I am just gonna say this shit once: Humans are not supposed to be vegan.
I already hear the vegans foaming at the mouth over that fact. It's true nonetheless.
"But Juan," I can hear them typing. "Veganism is good for you because animal fat clogs your arteries, it's cruel to kill animals for food, and we don't need to eat any more!" Calm down, Vegan Vilma. I am gonna explain WHY humans aren't supposed to be vegan. And it all goes back to biology.
Humans are omnivorous in nature. According to John McArdle, Ph.D, "The key category in the discussion of human diet is omnivores, which are defined as generalized feeders, with neither carnivore nor herbivore specializations for acquiring or processing food, and who are capable of consuming and do consume both animal protein and vegetation. They are basically *opportunistic* feeders (survive by eating what is available) with more generalized anatomical and physiological traits, especially the dentition (teeth)." Humans have both molars and canines, which means that we as a species, we have evolved to tear meat (with molars) and chew plants (with molars).
Not only this, but look at what vitamins we need for survival. According to Zoologist Matan Shelomi, "Chemically, we lack cellulases or cellulosic symbionts that many herbivores have, and have lots of proteases that carnivores do. But we do have sucrases that let us digest fruits. Humans require vitamin B12 to thrive, which can only come from animal sources or certain bacteria (vegans must supplement their diet). We also require vitamin C, which is present in citrus fruits and organ meat, the latter probably being our evolutionary ancestor's main source. Interestingly, we have very powerful livers (the detoxification organ) and a very strong ability to smell rot/decay/decomposition relative to other animals. This suggests we may have evolved as scavengers, eating dead (but not too decayed) carcasses killed by other animals."
My final point is the most simplest one: Chimpanzees, our closest biological relatives, are omnivores in nature.
So, yeah. Humans are omnivores.