Many years ago, when comparing, and seeing others compare, the birds from the separate islands of the Galapagos Archipelago, both one with another, and with those from the American mainland, I was much struck how entirely vague and arbitrary is the distinction between species and varieties. On the islets of the little Madeira group there are many insects which are characterized as varieties in Mr Wollaston's admirable work, but which it cannot be doubted would be ranked as distinct species by many entomologists. Even Ireland has a few animals, now generally regarded as varieties, but which have been ranked as species by some zoologists.Richard Leakey, who wrote the introduction and edited the abridgment of the edition of the Origin I've been reading lately, says:
[Darwin's] opponents believed that each species had been separately created by God, but that varieties had arisen within these species by natural variation.This would be a reasonable distinction from the creationist point of view today as well, if there were any way to know which was which with any certainty, but even now when we have the science of genetics it isn't always possible to know. In Darwin's day it was entirely a matter of the degree of difference in appearance from other groups as subjectively judged. When a new distinct group was known to have descended from another it was called a variety, but in most cases this was not known for wild species, so naturalists determined which was which according to the degree of difference they thought they could identify from observation.
It's tempting to quote Darwin at great length where he describes the species-variety confusions of his day because it's really quite fascinating to see how they thought about these things in those days, but Darwin's main intention in spelling it all out was to lay the groundwork for his theory of how a species can evolve into another species, as Leakey says:
Hence Darwin's overriding objective is to minimze the distinction between species and varietiesWhere to draw the line between species and varieties is still the problem for creationists, though no longer for evolutionists, who have found an objective way of defining a species -- not necessarily true of course, but objective at least. As Leakey puts it: (62)
Modern biologists would define a species as a group of individuals all of which can potentially interbreed one with another. This is a working definition which holds good in the majority of cases. There are anomalies however, some of which Darwin deals with ...So evolutionists have a definition of species that sounds fairly definite and objective although of course they maintain that a species can eventually change to the point of producing another species. But at least since a species in Darwin's time was subjectively determined by judgment from the appearance of the creature, meaning there was no way to establish it as fact, so now there seems to be a criterion that works and at least puts a stop to the subjective uncertainties.
But now creationists have been deprived of the very term species. It has now been defined to support the theory of evolution, assuming endless ability to change from one species to another, where it used to imply the immutability attached to special creation. Consequently, creationists have had to scramble to find a different term to refer to the Biblical created kinds, sometimes resorting to "type" or "group," and sometimes using that very Biblical term, kind. The problem is that all the relevant terms are more or less interchangeable. Species simply means "kind" or "class" or "type."
But the earlier creationists had already stretched the concept of the Biblical created kinds to such an extent that it had lost all meaning anyway. Creationist naturalists had no problem splitting many of what today would be considered to be immutable separate Species -- such as Cats or Dogs or even possibly Birds -- into several species rather than varieties, considering them to be special creations in their own right, judging subjectively by the appearance of their differences. Creationists in those days could very easily have accepted Darwin's many "species" of finches for instance, regarding them as separate creations. (And this way of artificially multiplying species, which evolutionists continue to do today, is the reason for the challenge by evolutionists that there would have been far too many species ever to have fit on the ark. But if most of what are now called species are really just varieties of an original Kind, room on the ark for the species of that ancient time is not a problem).
But these days the evolutionist redefinition of species now precludes this kind of classification for creationists. And that's a good thing. This is one of the effects of Darwin's work for which I think we should thank him. It seems to me easy to sympathize with Darwin's objection to the arbitrariness of the subjective distinctions of his day. There was clearly a need for a more objective system to distinguish a species from a variety, and not only biology in general but also creationism could only stagnate under the imprecise subjectivity of classification he criticized.
Of course creationists must object to the evolutionist definition, but thanks to that definition we are now forced back to the Biblical perspective. The unbiblical idea of separate creations after the original creation described in Genesis had to be abandoned, the readiness to assume that striking differences between groups make them species as opposed to varieties had to go, the glib explaining-away of odd phenomena as simply having been created for some purpose had to give way to an empirical way of thinking about those things.