I laughed out loud when I saw the many news reports today about the latest articles by Stanford developmental biologist Gerald Crabtree, MD. Not because the reports were wrong or because the research is poor. It’s just that the topic is guaranteed to make nearly anyone either laugh or cry — particularly someone (ahem, ME) who has recently been feeling less and less smart with each birthday.
Crabtree hypothesized in two articles published today in Trends in Genetics that humans are slowly accumulating genetic mutations that will have a deleterious effect on both our intellect and emotional stability. The reason, he believes, is the relative lack of selective pressure during the past 3,000 years. He begins boldly:
I would wager 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, with a good memory, a broad range of ideas, and a clear-sighted view of important issues. Furthermore, I would guess that he or she would be among the most emotionally stable of our friends and colleagues.
It’s an intriguing point. I’ve recently been re-educating myself about ancient Greek history,and I’ve been newly amazed about the breadth and depth of the philosophy and ideas propounded by people thousands of years ago.
Crabtree calculates that between 2,000 to 5,000 genes are likely required to maintain optimal intellectual acuity and emotional well-being. Extending his theory, it’s likely that we’ve each accumulated at least two harmful mutations during the intervening millennia. (Case in point? I just had to look up how to spell that last word.) Why? Well, according to Crabtree:
It is also likely that the need for intelligence was reduced as we began to live in supportive societies that made up for lapses of judgment or failures of comprehension. Community life would, I believe, tend to reduce the selective pressure placed on every individual, every day of their life. Indeed that is why I prefer to live in such a society.
Don’t we all? But although it’s disheartening to think that we’re locked in a downward spiral, it’s way too soon to panic. Crabtree emphasizes that our demise will be slow:
However, if such a study found accelerating rates of accumulation of deleterious alleles over the past several thousand years then we would have to think about these issues more seriously. But we would not have to think too fast. One does not need to imagine a day when we could no longer comprehend the problem, or counteract the slow decay in the genes underlying our intellectual fitness, or have visions of the world population docilely watching reruns on televisions they can no longer build. It is exceedingly unlikely that a few hundred years will make any difference for the rate of change that might be occurring.
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