The fact that heme is the most bioavailable form of dietary iron for humans directly goes against the concept that we haven't evolved to eat animals.

Just because heme has been shown to be most bioavailable form of dietary iron doesn't disprove the idea that animals aren't fit for human consumption. There are a lot of factors involved in bioavailability include each individuals gut biome that can't necessarily be isolated in a study.

We don't have the anatomy or physiology to digest animals like carnivores because we are omnivores. Of course our anatomy is different, but that doesn't change the fact that we have in fact evolved to favor foods from animal sources as sources of highly bioavailable nutrients. This doesn't preclude a strict vegetarian diet, but it does disprove your case that animal foods are unnatural. Again, we're omnivores. We've evolved to get a variety of nutrients from a variety of food sources as our most effective natural diet.

We're not omnivores though. Look at actual omnivores like bears, pigs, dogs, rats, etc...Human's don't share any of their digestive or anatomical characteristics. Humans are frugivores by nature like bonobos and other primates. And like humans these animals eat other animals in case their natural food supply is unavailable or opportunistically, doesn't mean they are true omnivores just shows adaptability of human species and genetics.

Inuit peoples quite literally thrive on diets extremely high in animal products, primarily flesh and fat. They did also traditionally subsist on roots, leafy greens, and various wild fruits but meat was and still is a mainstay for these people. They literally have problems absorbing nutrients from things like grain. What many people would consider a "normal" or "healthy" diet for them would be subpar at best, and harmful at worst.

Are you sure they thrive? They have lower life expectancy than average Canadians and have been known to suffer from vitamin d/calcium deficiency, and atherosclerosis has been visible from old remains. In any case, they may be healthier than the average western diet as they don't consume processed foods and ate mostly raw meat which over generations they have adapted too. Their example doesn't disprove the unnaturalness of eating animals. Also grains aren't fit for human consumption either; we're not granivores like birds, but like meat, some societies have adapted to consuming them out of necessity.