You have probably been told your whole life that humans are omnivores. But some people say we are frugivores which is an herbivore subclass. What do these terms actually mean? And what would be most logical for them to mean?
Some people think diet class terms mean what a species tends to eat, while others think it should mean what the optimal diet is for that animal, and therefore should be what they eat.
If we define it the first way, it should be defined simply by what that species tends to eat, and nothing more. But if we use the second definition, then it should be by anatomy. What kind of proteins is this animal's digestive system is meant to handle? What kind of vitamins do they need and how much? What their teeth look like? And other anatomy facts.
1. It doesn't allow individual animals to change their diet class simply by choosing what to eat. Some animals, like Humans, Deer, and Rats, completely ignore what their biology suggests their diet should be, and will eat anything if given the opportunity. This effectively changes their diet class if we use the first definition.
2. In arguments against veganism, people use the term "omnivore" like it should be used to mean we are ment to eat meat. Despite the fact that our anatomy does not resemble any omnivore, and is almost identical to a frugivore, a lot of non-vegans say we are omnivores. They say this despite the fact that we get heart disease from animal product consumption, and that plant only diets have shown to be the optimal diet for us by a variety of prestigious medical studies
3. Other animals are already described based on their optimal diet. Everyone will agree that cats are carnivores and that cows are herbivores (specifically ruminants). But most cattle in intensive livestock operations have fish and chicken meal mixed into their feed. In fact, cows are among the top consumers of fish. So by the logic of the "tends to eat" definition, cows are actually ocean predators. You see, it is creating a big inconsistency. Just because you eat it, doesn't mean its your natural diet. Eating like an omnivore doesn't mean you're an omnivore. Feel free to express your opinion(s) in the comment section as long as you do it in a civil and mature way.
Diet anatomy chart
Link to studies regarding diet
https://docs.google.com/document/d/1fVAXtjoDYJzSyd99npHaLu2Ylfou3QT07X5lN3JeN0U/edit?usp=drivesdk