Shrinking Brain in Humans

Scientists are alarmed by shrinking of the human brain

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A study published earlier this year confirmed what scientists have long believed to be the case – the human brain is shrinking.  For more than 7 million years the hominid brain has grown increasingly bigger, almost tripling in size.  But for the last 10,000 years, the human brain has been shrinking at an alarming rate and no one really knows why. New research has attempted to answer this question by examining size changes in specific regions of the brain.

The study published in the American Journal of Physical Anthropology was carried out by a team of Chinese researchers who looked at over 500 endocasts from the past 7,000 years. Endocasts are moulds of brains created from the imprints on the inside of the skull. They are an invaluable resource when studying human evolution, allowing us to track how our brain has evolved over the past few million years.  The results confirmed what has long been suspected – our brains are getting smaller.

 

It was in 2010 when researching a skull that belonged to a Cro Magnon man that scientists first discovered the brain of our ancient ancestor was significantly larger than humans today. This has been replicated time and again and it can now be said that the human brain has decreased from 1,500 cubic centimetres (cc) to 1,350cc, irrespective of gender and race.  If we continue on this path, we will end up having the same-sized brain as Homo Erectus, an ancient human species which had a brain of 1,100 cc.

Does a smaller brain mean less intelligence?

Scientists have been debating for many years about whether a smaller brain means less intelligence, and no agreement has been reached.  To clarify, it is not simply the size of the brain that is relevant here, but the size of the brain in relation to body size, referred to as the Encephalization Quotient (EQ).  Research has found a close relationship between intelligence and EQ. 

Over millions of years, the hominid body has been shrinking but the worrying fact is that our brains are shrinking faster than our bodies. Does this mean human beings are getting dumber, or are smaller brains not necessarily bad?

The human brain is shrinking faster than the shrinkage of the body

The human brain is shrinking faster than the shrinkage of the body. Image credit: Superscholar.org

Many scientists have argued that bigger doesn’t always mean better.  Duke University anthropologist Brian Hare says "the decrease in brain size is actually an evolutionary advantage" because it could indicate we're evolving into a less aggressive animal. For example, the common chimpanzees have bigger brains than bonobos, but they are less likely to resolve issues through teamwork because they're more aggressive. 

Other proponents of the ‘bigger isn’t better’ hypothesis have argued that our ancestors had a larger visual cortex because good vision was necessary for survival. But as social support increased, vision became less important. Those with smaller visual cortexes had more resources available for social regions of the brain, thus increasing chances of survival.

However, the findings of the new study conducted in China are not consistent with these theories because the results indicated that it was not one particular area of the brain that was shrinking – the whole brain has been getting smaller. If the hypothesis about the visual cortex was correct, we should see shrinkage only in that region of the brain.

The one exception is the frontal lobe, which actually seems to be increasing in size. The frontal lobe is the region of the brain responsible for speaking, comprehending the speech of others, reading and writing. It is possible that we are doing a lot more of that now – at least the reading and writing part – compared to our ancient past.

While plenty of hypotheses have been put forward to justify the shrinking of the human brain, there remain many who are less optimistic. The authors of a study published in 2012 maintained that humans lost the evolutionary pressure to be smart once they formed agricultural settlements. 

"A hunter-gatherer who did not correctly conceive a solution to providing food or shelter probably died, along with his/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. Clearly, extreme selection is a thing of the past," the researchers wrote in the journal article published in the journal Trends in Genetics.

More than 4,000 years ago, great civilizations existed around the world and the ancient inhabitants built incredible buildings and cities with great precision and beauty, often with astronomical alignments that we are only just beginning to realise. Nowadays, technology has taken over, rendering our need to apply skill, creativity, and memory virtually redundant. Instead of memorising navigational routes we switch on our ‘sat navs’ and rather than storing phone numbers and addresses in our memory banks, we have them all to hand on our iPhones and Blackberries.  Our technology is evolving rapidly, but sadly it seems that we are not.

Comments

P.S about We use glasses instead of exercizing our eyes" many refractive errors are due to shape of cornea not muscle only some of them are from using near subject but only small % of all refractive errors. that why you exercise cant do anything and glasses dont cause that your vision will detorate look at studies which research that.

Roberto Peron's picture

I think it more likely intelligence has to do with how  the brain is wired and not brain size.  If my hypothesis is true then it doesn't matter if our brains are shrinking or not as we may end up with a streamlined brain size that is super-intelligent.  Ah our next stage in human evolution!  Love it!!

Then again, if my hypothesis is wrong then we are all destined to become total idiots and that means our species is DOOMED!  Yes DOOMED I tell ya!!!  LOL

Oh well, I'm off to swing in some trees again.

 

johnblack's picture

The brain size is linked to intelligence. And the human beings are becoming more and more stupid. In the past decade the IQ in western countries has dropped about 2 points and that is significant. This is just a sample article – food for thought.

http://www.huffingtonpost.com/2013/05/22/people-getting-dumber-human-int...

"The brain size is linked to intelligence" yes showing that smallest is more efficient. In past comment I give reference to article Your reference is little flawed first they use reaction time test so its only one from many aspects and in this aspect can be so many confounding factors wich falws results like time when the test was performed weather and many others. They also claim that: "Western countries conducted between 1889 and 2004 to estimate the decline in g that may have resulted from the presence of dysgenic fertility"

As I wrote smallest brain can be due to reorganization of white matters and grey matter (when teenage brain develop mature it lose grey matter) this is because is create conectivity good example are professional gaming players they have less matter in brain regions which allow them to be a good player but they are more effective than control group, due to connectivity. P.S in my country I hold MD in neurology and toxicology so this is not only my hobby but also profession.

One fragment from article which I reference "But the downsizing does not mean modern humans are dumber than their ancestors -- rather, they simply developed different, more sophisticated forms of intelligence, said Brian Hare, an assistant professor of anthropology at Duke University.
He noted that the same phenomenon can be observed in domestic animals compared to their wild counterparts.
So while huskies may have smaller brains than wolves, they are smarter and more sophisticated because they can understand human communicative gestures, behaving similarly to human children.

From studies we can conclude that average people are less inteligent but this is due to increased borns in families with lower inteligence. Good example my co-workers many of them dont have childrens but my olders from high school frends who did not go to college have average 2 childs.

johnblack's picture

Darek, no matter the degrees you have ... this won't change the fact the brain size is linked to intelligence. Maybe not 100%, but it is linked. Don't forget that our big step in evolution as humans was doubling our brain capacity... Of course brain size also depends on the body size.

You brought the example with huskies being more intelligent. That is also not true. Been able to communicate with humans and adjust to human behaviour does not make them more intelligent, because during this process they have lost major skills that wolves have.

There is no proof for what Brian Hare suggests (and there will never be), it is just a theory.

Now back to humans, having no major change in human body size and suddenly our brains beginning to shrink … then this becomes an issue. And it is a fact the IQ is decreasing, it is not a matter of debate.

The less you use your brain the smaller it becomes, that’s also plain evolution theory (devolution in our case) – whatever is not needed is discarded.

There is plenty of research linking the brain size to intelligence. Here is another example:

http://www.livescience.com/19692-genes-brain-size-intelligence.html

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