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 we’re less intelligent than our ancestors, and it’s getting worse. Eugenicists 100 years ago had similar hypotheses.



There’s 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 it’s not like your grandparents are paragons of brilliance while your children will be cavemen rivaling Hartman’s 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, that’s absolutely true. And it’s 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.”

There’s 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--we’re 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 it’s from, who has been around it, and so on. A dog, on the other hand, simply sniffs something and either eats it or doesn’t.

“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

Aurora Shooting Victim Parents Face $200K Court Fees, Bankruptcy, After Failing to Sue Ammo Dealers
2015-08-01 2:17
The 2012 Colorado Theater Shooting still doesn’t add up… Media character and ‘Shooter’ James Holmes in court in 2012-2013. In 2014, Sandy and Lonnie Phillips, the mother and stepfather of Aurora Theater Shooting victim Jessica Redfield Ghawi, tried to sue the ammo companies they believe supplied shooter James Holmes with his ammunition, body armor and other items. They bleived that the online retailer BulkAmmo.com had sold Holmes ...
FBI's Joint Terrorism Task Force Investigating Confederate Flags at MLK's Ebenezer Baptist Church
2015-08-01 2:21
According to the Atlanta Police Department, two White men left four small Confederate Battle Flags outside MLK’s Ebenezer Baptist Church in Atlanta … and get this, the FBI’s Joint Terrorism Task Force is on the scene investigating the incident. Atlanta police Chief George Turner said his agency was working with federal authorities and they have not determined what charges might be ...
Democratic National Committee Chair Wasserman Schultz Can’t Explain Difference Between Democrat Party and Socialism
2015-08-01 2:08
Things got very awkward today when Chris Matthews asked DNC Chair Debbie Wasserman Schultz what the difference was between the modern Democratic Party and Socialism. We haven’t seen that dazed look since Rachel Dolezal was busted as a fraud. Wasserman Schultz was speechless. Completely stumped. Couldn’t answer. Then changed the subject. Because we all know there is no difference between today’s Democrat Party and the radical ...
Catching on slow: Yet Another Study Show Cellphone Radiation Cause Cancer
2015-08-01 1:44
The scientists were right — your cell phone can give you cancer. There have long been whispers of a cancer connection from your cell — and a new study backs up the claims. "These data are a clear sign of the real risks this kind of radiation poses for human health," study author Igor Yakymenko said. Yakymenko’s meta-study — basically a study of ...
Trump Goes #Cuckservative on Immigration
2015-08-01 1:28
For weeks, the media have trumpeted the supposed death of the Trump campaign. First, they claimed, Trump’s campaign imploded on launch thanks to his comments about illegal immigration. Then they claimed that Trump was finished because of his slap at Senator’s (R-AZ) war service. But neither of those comments alienated Trump’s base – he’s maintained his seven point lead over ...
More News »