Do we require animal food? No. I choose not to debate whether we are frugivore or omnivore, if our intestines are too long for meat or we are physiologically meant to be vegan or not. That aside, we do not require any animal food to thrive and survive.
Since there is another way, I prefer to live that way. Aside from personal preference, a society with less dependence on animal foods also saves water wasted from watering crops for animals for slaughter, reduces gases that the unnaturally large number of animals release, eliminates or reduces the poor treatment of them, and then there's the subject of health and nutrition.
Some people find themselves in a health crisis where a vegan diet can save their life but nearly never have I seen a case where an animal food diet would offer the same life saving changes in one's body. Not even in treatment for cancer when blood building might be needed; I have helped raise a clients' blood count in two weeks using a vegan method over the animal alternative of blood-rich beef liver and meat. That life-giving quality in living foods paints a big picture as to the value of plant-based, whole foods.
Now, there is no 'across the board' rule for everyone and there are sometimes cases where meat or animal food may be better than none, such as: instances of malnutrition, lack of other caloric intake, wild caught occasional consumption, seasonal lack of nutrients, etc. However, for people with access to a variety of fresh vegetables, fruits, legumes, beans and grains, there is no 'need' for maintaining the extremely disproportionate dependence on animal-based food.
For those who do eat animal food, there are always better choices amongst the types, treatments and cooking methods. Wild caught, free range, anti-biotic free, hormone-free, non-gmo fed, non-grain fed, organic choices are best when selecting meat, eggs or dairy. Raw dairy is more digestible if available and bison is a better choice than beef. Of all the animal foods available, the ones with the most nutritional benefits include cold water fish such as salmon and halibut, eggs and wild turkey.
For more information on how to eat vegetarian, attend my 'Vegetarian Nutrition for Beginners' class. Check calendar for dates and details.