For my final essay I had to write for my biology minor from my undergraduate degree, I wrote about human teeth and how they've evolved over time. I presented to my teacher with the hypothesis/thesis that humans could easily go "full herbivore" or "full carnivore", depending on the enviornmental pressures that happens over the next few hundreds of years.
If we were "never meant to eat XYZ" (animal or plant matter here), our digestive system wouldn't have evolved like it did. Our GI tract is rather unique in this regard with just the sheer variety of what humans can digest and actually gain nutritional value from.
Humans are extremely unique in the biological sphere we call Earth, in both biology and ecology (the science of how all organisms interact with each other, including predator-prey relationship). Despite the fickleness of food science, there have been some interesting finds regarding it (for example: it takes the human body a lot longer to process plant-based proteins as opposed to animal-based protein due to the biochemical makeup of said proteins).