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Is Evolution Widely Misunderstood?

The consequence of adaptationism is that every single trait is an adaptation to something. This is, quite simply, wrong.
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Answer by Marc Srour, Invertebrate palaeontologist, arthropod systematist, historian of biology, blogger at:

Yes. We are all responsible for this.

There are two related issues that lead to people questioning "Why did not species X evolve the trait Y in response to the environment Z?"

Number one is a lack of tree-thinking. We have various ways of diagramming the evolution of taxa, but all of them are some sort of tree diagram, with a trunk and the species branching off it, as branches and leaves. This is, in most cases, the most efficient visualization technique, hence why it's stayed throughout the ages.

But efficient as it is, many people simply do not know how to read it properly. Take a look at the two trees below.

Go on the street and ask people to tell you whether Tree A or Tree B is more accurate, or whether both trees are correct. 99% of them will tell you Tree A. Go to a college campus, even to the biology students, and still most will answer A.

The correct answer is that both of them are exactly the same. Reading a phylogenetic tree is an exercise in counting nodes from the last common ancestor. Most people will answer A because the human is on the right and at the top and therefore appears to be the most derived and "special."

How does this relate to the problems you bring up in the question? It reveals the crucial misunderstandings about evolution. People would not say Tree A is the correct one if they didn't think evolution has a direction that leads to the favourability of the human phenotype or of human intelligence.

And this leads on to the other problem: adaptationism. Adaptationism is a now-debunked idea that natural selection is an all-powerful force that leads to the evolution of everything. Since Gould & Lewontin comprehensively debunked it in 1979, it hasn't been taken seriously in most evolutionary circles, although there are bands of biologists who still insist on overemphasizing natural selection.

The consequence of adaptationism is that every single trait is an adaptation to something. This is, quite simply, wrong. A trait can be a side-effect of a true adaptation. A trait can be the result of genetic drift or of natural variation, and not naturally selected for. I have written on the issue of adaptationism here, if you want to read more: Adaptive traits, adaptations, and adaptationisms.

Adaptationists come up with "just-so stories" to explain the evolution of any trait as advantageous. These stories are intuitively appealing, very simplistic, and thus are easy to memorize and spread.

All of the questions of the type that you lament, the "Why did not species X evolve the trait Y in response to the environment Z?" questions, are yearnings for adaptationist just-so stories. They just want a simple explanation that sounds good, even if it falls apart once you start examining it. Most often, these explanations also appeal to preconceived notions. But most will not examine it, because the lack of tree thinking makes them incapable of properly interpreting the evolution of any trait. For the easiest example: read any popular evo psych. 95% of that is adaptationist junk, unevidenced and quite nonsensical. But it's also extremely popular, because it reinforces current societal gender and sexual norms, so not many try to read further into it and criticize it properly (which really, really isn't so hard to do).

Who is responsible for this state of affairs? As I said at the beginning, we all are. Starting from us scientists, who quite often blurt out adaptationist explanations because their simplicity means we can answer questions quickly. Most of us don't mean to do it consciously, but that's not an excuse. I personally slap myself whenever I inadvertently do it and rush to correct my mistake.

Then we have science popularization efforts. When it comes to evolution, it's a sad fact that you will still see, more often than not, evolution portrayed linearly, or as showing some sort of trend. On the one hand, it's understandable since things need to be kept less complex, but it's also severely misleading, encouraging both adaptationist thinking and discouraging proper tree-thinking. School curricula also do a horrible job of introducing students to these things.

And finally, we have the general populace. They are mostly victims of the inept evolutionary biology curricula in schools, admittedly. But there are also firmly-held ideologies and beliefs that disrupt proper internalization of evolutionary principles. Religious views are the most common. I know many people, religious, spiritual, atheist, who have no problem with evolution ... but as soon as I show them Tree B, they refuse to listen anymore because of a perceived slight on the uniqueness or extravagance of humans. This is a remnant of the old Scala Naturae that dominated the Zeitgeist for millenia, and it's still very common. It's a cultural manifestation of the lack of tree-thinking, in that we are culturally primed to consider that there is an end goal to everything, and that that end goal in the case of evolution is the all-amazing Homo sapiens, conqueror of Earth and the Universe, rather than the correct evolutionary view that humans are just one leaf left in an enormous tree, with nothing really remarkable about us.

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