The instinct to eat animal protein

The hungry doe that I met at the campground certainly had no idea about any of this evolution business. She didn’t know about differing levels of protein, iron, or salt. She smelled a steak cooking, she wanted to eat it, and it wound up in her mouth. Come to think of it, this was pretty much the same reason why I started eating meat after growing up as a vegetarian.
--Jackson Landers, When herbivores attack! Plant-eaters' secret meat snacks, Slate.com

Somewhat of a sensational title for an article, but a moderately-referenced article that summarizes several known case reports in one-liners for busy readers interested in evolutionary explanations for nutritional niches as well as breaches.  Like Jackson Landers confesses, I too was raised vegetarian but started eating meat early in life, despite the guilt, the fear, and the confusions, because, as the adult in me rationalizes, my body, more so than the principled adults responsible for my welfare, knew when it needed the protein it lacked.  Divya, my 8-year old vegetarian-leaning daughter, goes through periodic cycles of requests for ham sandwiches, chicken curries, fried eggs, or tuna salads, unprompted by the more omnivorous members of the family.  Legacy (the dog), whom some might consider the most carnivorous member of the family, chomps on grass every 3rd day, and especially when given boiled meats and a bone to gnaw on.  These are but anecdotal suggestions from my family's experience that nature can hardly afford to be rigid, as survival is such a flimsy exercise with no guarantees on outcomes as well as the means to those outcomes.

But most vegetarians I meet, like the doe that Landers met, are not rationalizing their decisions and choices in evolutionary terms.  They invoke ethics, morality, religion, animal rights (or lack thereof), culture, reluctance to kill, disgust about killing, sense of right (vs. wrong) and several more socially constructed arguments including social politics and agricultural economics. While each of these stances interest and engage the comfortable, grateful, and balanced omnivore in me, I am quite appalled when people bring no curiosity, knowledge or questions about the role of biology or evolution to the discussion table. In certain circles, judgements about the meat-eating habits of other human beings, even whole societies, based on uninformed opinions are quite the norm. And opposition to meat-eating, either in the form of gentle persuasion or outright disapproval, is on the rise.

It seems like the title of Landers' article has been changed to something more mild and appropriate such as 'Bambi ate Thumper: Why herbivores sometimes eat meat.'