When It Comes To The Morality Of Meat, Nature Is No Guide
In her book "Defending Beef," Nicolette Hahn Niman absolves the act of eating meat from moral inquiry on the grounds that humans have always eaten animals. She explains that a "food web" in which animals and plants routinely consume each other (yes, plants eat animals) places all life in "an endless cycle of regeneration." As a result, she concludes: "something so fundamental to the functioning of nature cannot be regarded as morally problematic." Please re-read that quote to make sure it sinks in.
This logic is sloppy, commonplace, and dangerous. Critics of vegetarianism or veganism routinely chant the mantra that humans "were meant to eat animals." This comment has a "no further questions asked" tone to it. It seems intuitively true and, unfortunately, for consumers otherwise inclined to question the moral implications of eating animals, it serves as a convenient escape hatch from a question many meat eaters are eager to avoid: is it wrong to slaughter a sentient animal for food when it's unnecessary to do so?
By relying on the "humans were meant to eat meat" logic, Niman fails to examine the assumption upon which it rests. At its foundation, the claim implies that any adaptive quality that humans might have evolved to survive is, to quote Niman, "so fundamental to the functioning of nature" that it "cannot be regarded as morally problematic."
The problem here is that evolutionary adaptation - the essence of the "functioning of nature"- includes untold morally disgusting behaviors that, while perfectly natural in the same way that eating animals is considered natural, are rightly deemed abhorrent by decent people living in a civil society.
Take infanticide. The adaptive advantage of infanticide for many vertebrates is well-supported. This is true for humans as well as primates. Among the !Kung hunter gatherers of Kalahari, about one in a hundred births end in infanticide. In regions of New Guinea, according to anthropologist Sarah Hrdy, infanticide is "off the charts," as mothers who wanted sons (or whose partners wanted sons) will often kill their daughters.
Rather than accept this behavior as beyond moral scrutiny due to its proven "natural" or adaptive quality, civil society rightly rejects infanticide as a totally barbaric practice. The human corrective, according to many evolutionary biologists, has been monogamy - a civilized arrangement often deemed "unnatural," but certainly morally superior to the alternative.
Another (admittedly more controversial) example to consider is rape. In 2000, Randy Thornhill and Craig T. Palmer argued in "A Natural History of Rape" that the urge to rape is the legacy of an evolutionary adaptive trait (or the by-product of an adaptive trait, such as aggression in men). Their theory (not surprisingly) encountered a firestorm of objection, much of it concerned that evolutionary psychology was being used as "excuse" for inexcusably horrific behavior.