Enough people are living as vegetarians to counter your claim of meat being necessary. Even so, meat consumption per person seems to go up everywhere, so even if you assume people need meat, a century ago they needed a lot less meat per person somehow.
In today's world, vegetarians have access to various non-animal sources of protein that our bodies cannot produce on its own. This has not always been the case. Regardless, the point is our bodies need certain things to be healthy, and those things are historically mainly found in meats and vegetables.
And I won't argue that we eat more meat than our bodies need. But then again, we eat more EVERYTHING than our bodies need. Most of that is likely due to our survival instinct that makes high calorie food taste appealing- protein, fats, and sugars.
