I'm a vegetarian.  Do you know the history of vegetarianism? 
From what I know Vegetarianism got it's roots in ancient India and ancient Greece
What vegetables did the people eat during that time? 
Much the same as what we eat today. The concept is not to eat flesh. Some people include dairy and eggs while others don't.
So the practice is pretty much static? Has any advancements been made in it since the inception? 
Other than things like meatless meats it's stayed the same. It's all connected with the idea of nonviolence towards animals. It was originally promoted by philosophers and religions