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.

Start your day with The Independent, sign up for daily news emails
ebooks
ebooksA special investigation by Andy McSmith
  • Get to the point
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

Recruitment Genius: Customer Service Executive

£18000 - £22000 per annum: Recruitment Genius: This is an exciting opportunity...

Recruitment Genius: Retail Buyer / Ecommerce Buyer

£30000 - £35000 per annum: Recruitment Genius: Working closely with the market...

Recruitment Genius: Sales Executive - CAD Software Solutions Sales

£20000 - £50000 per annum: Recruitment Genius: A reputable company, famed for ...

Ashdown Group: Client Accountant Team Manager - Reading

Negotiable: Ashdown Group: The Ashdown Group has been engaged by a highly resp...

Day In a Page

War with Isis: Iraq declares victory in the battle for Tikrit - but militants make make ominous advances in neighbouring Syria's capital

War with Isis

Iraq declares victory in the battle for Tikrit - but militants make make ominous advances in neighbouring Syria
Scientists develop mechanical spring-loaded leg brace to improve walking

A spring in your step?

Scientists develop mechanical leg brace to help take a load off
Peter Ackroyd on Alfred Hitchcock: How London shaped the director's art and obsessions

Peter Ackroyd on Alfred Hitchcock

Ackroyd has devoted his literary career to chronicling the capital and its characters. He tells John Walsh why he chose the master of suspense as his latest subject
Ryan Reynolds interview: The actor is branching out with Nazi art-theft drama Woman in Gold

Ryan Reynolds branches out in Woman in Gold

For every box-office smash in Ryan Reynolds' Hollywood career, there's always been a misconceived let-down. It's time for a rethink and a reboot, the actor tells James Mottram
Why Robin Williams safeguarded himself against a morbid trend in advertising

Stars safeguard against morbid advertising

As film-makers and advertisers make increasing posthumous use of celebrities' images, some stars are finding new ways of ensuring that they rest in peace
The UK horticulture industry is facing a skills crisis - but Great Dixter aims to change all that

UK horticulture industry facing skills crisis

Great Dixter manor house in East Sussex is encouraging people to work in the industry by offering three scholarships a year to students, as well as generous placements
10 best compact cameras

A look through the lens: 10 best compact cameras

If your smartphone won’t quite cut it, it’s time to invest in a new portable gadget
General Election 2015: The masterminds behind the scenes

The masterminds behind the election

How do you get your party leader to embrace a message and then stick to it? By employing these people
Machine Gun America: The amusement park where teenagers go to shoot a huge range of automatic weapons

Machine Gun America

The amusement park where teenagers go to shoot a huge range of automatic weapons
The ethics of pet food: Why are we are so selective in how we show animals our love?

The ethics of pet food

Why are we are so selective in how we show animals our love?
How Tansy Davies turned 9/11 into her opera 'Between Worlds'

How a composer turned 9/11 into her opera 'Between Worlds'

Tansy Davies makes her operatic debut with a work about the attack on the Twin Towers. Despite the topic, she says it is a life-affirming piece
11 best bedside tables

11 best bedside tables

It could be the first thing you see in the morning, so make it work for you. We find night stands, tables and cabinets to wake up to
Italy vs England player ratings: Did Andros Townsend's goal see him beat Harry Kane and Wayne Rooney to top marks?

Italy vs England player ratings

Did Townsend's goal see him beat Kane and Rooney to top marks?
Danny Higginbotham: An underdog's tale of making the most of it

An underdog's tale of making the most of it

Danny Higginbotham on being let go by Manchester United, annoying Gordon Strachan, utilising his talents to the full at Stoke and plunging into the world of analysis
Audley Harrison's abusers forget the debt he's due, but Errol Christie will always remember what he owes the police

Steve Bunce: Inside Boxing

Audley Harrison's abusers forget the debt he's due, but Errol Christie will always remember what he owes the police