Why does the human need meat?

I think you shouldn't. Humans closest relative, the Ape, does not eat other animals, and has a plant based diet. Also the human body's eating tools are not similar to the eating tools of a real meat-eater. Humans today raise animals for slaughter in the most cruel way possible, and process it enough so it is suitable for a non-meat eater (human) to eat, which in the end isn't good for your health anyway.