Are Humans Getting Dumber?

The smart get dumb and the dumb get dumber.Reality television would suggest that people are getting dumber, my recent foray into the genre excepted, of course. In general, I’ve found that it is a postmodern anthem to talk about the disappointments and failures of humanity. A friend, Douglas Hicton of Canada’s Greatest Know It All AND Jeopardy fame, recently showed me this article. Of course, I went ballistic, which was probably Doug’s aim in the first place (incidentally – a friend suggested I give up swearing for Lent. He probably then paid off Doug to show me this article.)

In, Jedidiah Becker discusses recent research in his very well written “The Descent of Man: Why One Scientist Thinks that Humans are Getting Dumber.” Mr. Becker also links to the original research article, which I love, which is available on the author’s site, which I also love. That article, published recently in Trends in Genetics, is: “Our Fragile Intellect” by Gerald Crabtree (Crabtree, 2013. Trends in Genetics, 29:1). Here Dr. Crabtree presents a persuasive argument that is, unfortunately, predicated on a couple very bad assumptions.

Dr. Crabtree correctly points out that our highschool understanding of genetics, that one gene leads to one trait, is incorrect and oversimplified. In fact our genes interact in a very complex way to give rise to our different traits. This isn’t as big a surprise as he’s making out – we’ve known this for a long time because if there were only one gene for height, with two possible forms (alleles) the world would be made of short people and tall people and no middling heights at all. We’ve long known it doesn’t work like that. Intelligence, being as complex as it is, would naturally have many genes that contribute to it. He goes on to talk about how having lots of genes working on one trait means that that trait is likely to be pretty robust to mutations. Also true. But robustness is a really tricky concept. Planes are robust. They have lots of backups to keep disaster from happening, but disaster does happen sometimes. Genetic robustness, the idea that genomes have backups that protect from mutations, goes back to the seminal work of C.H. Waddington in 1942, but the really exciting work on it has been done in the last 15 years. Research is now showing that genomes are in fact robust, but much like ecosystems, mutations can have large effect if they hit the right target. This does not mean that the trait is fragile, or a chain, it just means that like an airplane, the right malfunction can bring the whole thing crashing down.

This is a distinction that Crabtree glosses over. He used the example of a number of mutations on the X-chromosome that cause intellectual defects (wallmart genes). There are quite a few. He then goes on to extrapolate that because there are quite a few of these genes that have a big effect on intelligence when mutated, that a) intelligence is not robust in the same way other traits are and b) intelligence genes on other chromosomes behave the same way. For the reasons stated above, this is a big stretch.

Not only that, but he attributes the bewildering number of genes that have an effect on intelligence as being a sign that all these genes are there SOLELY to control development of intelligence. This is also not likely. Think of the brain – our most metabolically expensive organ: it requires a lot of fat, a big investment in blood flow, oxygenation, and immune surveillance. It stands to reason that genes that are metabolically important can have effects on intelligence if mutated. One of the genes he talks about is probably one of these: “Many of these genes appear to function indirectly, such as the subunits of nBAF chromatin regulatory complexes, which are global transcriptional regulators. This highlights that a gene need not be functionally brain or even human-specific to be essential for our specific human intellectual abilities” (Crabtree, 2013). A fantastic rebuttal of the paper comes from Kevin J. Mitchell, from the delightfully named Smurfit Institute of Genetics, Trinity College Dublin, who also points out that intelligence may actually be just as much a result of good health as an individual trait. He also takes issue with the idea that intelligence is genetically fragile, writing my new favorite sentence in the scientific literature: “It would seem bizarre that evolution would go to such lengths to craft a finely honed human genome over millions of years only to let all hell break loose in what Woody Allen calls his second favorite organ.” (Mitchell, 2013).

Even if the idea of intelligence being genetically fragile were supported, I would have a very hard time believing the evolutionary argument. Crabtree begins his article with the very compelling idea that “if an average citizen from Athens of 1000 BC were to appear suddenly among us, he or she would be among the brightest and most intellectually alive of our colleagues and companions.” The supposition from this argument is that in the ensuing 3000 years we have devolved in intelligence. This represents 100-150 generations, far too short a number of generations to see wholesale changes in our genome. It also makes the stunning assumption that selection on intelligence stopped as soon as the golden age of Greece ended. This may be a classically appealing argument, but from a population genetics standpoint, it does not hold water. When civilizations collapse selection gets more intense, so intelligence should have been selected FOR. Indeed, the popular argument these days is that intelligence doesn’t matter because our rampant love of safety keeps many idiots from winning Darwin awards.

This is probably the argument that makes me the craziest – again this idea of Man being a fallen angel, a disappointment to our early promise. In modern days the incarnation of this idea is that we are no longer under selection to be intelligent, thoughtful, or caring. It’s an idea that has no biological support (see Mitchell’s brilliant rebuttal) and is, as I pointed out earlier, too easy. If we decide that we’re no longer smart, no longer up to the challenge of being thoughtful, intelligent, responsible or caring, if we succumb to the defeatist attitude that we are mindless animals with no potential for greatness, then why bother trying at all?


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