Meat consumption natural for humans?

With having a vegetarian in my family, I know how difficult it is for them and vegans to receive adequate amounts of protein, which is typically consumed through meat. I believe since humans for thousands of years have ate meat, it's natural for us now to consume it as well. Whoever began this meat eating trend must have had some natural desire and instinct to think of digesting another animal. Whether it was due to starvation and crazed drive to kill something or the "I can, so I will" stand of humans, something lead us to where we are now.