What Is a Species?


That science is a human enterprise and not some pure and perfect object independent of culture is highlighted by a recent investigation into the DNA of American wolves—the gray wolf, the Eastern wolf, and the red wolf. An article in the New York Times (7/27/16) reports that analysis of the DNA of these three wolf species reveals that in fact “there is only one species [of wolf] on the continent: the gray wolf.” The other two are hybrids of coyotes and wolves—Eastern wolves are 50/50, red wolves are 75 percent coyote and 25 percent wolf. The investigators also concluded that the wolf and coyote species shared a common ancestor only 50,000 years ago, which is very recent in evolutionary terms.

Now, anyone comfortable with the fact that nature goes its own way without regard to the human need for tidy intellectual categories is not likely to be much disturbed by these findings. But such people are relatively rare, especially in academic and political circles, so it happens that certain people do find it disturbing that Eastern and red wolves are hybrids. That is, they are not “pure” and therefore may not be entitled to protection from, say, extermination—they are not “pure” and therefore not entitled to the protection of such laws as the Endangered Species Act. In a sense, they are not “natural” because—well, because they violate the notion of the purity of species, they don’t fit neatly into our conceptual categories. As one scientist was quoted (in dissension from the worry warts), “’We put things in categories, but it doesn’t work that way in nature.’”

Indeed it doesn’t. In fact, it couldn’t. The notion of “species” as neatly distinct forms of life, immune to crossings of the so-called “species barrier,” among other common myths of the “logic” of evolution, would cause evolution to grind to a halt. Evolution requires messiness, contingency, happenstance, the unexpected, for it to work. For example, genetic mutations do not magically appear in consequential response to environmental pressures, just in time to save a species from extinction. Instead, a mutation lies quietly in the background, sometimes for many generations, to emerge as the crucial factor of salvation (for those individuals who carry it, and their descendants) when and if a factor in the environment calls it forth.

I am reminded of a startling discovery during the height of the AIDS epidemic in America, that some individuals, despite a particularly risky lifestyle, were immune to the disease. Turns out, they carried a mutation that had first manifested itself centuries earlier, during an epidemic of an entirely different disease, bubonic plague. One could describe how this mutation protects against both diseases, but one could not explain why—why this gene mutation occurred in the first place, why it just happened to confer immunity or resistance to these two quite different diseases (one caused by a bacterium, the other by a retrovirus), and why it resided silently in the genomes of its fortunate carriers for so many generations before it could prove its usefulness.

A fundamental goal of all human endeavors is to reduce the entangled complexities of life, including our own, to a simple set of principles that fit the limitations of the computational power of our little brains, a mere three pounds of meat, of which only a relatively small portion engages in the tasks of reasoning. Not surprisingly, it is difficult to wrap our heads around the genuine complexity of the earth we inhabit, let alone of the cosmos. Being the limited creatures that we are, we need our categories—but let’s not worship them. Let’s not condemn the Eastern wolf and the red wolf to extermination just because they mess up our laws.

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