Mutants, Apes, and Evolution — Oh, My!

I went to see the new X-Men movie this past weekend and saw this intriguing trailer:

I was excited — this looked like a good movie! — right up until I saw the word “evolution.” Since I was there to see a movie about human mutants with superpowers, I couldn’t justify getting too upset about abuses of evolution. But it was precisely seeing this trailer and that movie in the same night that made think about how media reflect popular misunderstandings of evolution.

Darwinian evolution by natural selection seems like a simple idea. Individuals within a population are all a little different from one another. Some individuals’ features enable them to survive and reproduce better than others. Their offspring will resemble them and repeat this process. Over time, these differences in survival and reproduction lead to changes in the frequencies of different traits. When populations become separated and no longer interbreed, new species emerge.

Easy enough, right? Yet, many people — even people with years of biology education — grossly misunderstand this theory because it violates our intuitions.

Michel Ferrari and Michelene T. H. Chi (1998) argue that incorrect understandings of evolution are driven by miscategorization. Evolution is a process, but many people think of it as being more like an event (for example, a baseball game) than like an equilibration process (for example, sugar disolving in water).

An event, like a baseball game, has a clear beginning (the first pitch) and a clear end (the final out). It has distinct actions that occur in a specific order (first, a pitch is thrown; then, the batter swings at the ball). These actions have causal or contingent relationships (the batter goes back to dugout only when he is “out”) and are directed at a goal (winning).

Equilibration processes are basically the opposite of events. They have none of these features. Think about sugar dissolving in a glass of water. The molecules of water and sugar move around randomly, without any goal. They don’t start or stop moving based on the concentration of the sugar in the water, and they will move regardless of what all the other molecules are moving. That the sugar eventually becomes evenly distributed throughout the water is just an emergent result of all this random movement. The get a visual of how this works, watch the beginning of this video:

Evolution is more like sugar dissolving in a glass of water than it is like a baseball game. It doesn’t start when one feature “begins” to change within a population or stop when new species branch off. Changes within a population aren’t directed at the “goal” of surviving, and they don’t have an order or contingency. Instead, many pressures act simultaneously and continuously on the various genes in a population, like the water and sugar molecules move simultaneously and continuously in the glass of water.

If that’s difficult to understand, it might be because I’ve written it poorly. It also might be because it’s just very hard for humans to think about equilibration processes — especially when we are used to thinking about something as an event.

To test their idea, Ferrari and Chi looked at how college students wrote about five different evolutionary problems. They coded all of the responses according to how frequently event- and equilibration-like descriptions were used and whether participants evoked Darwinian or non-Darwinian explanations.

Overwhelmingly, participants gave more event-like descriptions of evolution than equilibration-like descriptions. 62% of the coded items referred to the properties of an event, but only 8% referred to the properties of equilibration. Below are a couple of examples of each type.


“The species must adapt, or it will die out (or become extinct).”

This response alludes to an end-point for evolution: extinction.

“If the tree is to survive in the environment of the field, it will have to develop traits that are conducive to the amount of sunlight, water, parasites, etc. so it can continue to flourish.”

This participant sees survival as a goal and provides an event-like pattern (order and contingency) to evolution.


“Darwin believed that evolution is always occurring. Therefore, the ducks would still be changing now, not simply in the same form which they were thousands of years ago when the change first took place.”

This response explicitly acknowledges that evolution is ongoing and didn’t stop at some arbitrary point when ducks became ducks.

“If one of the trees that was planted in a more parasitic environment had genes that protected it better, it would survive and reproduce while the other trees died.”

This participant describes the simultaneous nature of the evolutionary process. Rather than saying one type of tree turns into another, s/he states that some trees in a population will survive at the same time that others do not.

These might seem like petty distinctions. As long as we understand the basic ideas behind evolution (variation, heritability, differential survival and reproduction, and change over generations), it doesn’t really matter if we think of it as an event or an equilibration process, right?

Using event-like explanations was negatively correlated with Darwinian explanations and positively correlated with non-Darwinian explanations. That is, the more participants thought of evolution as an event, the less likely they were to understand its core ideas. Equilibration thinking, in contrast, was positively correlated with Darwinian explanations. Thus, the more participants thought about evolution as an equilibration process, the better they were able to describe it in terms of its fundamental principles.

So it does seem to matter whether we think of evolution as an event or equilibration process. But what’s left unanswered by these data is if learning the principles aids in thinking of the correct process or if using the correct process aids in learning the principles.

How do X-Men First Class and the Rise of the Planet of the Apes trailer do? Pretty poorly. (For an amusing summary of X-Men‘s failures, check out this column at Scientific American.) Both portray evolution as an event. In the case of X-Men, evolution moves towards the goal of a more advanced “mutant” species, and in Planet of the Apes, the single (Lamarckian) change in intelligence drives forward a “better” chimpanzee species. But good stories have beginnings and endings. They have goals and contingencies. It may be better to put away one’s science goggles and enjoy the fictional worlds than to worry about whether the evolutionary histories of telepaths and super-smart chimps are accurately told.


Ferrari, M. & Chi, M. T. H. (1998). The nature of naive explanations of natural selection. International Journal of Science Education, 20, 1231-1256. DOI: 10.1080/0950069980201005


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