Is evolution making us dumber and dumber?

MoJo Musings

My mother and I once had an argument. Actually, we had many arguments but the one I’m talking about involved a hypothetical situation. I argued that if you took a whole lot of people from 2000 years ago and plonked them in our time, they would be able to pick up all the technology we use and have the same intelligence as we do. Even though she couldn’t use the video recorder, she argued that they wouldn’t be able to cope and would have lower intelligence.

I always thought our discussion was pretty obscure but I have just read that, in the absence of my mother, others have carried on the argument.

Professor Gerald Crabtree from Stanford University opens the first of two papers in Trends in Genetics with the following words.

“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.”

He argues that would be the case if the person were taken anywhere from Africa, Asia, India, or the Americas from about 2000 to 6000 years ago.

According to Crabtree, in the last 3000-odd years (approximately 120 generations) we have all accumulated 2.5 to 6 mutations in the 2000 to 5000 genes that are supposed to control our intellectual and emotional capacity. He proposes that because we no longer have to hunt to survive, the natural selection that increased our intelligence is no longer at play.

All genes come in pairs, and if one of ours develops a mutation we can always hope that the other will take up the slack (unless it is a dominant mutation). If one gene is mutated and the other is not, it is not usually such a big problem until the mutations evolve and occur in both genes of the pair (homozygosity). But Crabtree says that the human nervous system is quite sensitive to moves towards homozygosity and our intelligence is quite fragile.

A major counter-argument from GrrlScientist and Bob O’Hara is that selective pressure on our intellect was because of a need for social interaction, rather than hunting. Some pretty dumb animals are very good at hunting and some pretty smart animals are highly social (for example, dolphins).

Andrew Brown argues that intelligence has been on the rise and “the real selective pressures have nothing to do with intelligence, but with resistance to disease, and parasites, and hunger.”

You’ll need to read the articles to get the whole picture, but no doubt the argument will continue.

My mother and I just had to agree to disagree.

Image credit: jurvetson on Flickr

References

Crabtree GR (November 13 2012) Our fragile intellect. Part I. Trends in Genetics http://dx.doi.org/10.1016/j.tig.2012.10.002

Crabtree GR (November 13 2012) Our fragile intellect. Part II. Trends in Genetics http://dx.doi.org/10.1016/j.tig.2012.10.003

2 thoughts on “Is evolution making us dumber and dumber?

  1. Pingback: Our 8th – Receding – Sense: Dumbness | Tea with a Pirate

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