Degeneration and Hybridism in the Early Modern Species Debate: Towards the Philosophical Roots of the Creation-Evolution Controversy

Justin E. H. Smith (Concordia University, Montréal)

Abstract
Early modern nominalism partially maps on to what is today often referred to as “species anti-realism” in the philosophy of biology. According to this latter doctrine, because what we think of as species are but snapshots in time of various, ever-evolving lines of descent, there can be no justification for treating them as real natural kinds. Anti-realism is strongly motivated by evolutionary theory (though, to be sure, many evolutionists remain realists), which takes animal species out of the class of relatively stable, fixed entities, like the elements on the periodic table, and historicizes them, placing them more on a par with, say, nation-states or car models.
     In the 17th century the possibility of change in a species over time was generally associated with change for the worse, and thus was closely connected in the minds of some with the threat of moral decline. It should not be surprising to find that the figures most committed to the fixity of species are also those most committed to traditional theology. Thus the pious John Ray insists unequivocally that “the number of true species in nature is fixed and limited and, as we may reasonably believe, constant and unchangeable from the first creation to the present day.” The perception of the fluidity of species, in contrast, may in large measure be associated with those authors most intent on promoting new empirical methods of natural-scientific investigation that would be entirely independent of ancient authority, whether that of pagan philosophy or of revealed scripture. Thus in the Novum Organon, Francis Bacon notes that there are natural beings “which appear to be composed of two species, or to be the rudiments between one and the other.” He offers as examples of these “Moss, which is something between putrescence and a plant,” and “Flying Fishes, between fishes and birds,” and, finally, “Bats, between birds and quadrupeds.” He goes on to suggest that sometimes these transitional individuals may emerge by way of degeneration: “plants,” he writes, “sometimes degenerate to the point of changing into other plants.”
      Following in Bacon’s path, Locke speaks in the Essay Concerning Human Understanding of creatures that “have shapes like ours, but are hairy, and want Language, and Reason… If it be asked,” Locke reasons, “whether these be all Men, or no, all of humane Species; ‘tis plain, the Question refers only to the nominal Essence: For those of them to whom the definition of the Word Man, or the complex Idea signified by that Name, agrees are Men, and the other not. But if the Enquiry be made concerning the supposed real Essence; and whether the internal Constitution and Forme of these several Creatures be specifically different, it is wholly impossible for us to answer.”
      Locke believes that important empirical evidence in favor of his nominalism comes from what he takes to be the common natural phenomenon of cross-species reproduction. “I once saw a Creature,” he maintains,

that was the Issue of a Cat and a Rat, and had the plain Marks of both about it; wherein Nature appear’d to have followed the Pattern of neither sort alone, but to have jumbled them both together. To which, he that shall add the monstrous Productions, that are so frequently to be met with in Nature, will find it hard, even in the race of Animals to determine by the Pedigree of what Species every Animal’s issue is; and be at a loss about the real Essence, which he thinks certainly conveyed by Generation, and has alone a right to the specifick name.

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