Consequences and (Evolutionary) Intentions

Perhaps one source of confusion in discussing evolution is that people do not clearly distinguish between “consequences” and “intentions.”  While modified or new traits may have the consequence of enhancing reproductive survival, that does not mean that they arose with the intention of enhancing survival.

Consequence is a term of cause and effect analysis; intention is a term applicable to the actions of thinking and willing beings.

The confusion arises (and/or is expressed) when people use expressions indicating intention, often in metaphorical ways yet not recognizing that they are metaphors.  Expressions such as “in order to” seem innocent enough, but they imply directed intention.  For example, to say that the peacock’s tail evolved in order to attract peahens implies that a series of changes to the tail of peacocks had a goal and was not simply a consequence of those changes.

This, of course, raises the question of when natural selection actually comes into play.  Certainly the initial change arose by “accident,” but at some point it will in some way confer some kind of advantage on its bearers—females being more attracted to a slightly bigger or more colorful tail than to a plain one—in order for it to become characteristic of a species, rather than a rarity.  But obviously bigger tails are not intrinsically attractive, as most species of birds do not have such big tails—some gain the same effect through crests, or wattles, or wing displays, or songs, etc., so obviously some sort of change must also occur in the females that leads them to respond to the specific trait of big colorful tails (females of other species are not attracted to the peacock’s tail).  (Along the way, there must also be the factor of recognizing males of one’s own species and differentiating them from males of other species—a female chicken who was attracted to a peacock’s tail would, of course, not successfully reproduce.)  Each increase in elaboration of the male’s tail would arise accidentally and then survive only if it elicited the appropriate response in females (not to mention other limitations, such as a tail too big interfering with the male’s ability to escape from predators).  Thus, there are many factors that cannot be attributed to intentions, however defined.

Why, then, if modifications do not arise from intentions, which would at least have the advantage of offering a logical explanation for these modifications, do they seem so purposeful?  How can something as clearly purposeful, or at least as functional, as the peacock’s tail or the human hand, not have been intended in some way?

First, the problem of hindsight:  we observe how the tail or the hand suits their functions, and therefore conclude that they originated with such a function as their final cause or intention, their goal.  But there is no intrinsic reason why we must make this assumption, except that it is the habit of centuries to find design in function.  But as has been observed many times, the bones that constitute the human fingers are, in other creatures, the framework for wings (bats), claws (dogs and cats), hooves (horses, down to one “finger” now); thus, these bones had many directions in which they could evolve, and interestingly, they did so.  We should also note that the uses humans make of their hands are consequent to the development of them; we discovered that we could not only grasp things with our hands, but could use them to carve stone and wood into sculptures, write letters, play musical instruments, and so forth.  It is impossible to believe that Nature or Evolution intended these uses—we had hands and subsequently found a wide variety of uses for them.  While considerably less the case with other animals, it is nevertheless as likely that they developed a feature and then found uses for them.  One of my cats, for example, uses her front paw to drink water, by dipping her pads into the dish and then licking the moisture from the pads; she will not drink with her mouth directly from the dish, as my other cats routinely do.  Obviously, animals learn how to use their various body parts.

The other point is that once a new trait begins its development, it tends to continue along that path, in what has been called path dependence.  For example, once the primate line started down the path of development that led to the human hand, it was not likely to detour into the development of bat-like wings; and likewise, it is not likely that bats would now detour into developing human-like hands or cat-like paws.  It would appear that the logic of evolution runs like this, and not according to intentions or final causes.  Indeed, it may only be by giving up the idea of evolutionary teleology that we can account for the nearly infinite variety of living organisms—no intellect could devise so many variants of variants as the natural world contains.  No intellect would want to.


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