Vegetarians don't consume meat, eggs and dairy are sometimes consumed but not always.
Vegetarians only eat fruits, vegetable we do not eat meat at all because we do not want animals to be killed 
The earliest known examples of vegetarianism occurring is from the 7th century BCE.
Yes we actually have teeth to only eat vegetable the long sharp teeth humans used to have are all gone
There are nutritional downsides to not eating meat, including reduced calcium intake, reduced choline with is needed for brain health and there is an increase in risk of stroke.
This is a discussion that has taken place during decades, because grains and nuts provide all proteins a human need if consumed with carbohydrates and veggie fat
Many people assume if something is labeled vegetarian it is healthier, but that's not always the case, such as soy milk which has way less protein in it than cow's milk.
Moderation is the clue, also quality and what kind of food are you taking, the best food is fresh food, like fresh vegetables fresh fruit, Canned food is not good 
Recent studies have shown that food that is canned retains its nutrients and vitamins.
Those are paid researchers they have a biased point fo view because nothing can be better than not proccesed. We are what we eat