» Sun Jun 03, 2012 4:04 pm
Most alpha-predators have an instinctive taboo against eating other predators. Even when such a predator kills another to defend territory, they leave it to the scavengers. A lion will kill a cheetah, for example, but will not eat it. This is because alpha predators build up non-water-soluble toxins at a higher rate than things lower on the food chain. A deer, for example, takes in all the toxins from the plants it eats, and those that it can't remove build up in its cells. If a mountain lion kills and eats that deer, it takes up all the toxins that the deer was unable to eliminate over the entire course of it's life in a single meal. Scavengers are better equipped to deal with these toxins, because that's their niche, but predators do not eat other predators, in general.
Predators who do eat other predators regularly are uniquely adapted to do so, and these usually only happens in fairly harsh climates. Polar Bears, for example, feed largely on seals, who feed largely on fish. Polar Bears livers are remarkably good at storing these toxins, as a result. This is why, if you are in the arctic and kill a Polar Bear do not eat it's liver. It will kill you.
Humans are strong generalists: we can be nearly pure carnivores (see: Inuit) but humans have not been alpha predators for very long, on an evolutionary scale: there's evidence Homo Sapiens was a prey species for a not-insignificant portion of our time on this planet, and our emergence as the global alpha-predator is recent, occurring sometime in the last 50,000 years. Our ability to evolve into the role is limited, and we still have something of a generalist's instincts.
This kind of went on longer than I had intended, but long story short: people are alpha predators (even if our instincts haven't quite caught up with that yet) and an alpha predator shouldn't eat an alpha predator, because they risk a lethal buildup of toxins. This is also why people shouldn't eat dogs or cats, by the way.