Thursday, August 27, 2009

Why 'evolution'?

“Evolution” is the label or single-word concept we use in English as shorthand for what we would otherwise describe as the intellectual contribution of Charles Darwin.

But is this term really the best choice?

Etymologically, the term is derived from the Latin evolvere, meaning unrolling, or unfolding. Merriam-Webster’s defines evolution variously as “a process of change in a certain direction”, “the process of working out or developing”, etc.

I think it’s safe to assume that to most people, the term connotes change. I know that’s what I used to think of when I heard the word “evolution”: a living species changing over time to become something new.

And here’s this, from a prominent book on science education standards (Science for All Americans), regarding Darwin’s intellectual contribution:

“…Prior to Darwin’s time, the prevailing view was that species did not change, that since the beginning of time all known species had been exactly as they were in the present….

One line of thought was that organisms would change slightly during their lifetimes in response to environmental conditions, and that those changes could be passed on to their offspring…

Darwin offered a very different mechanism of evolution. He theorized that inherited variations among individuals within a species made some of them more likely than others to survive and have offspring, and that their offspring would inherit those advantages. Over successive generations, advantageous characteristics would crowd out others, under some circumstances, and thereby give rise to new species.”

(Italics mine.)

So again we see: the focus is on change, undoubtedly a result of our use of the term “evolution” to encapsulate Darwin’s main idea.

I propose to challenge this. Isn’t the existence of species-change less fundamental than common descent (i.e. the notion that all organisms are literally blood-relatives of each other, however distant)?

Wouldn’t common descent better capture the profoundest insight of Darwin’s intellectual contribution?


Anonymous said...

I always label Darwin's view as "evolution by natural selection." This not only captures the common descent idea, but also distinguishes his view from Lamarck's evolution by acquired characteristics view.


doug said...

But I don't see how "evolution" or "natural selection" capture the idea of common descent (or common origin). To be sure, all of these concepts are interconnected (species are of common origin; the mechanism of their subsequent separation from each other is natural selection), so I'm not disputing that conceptually it's implied. My beef is with what we choose as the label to package the whole thing. Isn't the notion that all organisms are blood-relatives of each other more fundamental and profound than the fact that they've changed over time (by means of natural selection) to give rise to the diversity that we observe?

The cash value of finding whether I'm right is that I suspect many laypeople, when they think of evolution, think only of some species morphing into something new. I'll bet money that most people have never actually *really* paused on the idea of common descent, i.e. that the tree in your front yard is, in some sense, your cousin.

doug said...

PS: And what's the fetish with the mechanism of action? To me at least, what's revolutionary is so much more than the mechanism: it's the discovery of the very phenomenon itself! In this respect, I feel like Darwin really hit the ball out of the ballpark; had he merely laid out evidence for the principle of common descent, that in itself would have been a homerun. (I hope my sports metaphors are actually correct--homeruns without hitting the ball out of the park are possible, right? GAH!)

doug said...

A couple of people at work have convinced me, I think, that by focusing on "common descent", I'm then not giving due consideration to the aspect of Darwin's thought that re-orients us to consider the importance of individual *differences* between organisms, not just similarities (i.e. relatedness) between organisms.

In other words, Darwin's thought made us aware of both the idea of common descent *and* the idea of individual variation.

Even so, I'm still not satisfied with using the term "evolution" to denote the body of Darwin's thought. I feel like it focuses too much on *change* and therefore *differences*, and not similarities.

Maybe it would be helpful to put it this way: what if laypeople today, instead of referring to Darwinian thought as "the theory of evolution", referred to it as "the theory of common descent"? Would that lead to greater conceptual confusion or clarity? Or perhaps make no difference at all?