to be grazing on your lawn all day.

However, they must eat more often since the plants and vegetables they eat do not stay long enough in their digestive system for the body to absorb all the nutrients. Fortifying their diet with vitamins is sometimes a necessity.
Both omnivore and herbivore humans still indirectly destroy the remaining forests on Earth - for farm space to feed them and the animals they eat.
I like cheese.
