Are humans naturally carnivores, herbivores or omnivores?
Humans are evolved to be omnivores. It is possible for a human to be a strict herbivore, but it needs to be done very carefully to ensure that the correct balance is maintained, which is not easily achieved in the wild. Specifically, changes in diet to include fish and meat are thought to have underpinned a sudden increase in brain size in our ancestors (in evolutionary terms; we're talking over many tens of thousands of years). We can actually see from analysing the teeth of very early hominids that the teeth involved in processing plant material are reduced throughout human evolution. Part of the story of becoming human was the story of eating more meat. That said, our teeth are pretty wussy compared to most carnivorous (or even omnivorous) animals - rather than being an indication that early humans lived in some kind of idyllic forest eating fruits and berries, this actually probably reflects the appearance of technology. If you can make a flint knife to strip the hide of a carcass, you no longer need the big canine teeth. If you can cook the meat on a fire, you no longer need the powerful biting jaws of other carnivores. That said - and I absolutely can't stress this enough - that doesn't tell you anything about what we should be eating now. This is neither an argument against veganism, or in favour of meat - simply a rejection of a spurious set of arguments about what early humans were like. This is technically called "the naturalistic fallacy" - even if it were true that our ancestors ate less meat than we do (and they didn't, actually), that doesn't actually have any bearing on how we should behave now. You can't get an "ought" from an "is" as the saying goes. There is an ethical dimension to our food, and we should consider that when we choose our diet. There is a health dimension to our food (eating meat to the exclusion of vegetables is probably more harmful than eating vegetables to the exclusion of meat), so we should take that into consideration too.
Ok so some vegans claim humans are herbivores?
Because we are herbivores. Just because we "can" eat meat doesn't mean that we should or we are supposed to. Our teeth are more similar to herbivores than omnivores. Our "canine" teeth are "canine" in name only, and even some herbivores have very large "canines" that are used for defense purposes. Humans being able to eat meat in no way makes us omnivores any more than a cat eating grass makes them omnivores. True omnivores will thrive eating meat, and it is obvious that the regular consumption of meat makes us sicker. EDIT: I said it was a good read, and he does in fact credit all his sources. But I find it funny that you assume everything he says was false as he does not have a degree, yet you do not need one yourself to prove the contrary.
Are humans omnivores carnivores or herbivores?
We wont get ill if we only eat one kind of food but a lack of meat will impact you physically. though your last point does make sense it doesn't really matter, carnivorous animals are generally more intelligent than herbivores because they need to work out how to kill and humans are born omnivorous and also to people stating that humans are they most intelligent is wrong, we are the most technologically advanced thing to live on Earth but we are not even close to being the smartest thing on earth. in generally we are quite weak (if you don't include weapons made in an unnatural way, so things like guns) even with weapons we could have made such as wood, stone and bone weapons as well.
What proof is there that humans are naturally omnivores?
TECHNICALLY you answered your own question when you said that we are "traditionally" omnivores. By tradition. If those three are the choices then we are traditionally omnivore. The problem is that many of these questions only give 3 choices. Carnivore, Herbivore, and Omnivore. Thats not a scientific question. Zoology defines many variations of "vores" including those and also nectarivores, piscivores, insectivores, granivores, frugivores, and faunivores just to name some. Technically pre-humans were frugivores (fruits and nuts). And then humans became more ground-dwelling and evolved into faunivores. Faunivores diets extended to include vegetables, some grains, honey, insects, fish, birds, eggs and SOME meat. Red meat was usually carrion (rotting meat). That softens it and breaks it down to something that needs smaller canines and intestine to process. Luckily we now achieve the same thing by cooking our meat. You did have the facts correct. But then the problem is that they tend to work for any of them if you limit the choices. We cannot be carnivores without processing our food. Our bodies also cannot be herbivores without processing our food (grasses, grains, many roots).
Are humans omnivores?
We're all omnivores in that we CAN eat meat or egg or dairy should we need to, but we don't NEED to eat them. We are not carnivores - note that we do NOT have canine teeth like carnivorous animals nor do we have the strong stomach acids that they possess. I have worked at a monkey sanctuary in Africa, we fed the monkeys a diet of fruit and vegetables. In the wild, they can eat small animals or insects should they need to, but they live healthily and happily on a completely plant-based diet. Just like humans.