Tuesday, November 20, 2012

Are We Really Getting Dumber? Not Very Likely

In a recent pair of articles published in Trends in Genetics ("Our Fragile Intellect," Parts I and II), Gerald Crabtree has argued that we are not nearly as intelligent as we were 3000 years ago (he estimates that we all carry at least two gene mutations arising during that time that makes our intellect of emotions less stable).

Here is the offending quote
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.
Here is more about his argument (The Register UK) - the papers are pay-walled.
"The larger the number of genes required" to carry out everyday tasks, Crabtree writes, "the more susceptible we are as a species to random genetic events that reduce our intellectual and emotional fitness."

Recent advances in genetic research, he says, have shown that "the number of genes required for normal human intelligence and abilities might be surprisingly large" – between 2,000 and 5,000 needed for full intellectual and emotional function.

Crabtree cites studies that have shown that genetic mutations are more common than previously thought, and that "a gene need not be human or brain specific in its function to be essential for our specific human intellectual abilities," due to the fact that genes function as links in a chain, and that "failure of any one of the links gives rise to deficiency."

Those deficiencies add up "Within 3000 years or about 120 generations," he says, "we have all very likely sustained two or more mutations harmful to our intellectual or emotional stability."

Crabtree disputes the idea that nature is a self-improving system. "One could argue that anything that occurs in Nature must be good for us," he says, "but this line of reasoning is quite incorrect."

So, if we're losing our intelligence, how did we get it in the first place? "Needless to say," he writes, "this is one of the most important questions of modern anthropology and the subject of much investigation and debate."

Although Crabtree freely admits that proposing answers to that question is "outside my comfort zone," he speculates that humans' expanding prefrontal cortex allowed the development of profound intellectual abilities earlier than is commonly thought.

"We seem to be forced to the conclusion that life as a hunter gather required at least as much abstract thought as operating successfully in our present society," he believes.

"Surprisingly," Crabtree writes, "it seems that if one is a good architect, mathematician or banker, these skills were an offshoot of the evolutionary perfection of skills leading to our ancestor's survival as nonverbal, dispersed hunter-gathers."

Well, then – if we humans were so smart back then, when did we start losing our intellectual and emotional abilities through gene mutation? According to Crabtree, the slide began when we began living in cities, and genetic selection began to focus more on such things as disease resistance rather than the improvement of abstract thought. As support for this argument, he cites the genetic principle that as an organism selects highly for one trait, other traits are selected against.

"It is also quite likely," he says, "that the need for intelligence was reduced as we began to live in supportive, high-density cities that made up for lapses of judgment or failure of comprehension."

In other words, our intellectual and emotional capabilities decayed because they weren't as important for survival.
As one might expect, not everyone (anyone?) agrees with Crabtree. Here are links (and a taste of) two different rebuttals.

From my perspective, anyone familiar with Ray Kurzweil's theory of exponential progress (law of accelerating returns) will understand that - daily - we process hundreds of times more information (at least) at an unconscious level (not even including the information and decisions we process at a conscious level) than an Athenian likely processed in a month (or more). As Kurzweil reminds us, "So we won’t experience 100 years of progress in the 21st century — it will be more like 20,000 years of progress (at today’s rate)."

Fragile intellect or fragile arguments?

Why Gerald Crabtree's speculations about declining human intelligence are wrong

Life before Reality TV. Plato’s Academy mosaic from the Villa of T. Siminius Stephanus in Pompeii (1st century CE). Image: Public domain
It has often been observed that scientists, some rather brilliant, can get things hopelessly wrong when they stray outside their field. Examples are legion, and it has been dubbed the Linus Pauling effect:
The phenomenon is a familiar one: let's call it "the Linus Pauling effect." A highly respected and honored senior scientist, largely out of the mainstream and not up to date with the recent developments (and perhaps a bit senile), makes weird pronouncements about their pet ideas – and the press, so used to giving celebrities free air time for any junk they wish to say, prints and publishes it all as if it is the final truth.
Normally this happens when, say, a physicist starts thinking too hard about brains, but embarrassingly for me (one of my many sins is to be a geneticist), geneticists have a penchant for this too. What is really embarrassing is that more than one has made this mistake with a pet idea about genetics. I will now admit that I am going to step outside of my area of expertise (particularly with respect to human evolution and psychology), so if you are more knowledgeable in these areas, you can have some fun correcting my mistakes.

. . . . A couple hot-off-the-press articles published in Trends in Genetics have been garnering more attention than they're worth. In them, molecular geneticist Jerry Crabtree puts forward an argument that human cognitive abilities are declining:
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. I would also make this wager for the ancient inhabitants of Africa, Asia, India, or the Americas, of perhaps 2000–6000 years ago.
. . . Crabtree fails to analyse the problem correctly.

. . . Crabtree argues that human intelligence has been declining, and remarkably, it has nothing to do with reality TV. Instead, his argument is that if we have lots of genes involved in intelligence, then it's fragile because if one gene "breaks" – mutates – everything goes awry and we become stupid. As the number of genes increases, it is more probable that one of those genes will mutate, and we know that each person carries roughly 60 new mutations in their genomes anyway. (Yup, it is generally accepted that we are all mutants. Collect your superpower on the way out.) 
Read the whole article.

* * * * *

We're Probably Not Getting Dumber

By Neuroskeptic

. . . . Crabtree's argument in a nutshell:

Part I, he outlines the latest evidence showing that many thousands of genes contribute to human cognitive ability, and that because mutation rates are high (higher than previously believed), any given individual probably carries harmful variants of many of these genes. This is quite possibly true ,and interesting, but by itself it's nothing to do with declining IQ.

Part II, Crabtree says that during human evolution, all of these genes were under strong selection pressure because any human or proto-human who wasn't smart enough to hunt, fight and survive in the stone age environment, would get eaten by a predator or starve. However, after these hunter-gatherer tribes became settled farming communities (in say 6000 BC), they were no longer so vulnerable, so the less intellectually able could live... and breed... leading to ever-more unintelligence genes.

Now, there's a lot of problems here. Many have said that this is all a bit like
eugenics, and indeed it is, but that doesn't necessary mean it's wrong... no, it's wrong because the argument is flawed.

For instance, it's already been pointed out that, even if it recently got easier to stay
alive, that doesn't mean it's got easier to get laid lots and have lots of kids; and sexual selection is a powerful force in evolution, perhaps even stronger than survival, and it probably favours higher intelligence.

However, there are other issues.
 Read the whole article.
Post a Comment