Then What Are Toenails For?: Evolution, Neuro-cognitive Diversity and ADHD

The following article has been published with kind permission from Lew Mills, PhD, MFT, a Bay Area psychotherapist who worked with Attention Deficit in Adults.

by Lew Mills, PhD, MFT

As I sit and begin to write, my laptop balances precariously on my knees. If it should slip, it might smash onto my toes. However, my ancestors have evolved a smart little defense for my benefit. My tough toenails protect my toes (though not enough). Is that what my toenails are for?

Since long before Darwin, we have been inclined to presume that if something serves a purpose, it was more than likely designed in order to serve that purpose, (through evolution in this case). Furthermore, we are of course inclined to interpret purpose in terms of our own frame of reference. That’s why the huge size of an avocado pit seems like such a waste. All that space could have been devoted to more fruit, if the avocado were better evolved.

But you are already ahead of me. It must be that the avocado tree needs such a large pit in order to insure the success of the next generation. Do you know that? Lots of trees get by with much smaller seeds. How do you know that you are not just inferring evolutionary purpose from the result?

You wouldn’t be the first person to do so. Evolutionary biologists spend whole careers doing just that. There is a presumed sanctity to anything that seems to have evolved: it must be the right answer to some evolutionary challenge. Thus starts the debate about whether the genes for ADHD may have begun with, or still serve, some evolutionarily sanctified purpose.

Thom Hartmann and Russell Barkley have been the main protagonists in the debate over whether there is some evolutionary purpose for the ADHD trait. Hartmann suggests that it was an appropriate adaptation for our, pre-agrarian “hunter-gatherer” ancestors. Barkley suggests not, since it clearly causes impairment to modern humans. They are both wrong.

Taking on Hartmann first: his real agenda is to sanctify ADHD traits as purposeful, as part of the evolutionary plan, not just a mistake. However, this is irrelevant even if he were right. Every trait that evolves does so for a specific reason. But that does not confer any intrinsic value to the trait. What if the main evolutionary effect of the ADHD trait is to make young men and women less thoughtful about the consequences of pregnancy? This might increase their evolutionary success, much to the peril of the success of their lives. Their “evolutionary” success does not mean that they have achieved something we will condone as part of the “big plan” or as having human value.

So ADHD, even if reflecting an evolutionary process, may be a liability, particularly in the context of modern culture. However, this perspective, championed by Barkley, has its own flaws. The worst error is its circular logic: ADHD is defined as causing impairment, (in two or more settings no less). Any counter-example of the impairment model of ADHD automatically disqualifies itself, since it is not “real” ADHD without impairment.

But that aside, most traits have their good and bad sides. Just because studies on the impairments of ADHD find such impairments, does not mean that impairments are all that ADHD brings. The gene that causes the crippling disease sickle-cell anemia also protects people from malaria, an infection that kills over a million people every year. Would Barkley say that this was a good trait or a bad one? What is the “purpose” of that gene? Is it to strangle blood circulation, or to protect from malaria?

ADHD does not have a “purpose” anymore than the sickle-cell trait does. Both may have evolutionary advantages, or they may be trials for some future evolutionary turn. But it does not matter. ADHD persists genetically because it has not yet conferred significantly worse reproductive success than some alternative. This is neither an endorsement nor a condemnation by evolution’s “purposefulness.”

Now as an aside, I want to agree that Hartmann’s model is useful for showing people with ADHD that they are not defined by their impairments. There is little chance of successfully treating the problems that ADHD does cause if a clinician is not able to support the many strengths that this same person has. Treating a trait that causes impairment leads to a very different outcome than imagining there is such a thing as “an impaired person.”

Conversely, telling a person with ADHD that they are merely a misunderstood hunter is uplifting, but not helpful. In the end, people want help with the things that are not yet working for them. Call these things whatever you like, but they have to be addressed.

I now want to show you a place where thinking in evolutionary terms can be very enlightening indeed. From the above it is clear that I don’t believe evolution knows what it wants or how to get it. It has no foresight whatsoever, and makes no value judgment about what new genetic twists may or may not be a good idea. It doesn’t even have a purpose. Evolution merely generates what in hindsight, so far, turn out to be relatively good ideas.

How then does evolution work its magic? What it lacks in foresight, it makes up for in creativity and perseverance. (Perhaps evolution has ADHD?) Actually, evolution might be defined as nothing more than creativity and perseverance. Our genes create some new twist, in a blind impulsive way, and then go see if it works out. And then they do it again and again and again for millions of years. If you try enough different things, you are bound to look like a genius eventually.

And there is the part that is evolution’s true lesson. You have to try enough different things. If the human genome had been all “farmers”, I am sure we would have been at a greater risk for extinction at some point in our long history. Or if the genome had been all “hunters” we would be confronted with more impairment now. What evolution needs, wants and must have is diversity. It needs enough different choices.

Since I am only likely to be here for a hundred years at best, I do not suspect that I will see the broad sweep of evolution at the genetic level. However, our culture can also be seen as evolving. Cultural evolution requires the same sort of creativity and perseverance.

Perseverance is likely so long as humans live together in groups. But I would suggest that creativity is in serious jeopardy right now. The ADHD has some promise to maintain that constant flow of new ways to look at things. This does not mean that it is a better way, necessarily. It just means that having choices is always better than not having them. Then when something doesn’t work, you have an alternative.

Neuro-cognitive diversity—having people with different styles of thinking—is likely helpful in maintaining a diverse set of viewpoints in our culture. We can’t say now which perspectives are going to pay off, but the more different ones we have, the more likely that we will have success.

Who knows? Perhaps in a few million years we will learn to use toenails to help pick up a dropped contact lens. Maybe ADHD will become a sought after trait for solving some problem that we cannot even anticipate now. Or maybe not. I’ll just be glad that we have choices.