Human intelligence 'peaked thousands of years ago and we've been on an intellectual and emotional decline ever since'

view gallery VIEW GALLERY

 

Is the human species doomed to intellectual decline? Will our intelligence ebb away in centuries to come leaving our descendants incapable of using the technology their ancestors invented? In short: will Homo be left without his sapiens?

This is the controversial hypothesis of a leading geneticist who believes that the immense capacity of the human brain to learn new tricks is under attack from an array of genetic mutations that have accumulated since people started living in cities a few thousand years ago.

Professor Gerald Crabtree, who heads a genetics laboratory at Stanford University in California, has put forward the iconoclastic idea that rather than getting cleverer, human intelligence peaked several thousand years ago and from then on there has been a slow decline in our intellectual and emotional abilities.

Although we are now surrounded by the technological and medical benefits of a scientific revolution, these have masked an underlying decline in brain power which is set to continue into the future leading to the ultimate dumbing-down of the human species, Professor Crabtree said.

His argument is based on the fact that for more than 99 per cent of human evolutionary history, we have lived as hunter-gatherer communities surviving on our wits, leading to big-brained humans. Since the invention of agriculture and cities, however, natural selection on our intellect has effective stopped and mutations have accumulated in the critical “intelligence” genes.

“I would wager that if an average citizen from Athens of 1000BC 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,” Professor Crabtree says in a provocative paper published in the journal Trends in Genetics.

“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 2,000 to 6,000 years ago,” Professor Crabtree says.

“The basis for my wager comes from new developments in genetics, anthropology, and neurobiology that make a clear prediction that our intellectual and emotional abilities are genetically surprisingly fragile,” he says.

A comparison of the genomes of parents and children has revealed that on average there are between 25 and 65 new mutations occurring in the DNA of each generation. Professor Crabtree says that this analysis predicts about 5,000 new mutations in the past 120 generations, which covers a span of about 3,000 years.

Some of these mutations, he suggests, will occur within the 2,000 to 5,000 genes that are involved in human intellectual ability, for instance by building and mapping the billions of nerve cells of the brain or producing the dozens of chemical neurotransmitters that control the junctions between these brain cells.

Life as a hunter-gatherer was probably more intellectually demanding than widely supposed, he says. “A hunter-gatherer who did not correctly conceive a solution to providing food or shelter probably died, along with his or her progeny, whereas a modern Wall Street executive that made a similar conceptual mistake would receive a substantial bonus and be a more attractive mate,” Professor Crabtree says.

However, other scientists remain sceptical. “At first sight this is a classic case of Arts Faculty science. Never mind the hypothesis, give me the data, and there aren’t any,” said Professor Steve Jones, a geneticist at University College London.

“I could just as well argue that mutations have reduced our aggression, our depression and our penis length but no journal would publish that. Why do they publish this?” Professor Jones said.

“I am an advocate of Gradgrind science – facts, facts and more facts; but we need ideas too, and this is an ideas paper although I have no idea how the idea could be tested,” he said.

THE DESCENT OF MAN

Hunter-gatherer man

The human brain and its immense capacity for knowledge evolved during this long period of prehistory when we battled against the elements

Athenian man

The invention of agriculture less than 10,000 years ago and the subsequent rise of cities such as Athens relaxed the intensive natural selection of our “intelligence genes”.

Couch-potato man

As genetic mutations increase over future generations, are we doomed to watching  soap-opera repeats without knowing how to use the TV remote control?

iPad man

The fruits of science and technology enabled humans to rise above the constraints of nature and cushioned our fragile intellect from genetic mutations.

PROMOTED VIDEO
News
ebooksAn unforgettable anthology of contemporary reportage
Life and Style
Taste the difference: Nell Frizzell tucks into a fry-up in Jesse's cafe in east London
food + drinkHow a bike accident left one woman living in a distorted world in which spices smell of old socks and muesli tastes like pork fat
Sport
Luke Shaw’s performance in the derby will be key to how his Manchester United side get on
footballIt's not a game to lose, writes Paul Scholes
Arts and Entertainment
Don’t send in the clowns: masks and make-up conceal true facial expressions, thwarting our instinct to read people’s minds through their faces, as seen in ‘It’
filmThis Halloween, we ask what makes Ouija boards, demon dolls, and evil clowns so frightening?
News
peopleFarage challenges 'liberally biased' comedians to 'call him a narcissist'
Arts and Entertainment
Liam and Zayn of One Direction play with a chimpanzee on the set of their new video for 'Steal My Girl'
music
Latest stories from i100
Have you tried new the Independent Digital Edition apps?
Independent Dating
and  

By clicking 'Search' you
are agreeing to our
Terms of Use.

iJobs Job Widget
iJobs General

Teaching Assistant

£60 - £65 per day + plus free travel scheme: Randstad Education Cardiff: Teach...

Trainee Recruitment Consultant

£18000 - £30000 per annum + uncapped: SThree: Do you feel you sales role is li...

Maths Teacher

Negotiable: Randstad Education Hull: The JobWe are currently recruiting for an...

PMLD Teacher

£95 - £105 per day + plus free travel scheme: Randstad Education Cardiff: SEN ...

Day In a Page

The drugs revolution starts now as MPs agree its high time for change

The drugs revolution starts now as MPs agree its high time for change

Commons debate highlights growing cross-party consensus on softening UK drugs legislation, unchanged for 43 years
The camera is turned on tabloid editors in Richard Peppiatt's 'One Rogue Reporter'

Gotcha! The camera is turned on tabloid editors

Hugh Grant says Richard Peppiatt's 'One Rogue Reporter' documentary will highlight issues raised by Leveson
Fall of the Berlin Wall: It was thanks to Mikhail Gorbachev that this symbol of division fell

Fall of the Berlin Wall

It was thanks to Gorbachev that this symbol of division fell
Halloween 2014: What makes Ouija boards, demon dolls, and evil clowns so frightening?

What makes ouija boards and demon dolls scary?

Ouija boards, demon dolls, evil children and clowns are all classic tropes of horror, and this year’s Halloween releases feature them all. What makes them so frightening, decade after decade?
A safari in modern Britain: Rose Rouse reveals how her four-year tour of Harlesden taught her as much about the UK as it did about NW10

Rose Rouse's safari in modern Britain

Rouse decided to walk and talk with as many different people as possible in her neighbourhood of Harlesden and her experiences have been published in a new book
Welcome to my world of no smell and odd tastes: How a bike accident left one woman living with unwanted food mash-ups

'My world of no smell and odd tastes'

A head injury from a bicycle accident had the surprising effect of robbing Nell Frizzell of two of her senses

Matt Parker is proud of his square roots

The "stand-up mathematician" is using comedy nights to preach maths to big audiences
Paul Scholes column: Beating Manchester City is vital part of life at Manchester United. This is first major test for Luke Shaw, Angel Di Maria and Radamel Falcao – it’s not a game to lose

Paul Scholes column

Beating City is vital part of life at United. This is first major test for Shaw, Di Maria and Falcao – it’s not a game to lose
Frank Warren: Call me an old git, but I just can't see that there's a place for women’s boxing

Frank Warren column

Call me an old git, but I just can't see that there's a place for women’s boxing
Adrian Heath interview: Former Everton striker prepares his Orlando City side for the MLS - and having Kaka in the dressing room

Adrian Heath's American dream...

Former Everton striker prepares his Orlando City side for the MLS - and having Kaka in the dressing room
Simon Hart: Manchester City will rise again but they need to change their attitude

Manchester City will rise again but they need to change their attitude

Manuel Pellegrini’s side are too good to fail and derby allows them to start again, says Simon Hart
Isis in Syria: A general reveals the lack of communication with the US - and his country's awkward relationship with their allies-by-default

A Syrian general speaks

A senior officer of Bashar al-Assad’s regime talks to Robert Fisk about his army’s brutal struggle with Isis, in a dirty war whose challenges include widespread atrocities
‘A bit of a shock...’ Cambridge economist with Glasgow roots becomes Zambia’s acting President

‘A bit of a shock...’ Economist with Glasgow roots becomes Zambia’s acting President

Guy Scott's predecessor, Michael Sata, died in a London hospital this week after a lengthy illness
Fall of the Berlin Wall: History catches up with Erich Honecker - the East German leader who praised the Iron Curtain and claimed it prevented a Third World War

Fall of the Berlin Wall

History catches up with Erich Honecker - the East German leader who praised the Iron Curtain and claimed it prevented a Third World War
How to turn your mobile phone into easy money

Turn your mobile phone into easy money

There are 90 million unused mobiles in the UK, which would be worth £7bn if we cashed them in, says David Crookes