are vegetarians more ethical by not eating meat?

[Sal]

Sal...................People have lived and feed on livestock for longer than recorded human history.

That is not really true.
If you would have studied human body seriously you would know that it takes thousand of years for something in the body to change.
Considering that the human body is totally in line with a vegetarian diet (fruit, nuts, grain, vegetable etc) then you would draw that your theory is just a dogma (false true).
Only in time of calamity like the ice age or other disaster humans had no choices but to eat meat, but for ages and ages human were almost completely vegetarian.
You look at the length of the stomach.
Look at the gastric acids.
Look at the teeth.
Look at the alkalinity of the human body compared to the acidity of carnivore.
The stomach of a carnivore animal is about 10-12 times shorter and the reason is that the meat is acidic and tend to putrefy very quickly so has got to go through the stomach fast in order not to cause ulcers or other problems.
For this reason the gastric fluids in carnivore are also much more stronger. (sharks digest bones with no problem)
The teeth are also very different.
While the carnivore have teeth to shred the flesh humans have teeth to crush grains or nuts or to eat fruit.
One day one guy point out to me that also humans got canine so is natural for human to eat meat.
I point out to him that hippos got canine 100 TIMES bigger then humans and yet they are full vegetarian so the reason is not that they eat meat but rather they got canine to scare or to fight possible enemy.
My suggestion to you is ...........DO NOT LOOK AT APPEARANCES BUT STUDY THE SUBJECT IN DETAIL BEFORE YOU MAKE UP YOUR MIND.

You do know that recorded human history, compared to the appearance of the first hominids is like a blink of an eye, right?

Oldest recorded history is probably the ancient Sumerians or proto-Chinese civilizations.

This is besides the point, if you mean when we moved from hunter-gatherer to agriculture, this happened around ~40,000 years ago although that is disputed (might be older, depends on what available data there is, really). People think after we moved to agriculture, we selectively breed animals(chickens, cows, pigs, cats, dogs, etc.) and crops (wheat, malt, pears, apples, etc.) that we found to be beneficial to ourselves, that is something which we know pretty damn well, it's just when it really began that's a bit disputed.

That little conjecture about acids and teeth and whatnot I find laughable, because brown/black bears (to mention two species) eat meat and they don't have such acidic stomachs or remarkably gritting teeth, except for the canine teeth that you also find in humans, because most of them are omnivores, like us. I suspect you found your little story about the acids from some creationist bullshit website, which, ironically enough try to explain away the Eden story that all animals in the Eden parable (which they take literally) all ate grass or some stupid shit.