Are People Getting Dumber? One Geneticist Thinks So
2012-11-27 0:00

By Rebecca Boyle | PopSci.com

A Stanford geneticist says humans have so many genetic mutations that were less intelligent than our ancestors, and its getting worse. Eugenicists 100 years ago had similar hypotheses.



Theres this great recurring Saturday Night Live skit from several years back where Phil Hartman plays an unfrozen caveman who goes to law school. He pontificates on the American judicial system while marveling at modern technology like the tiny people in the magic box (a TV). It fits a common stereotype: Human ancestors were, well, cavemen, and not as smart as we are today. A provocative new hypothesis from a Stanford geneticist tries to turn this stereotype upside down.

Human intelligence may have actually peaked before our ancient predecessors ever left Africa, Gerald Crabtree writes in two new journal articles. Genetic mutations during the past several millennia are causing a decline in overall human intellectual and emotional fitness, he says. Evolutionary pressure no longer favors intellect, so the problem is getting exponentially worse. He is careful to say that this is taking quite a long time, so its not like your grandparents are paragons of brilliance while your children will be cavemen rivaling Hartmans SNL character. But he does posit that an ancient Athenian, plucked from 1000 BC, would be among the brightest and most intellectually alive of our colleagues and companions.

His central thesis is that each generation produces deleterious mutations, so down the line of human history, our intelligence is ever more impaired compared to that of our predecessors.

Not surprisingly, the hypothesis, published in the prominent journal Trends in Genetics, has several geneticists scratching their heads.

It takes thousands and thousands of genes to build a human brain, and mutations in any one of those can impair that process, thats absolutely true. And its also true that with each new generation, new mutations arise ... but Crabtree ignores the other side of the equation, which is selection, said Kevin Mitchell, associate professor at the Smurfit Institute of Genetics at Trinity College Dublin, who operates the blog Wiring the Brain. Natural selection is incredibly powerful, and it definitely has the ability to weed out new mutations that significantly impair intellectual ability. There are various aspects in these papers that I think are really just thinking about things in a wrong way.

Crabtree said he wanted to examine the cumulative effect of generation-to-generation mutation on intelligence, which is thought to be controlled by many genes. Using indices that measure X-chromosome-related mental retardation, he comes up with between 2,000 and 5,000 genes related to human intellectual ability. Using another index measuring average mutations that arise in each generation of children, he calculates that within 3,000 years, we have all sustained two or more mutations harmful to our intellectual or emotional stability.

There is a general feeling that evolution constantly improves us, but it only does that if there is selection applied, Crabtree said in an interview. In this case, it is questionable about how much selection is occurring now compared to the process of optimizing those genes, which occurred in the jungles of Africa 500,000 years ago.

Theres already evidence for this in other areas, he argues: Take our sense of smell. Humans have far fewer olfactory receptors than other animals, he said--were guided by our intellect now, not by smell. We can think about where a piece of food came from, how it was processed, which plant its from, who has been around it, and so on. A dog, on the other hand, simply sniffs something and either eats it or doesnt.

Once you place pressure on intellectual abilities, and take it off of olfactory abilities, the olfactory genes deteriorate, Crabtree said.

Similarly, he believes evolution now selects for other traits--namely, the most healthy and the most immune, not the most intelligent. Human movement into communities and cities increased the spread of infectious diseases, and those with the strongest physical constitutions survived to pass on their genes, he argues. He said he wanted to publish this hypotheses because geneticists can test for this, in an expensive process that requires saving some genetic information that typically gets discarded.


[...]


Read the full article at: popsci.com













Related Articles


Latest News from our Front Page

No Jab, No Pay reforms: Religious exemptions for vaccination dumped
2015-04-20 20:03
Religious exemptions for childhood vaccinations will be scrapped to toughen Australia’s new “no jab, no pay’’ laws stripping welfare from parents who refuse to vaccinate their children. Social Services Minister Scott Morrison revealed he is dumping the last remaining exemption on the books after holding talks with religious leaders. Just a week after The Sunday Telegraph revealed Mr Morrison was scrapping exemptions ...
Inside David Lynch: An Esoteric Guide to Twin Peaks
2015-04-20 18:24
‘I learned that just beneath the surface there’s another world, and still different worlds as you dig deeper.’ – David Lynch If you’ve ever sensed the flimsy, thin veneer of what parades itself as the good ole US of A, and felt a bit like you’ve been sold a fake, then David Lynch’s Twin Peaks is a series you must see. ...
Third-gender toilet sign – now a reality in Sweden
2015-04-20 18:29
If you don’t identify yourself as a man, a woman or are officially handicapped — where should you go to relieve yourself? In Sweden, the social justice warriors have solved the problem by inventing a third-gender toilet sign. A couple of years ago, the Swedish language was introduced to a new personal pronoun, “hen“, to replace gender specific hon (she) and ...
Feminist goes crazy when compared to Swedish nationalist
2015-04-20 4:56
A picture of a media acclaimed feminist next to a young nationalist girl got real big attention in Swedish media last week. It is “hate” and “mockery” to show the difference between the two, according to the collective Swedish press. When the young nationalist Hanna Lindholm (member of the Sweden Democratic Youth) published a picture on internet, where she compared ...
Massive pollution scandal in Norwegian fjord
2015-04-20 4:53
The Norwegian government today gave the green light to one of the biggest single instances of pollution in the country's history. A new mine will dump its toxic tailings directly into the Førde fjord in the west of Norway. "It is shocking that Norway is the only country in the world allow new projects of this kind", said Lars Haltbrekken of ...
More News »