Monday, March 24, 2014

Are we removing the wisdom along with the teeth?

When I was a kid, I learned that my uncle had a sweet tooth right about the time I discovered that he had a gold tooth. Therefore the gold tooth was the sweet tooth and, man-o-man, did I want a gold tooth... or a whole grill of gold teeth. The better to taste the sweets!

I've grown wiser with age, knowing, of course, that our teeth don't taste sweets (or at least that it's unconventional to think so). And knowing, of course, that "wisdom teeth" don't bestow wisdom, but are nicknamed so because they erupt last, coinciding with the stage in our lives when we're old enough to do adult things, both according to biology and culture.

Whether or not wisdom is actually present or actually required to vote, to smoke, or to make babies is not the point. The point is, like with whole sweet tooth thing, I understand that wisdom teeth don't come with wisdom, but sometimes I do wonder whether this massive, automatic third molar removal system that we've created for everyone in America who's got dental insurance is removing more than just enamel and dentine from our heads.

What if we're also removing a bit of our minds?

Okay. That's just me, losing a bit of my mind, thanks to an enormous pile of papers I've been grading.

But the metaphor's got teeth, given how the assignment I just graded was about... dun dun duuuuunnnn... the oft spun story of our species' future without third molars.

This assignment that I'm grading got me wondering about wisdom loss because the overwhelming majority of students could not do it.  Here it is:

The future of human wisdom teeth
1. Read this blurb  about a very common perception of human evolution. (source)

About 25 to 35 per cent of people will never get their wisdom teeth (RAFFI ANDERIAN)
Wisdom teeth might be lost as people continue to evolve: Why the modern diet may make wisdom teeth unnecessary 
By: Astrid Lange Toronto Star Library, Published on Tue Jun 25 2013 
Wisdom teeth are the third and final set of molars that most people get in their late teens or early 20s. But not everyone does — the American Dental Association estimates that about 25 to 35 per cent of people will never get their wisdom teeth. Another 30 per cent will only get 1 to 3 of them. Anthropologists believe wisdom teeth evolved due to our ancestors’ diet of coarse, rough food — leaves, roots, nuts and meat — which required more chewing power and resulted in excessive wear of the teeth. Since people are no longer ripping apart meat with their teeth and the modern diet is made of softer foods, wisdom teeth have become less useful. In fact, some experts believe we are on an evolutionary track to losing them altogether.
2. On a separate piece of paper…(typed is preferred but not required)
a. Briefly explain the evolutionary mechanism(s) behind the evolutionary scenario for future wisdom tooth loss that the author of the blurb alludes to. In other words, think about what the writer is really hypothesizing for future human evolution and rephrase it, scientifically, in terms of the four main mechanisms of evolution that we discussed in class which are mutation, gene flow, genetic drift, and selection.
b. Write out an alternative scenario where natural selection is responsible for the loss of wisdom teeth in our future selves. If it’s not obvious, this will be an obviously and significantly different scenario from what the writer has imagined in the blurb. Important! Banned words for your scenario include: Need(s/ed/ing), want(s/ed/ing), try(s/ed/ing), best, most.


Only a handful of students performed this assignment correctly.

Despite my hints in 2b, most still wrote 2a using natural selection. Few spoke of mutation let alone drift in their answer to 2a. What's more, many used genetic drift scenarios (without using the term) for 2b!!! If they got anywhere close to the right answer in 2b then they stopped at something like "mutation arises and it proliferates in future generations"... no talk of a benefit to losing teeth or a cost to having them, no talk of adaptation. This is drift and they think it's natural selection. Or they're sloppy writers. Or both.

So what's going on here? Lots. Here's a little bit of my analysis:

First, it's true that I deliberately chose this example, the future wisdom tooth-less humankind, because it is a well-known scenario out there and I knew that unraveling it would be a challenge as a result of its fame. It's a great example of the kind entrenched in the popular zeitgeist about trait loss and future evolution. And so I wanted to take it head on, but I didn't expect such utter and nearly complete failure in this learning environment I tried to cultivate.

Yet again, I'm reminded that stories stick. Not just stories about our future without M3s, but just-so stories like adaptation by natural selection. Selection stories stick so well that students think any and every evolutionary scenario they come across or that they dream up is nothing other than natural selection!

I have to tell them, as I often do, how great they are at genetic drift and how great they already were at genetic drift before entering my classroom. Yet they continue to insist that genetic drift is natural selection.

The textbook certainly doesn't help. I hadn't looked at the definitions in the glossary until a student used one in his answer... Check this out:

"natural selection. Differential reproductive success over multiple generations."

That also defines genetic drift!

A few students admitted to not having any wisdom teeth at all growing in, or to knowing someone who never got theirs (not even crowns in the crypts). So they understand that there's already variation, or that there hypothetically very easily could be. They get the concept of variation because they're surrounded by human variation and they see themselves as unique. They know they're not clones of either of their parents too. 

So why is it so hard (and even "confusing" as I've been told by a student) for them to accept perpetual change via mutation, recombination, and probabilistic inheritance of one or the other allele from each parent. Mutation and drift... these are constantly occurring and have been for millions and billions of years. Natural selection allows this persistent, perpetual change in lineages and populations! What's more, if everything was under natural selection, if everything is evolving only due to natural selection, we'd be so screwed! From my perspective, it doesn't make any scientific sense to be a hyper-adaptationist. To me, it's a creationist's way of thinking.

But what would anyone expect from a student who's been bombarded with natural selection as "*the* mechanism of evolution" (quote from episode 2 of Cosmos with NdGT)? What would anyone expect from a student who's learning evolution at the college level from, either, folks who are suspicious of it for its social abuses (stemming from that very obsession with natural selection!) or from folks who study evolution itself (which means that, if they're successful, if they have papers published at all let alone in the top journals, then they default to natural selection as an explanation for the trait or the phenomenon they're studying, and usually don't ditch their adaptive explanation unless it's replaced by another adaptive one).

What else would I expect from my students? This is what I should have expected. So I can't believe I thought that they'd do better on this assignment after only one lecture on the mechanisms of evolution from me, after only one momentary exposure to genetic drift.

But since then, lucky for them, they've heard about these issues every single day. And maybe someday down the road "arrival of the frequent" will be better understood both within and beyond the classroom as well. Who knows.

Does it count as a good place to start when most fail? It certainly does since the only direction from here is up.

Except there's the fact that many if not most of my students have had their wisdom teeth removed already or have plans to this year or next. I too have had my wisdom teeth removed. So maybe we're a lost cause.

Or maybe not. It's possible that wisdom or at least experience can be an obstacle to learning. With age, we lose plasticity. That whole, you-can't-teach-an-old-dog-new-tricks sentiment is sort of kind of true for people, regardless of whether it's true for dogs. Very young children can be far more cognitively loose, inventively creative than people are later in life. The latest in this comes from Alison Gopnik's research which was reported at Time magazine (with a kind of weird headline). [This might be part of the reason that children are notoriously hard to trick with magic, at least compared to adults.]

And maybe this phenomenon (considered perhaps too broadly here but I can't resist) that our minds become more rigid as we learn, as we grow up, is contributing to the difficulty I have teaching evolution to undergraduates in my introductory biological anthropology course. After all, as the Time article says,
Their previous experience in the world, which tends to work in a single-cause-equals-single-effect way, hampered their ability to accept the unusual rules that activated the toy; they wanted to believe that it was activated either by a single color or by a combination of colors, but not both. “The training didn’t seem to give them a hint that the world might work in different ways,” says Gopnik, who published her work in the journal Cognition.
So what's next? I'll stop fantasizing about lost wisdom and, instead, I'll be assessing whether the students who've had their wisdom teeth removed, or never had them grow in the first place, are learning evolution better than the rest. Obviously. 


Ken Weiss said...

Very fine, Holly. The big problem, to those who actually think about it, is not that chance may drive genetic change, but that organized complex structures can evolve. Darwin didn't really understand chance in modern terms, but he did want to show that gradual, systematic, force-like selection could generate complex structures (like eyes and the ability to write great posts like yours).

Darwin wanted to oppose spontaneous generation or creationism. His simple reductionist answer, brilliant though it was, ignored a lot that we know occurs in evolution. Personally, I think that we do not yet really understand how organized organ structures evolve--though I think selection and chance are both involved. I think that in the future when a better model is found, it will contain elements of these and other things, like complex functions of individual genes and much more (perhaps than any one currently suspects).

But your post also shows important issues about our often comparably simplified ideas about what education is and does. These issues may get deep into human culture and behavior, the need for simple answers perhaps, and so on.

In my view, your students are unusually lucky to have you trying so hard to stimulate understanding and thoughtfulness. How many can be reached is unknown, but some certainly can (and they won't forget it and how it happened and under whose influence).

Holly Dunsworth said...

I'm relishing it all especially today. We've been covering speciation and today, specifically, how species are human inventions, not received knowledge...and that all knowledge is human invention... and it's blowing their minds and I am just a pig in sh!t.

Holly Dunsworth said...

P.S. I look forward to humankind's better understanding of non-selective mechanisms of the evolution of complexity. For the time being, I'm maybe more comfortable than I should be at seeing it all around us!

Ken Weiss said...

Sounds great (well, not about you and the pig and all). I usually show adaptive human differences by comparing people from Tierra del Fuego and South Africa, and noting that these are adaptive differences, at least ~100,000 years old, yet no speciation. And that we know from examples that small genetic changes, having nothing to do with adaptation, can lead to mating incompatibility (I think there is a single nucleotide difference in two groups of Drosophila that has this effect).

There is a natural tendency to be like ostriches, and ignore things we know if they cast doubt on accepted (simplified) explanations.