Bill Rankin, 2011
This chart began with a simple question: is there any relationship between the evolutionary sophistication of an organism and the ethics of eating it? Digging into the details, I found no easy answers, either to the ethics of food or the idea of "evolutionary sophistication." The best ethical strategy, it seems, is to evaluate each animal on a case-by-case basis.
That said, I did uncover one useful rule of thumb. For land animals, the bigger the better; for water animals, the smaller the better. On land, it's very difficult to keep large animals in cages, while almost all birds and small mammals spend their entire lives confined. (Even "game birds" like pheasants are raised in cages before being released on hunting farms.) In water, smaller organisms lower on the food chain tend to bounce back much better from temporary overfishing, and they don't accumulate toxins like mercury the way that large fish do.