QUESTIONS FROM THE GALLERY

About three weeks ago, in response to my rather animated public denunciation of a presentation of Don Patton, some folk who attended Patton's presentations at Bullard High School expressed some interest in learning what the textbooks actually teach where evolution and natural selection are concerned. I promised to answer questions about the text and my curriculum, so you can expect to see many of these posts over the next week or so.

A correspondent, referencing a paper of mine*, writes:

“In the paper you state the general definition of evolution to be "change over time". This sounds to me like any form that changes/mutates (not sure if I'm using the right terms) to another similar form of equal complexity (micro-evolution), i.e., Darwin's finches, as reported by Peter and Rosemary Grant, qualifies under the general definition of evolution. Is there a different definition for the situation where one form, the coelocanth, mutates/changes into a land animal (macro-evolution)? Or is this still under the general definition of evolution?”

There are at least three potential pitfalls here, and none of them are religious in origin.

PITFALL #1: WHAT EVOLVES?

First of all, it is not an individual’s form that changes, as the brief ‘the coelocanth...changes into a land animal” would suggest. Rather, it is the frequency of alleles within a population that changes. Individuals don’t evolve; populations do, and it is truly amazing how many educated people routinely confuse changes in an individual’s form during its life (development) with changes in a population’s genetic makeup (evolution).

This is a prevalent misconception that works much mischief. For example, in the rather disappointingly-staged Ivan Reitman ‘comedy’ Evolution (it’s not all that funny, either), a whole batch of organisms changes right before our eyes, supposedly morphing in the span of a few hours from simple to complex life forms.



Similarly, as part of the Pokemon craze that peaked a few years back, a character such as ‘Pikachu’ is said to ‘evolve’ into ‘Raichu’—and pretty much instantly! The popular culture, in other words, routinely confuses evolution with metamorphosis, an amazing distortion when you think about it, but one that it is routinely accepted by both proponents and detractors of evolution alike. It’s difficult for me to overstate how much harm is done by this trope. It would be like a physics teacher having to explain, on a daily basis, that gravity is not magnetism, and it could only prosper if there was widespread ignorance about one or the other.


PITFALL #2: DOES EVOLUTION IMPLY COMPLEXITY?

“This sounds to me like any form that changes/mutates (not sure if I'm using the right terms) to another similar form of equal complexity (micro-evolution)...”

The notion of complexity is almost always misleading when considering individual cases of evolution. In the first place, what measure of complexity would you use? In the second place, regardless of which metric chosen, there is no reason to assume that evolution necessarily promotes any particular outcome where complexity is concerned.

True, populations may acquire adaptations rendering their members more fit in a given environment, but does that make the population as a whole more complex than the ancestral population from which it sprang? By no means. The ancestral population might’ve been exquisitely well-adapted to its past environment, much more so than the newly tinkered-with daughter population which is but recently responding to environmental change. In and of itself, evolution does not imply complexity.
In fact, in and of itself, evolution does not even imply speciation (the production of new species)! Evolution is best thought of as a tree with many nodes, rather than a 'ladder of progress' leading ever-upward.

The truth is that biologists don't use the terms ‘micro-evolution’ and ‘macro-evolution’ all that much, and when we do, we don’t use them in the way that the professional creationists do. The latter typically use ‘micro-evolution’ to describe the undeniable genetic changes that occur within populations, but ‘macro-evolution’ to refer to speciation events, which they seem eager to deny.

Now, this leads to an entire can of worms which is in fact religiously motivated, so I will save discussion of the alleged ‘micro/macro’ distinction for another time, but the key point is that, being undirected, evolution itself can not be said to promote complexity, nor necessarily to be in any way progressive.

PITFALL #3: IS THERE A ‘BAIT-AND-SWITCH’?

Is there a different definition for the situation where one form, the coelocanth, mutates/changes into a land animal (macro-evolution)? Or is this still under the general definition of evolution?”

A minor quibble: coelocanths and other crossoptygerian fish are not believed to be ancestral to land animals. But, yes, whether we are talking about changes that occur in a single generation or changes that accrue over many generations, we are still talking about a ‘change over time’ in a population of organisms. Unlike the people in Darwin’s day, we now know that what changes is the frequency of alleles in a population, and so the more precise genetic definition of evolution is still in play, as well.

But, at this point, an unbiased observer might not only wonder when one definition might be preferred over another, they would also wonder if there might be times when one definition is intended, and the other inferred? Or, even more sinisterly, if there might be times where evidence for one definition is misrepresented as evidence for the other—a ‘bait-and-switch’?

Many creationists are convinced that the latter is the case, because there is direct experimental evidence for the latter in contemporary populations, but none (for obvious reasons) from populations past. These creationists often adopt the pose of scientific purist, as if they have discovered some horrible methodological flaw in evolutionary biology, as if (gasp!) drawing inferences was inherently unscientific. They would have you believe that ‘microevolution’ (which they accept) is an example of proven‘operational science’ whereas ‘macroevolution’ is unproven ‘origins science.’

Again, we can discuss the particulars of that distinction at a later date. The point I just want to address is that some creationists imply that biologists are either playing a ‘shell game’ with the word ‘evolution’ in order to deceive the faithful, or that evolutionary biologists are inattentive to important distinctions where that word is concerned. In other words, we’re either lying or blind, which is not a terribly helpful stance.

For my part, I am sure that much of the problem here lies not with the science, but with how the science is presented in the popular culture. My curriculum tries to address that by being very intentional. The first definition is used when presenting the historical context in which Darwin first developed his theory, and when I give it I tell students they will eventually be responsible for a second definition which was developed in part to test the original theory. Later on, when I give the second definition, I remind students of the earlier definition and point out that what makes a theory scientific is that it can be modified or rejected in the light of new data, and that includes how words are defined.

That’s not ‘bait-and-switch.’ That’s the way science works. After all, Aristotle thought there were two forces in the universe: ‘gravity’ (the tendency of heavy objects to fall) and ‘levity’ (the tendency of light objects to rise). No contemporary physicist would be accused of ‘bait-and-switch’ just because they didn’t use Aristotle’s definition of gravity.

* I'm going to put this paper on the Net as a PDF file later this week.

UPDATE: The paper, "Show Me A Walking Fish and We'll Talk", is now available as a PDF file here. However, I should note that there is a misleading passage at the end that implies that crossoptygerian fish like coelocanths are ancestral to modern tetrapods. This is probably not the case! Rather, coelocanths and other creatures show transitional features such as choane which are believed to be derived from a common ancestor to other transitional forms, such as Tiktaalik.