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

Love the comment : maybe because we are becoming less aggressive ? Have they looked at the all the conflicts around the world? Modern society has become too sit on the sofa watch garbage which for the most part is stupid, targeting the lowest of ethics oversexed and mind-numbing or sitting at a computer for 8 hours, and the trolls who sit in a darken room and stare at multiple screens for days on end. if the zombies ever attack----humankind may not survive and I hate to say this -- a concentrated - one goal species LOL

Given that (a) yes, brain size makes a demonstrable difference in current human intelligence.
And given that (b) it's unclear whether our brains are getting smaller or whether more of the smaller humans are breeding in cities. (which appears to be the case since cities are genetic and IQ sinks). And given that (c) we have been selecting for immaturity for 10K years (paedomorphic selection). And given that (d) women generally possess superior verbal skills and weaker modeling skills despite smaller brains.

I would hypothesize that all of the above are driving down AVERAGE brain size.
I would suggest we will saw additional paedomorphic selection domestication up and until the period of 'Peak Human' which I suspect was around 1500 bc.
And that at present we are seeing a rapid expansion of dysgenic classes, tilting the data dramatically.
Unfortunately I suspect that the initial shift caused by the adoption of general rules (science) rather than rules of specific cases (recipes), as well as the reduction in the malnutrition at the bottom (left) of the curve, means that the downward shift in genetic iq and brain size from underclass reproduction is being hidden by the flynn effect. But in real terms, on average we are getting smaller, more verbal brains, and a lot more dumb people breeding.

It is widely scientifically accepted theory that our brains grew particularly large due to the new predominant food source once our ancestors were caught in geological and climate change of East Africa. Previously predominantly plant eating omnivores in dense jungle (like other apes), our ancestors encountered life in now dry savanna, with very little fruit and mainly grass or grass-eaters available. Homo Robustus made evolutionary choice of becoming grass eater. Brain did not grow in that species and it got extinct. Our ancestors chose to eat more grass-eaters. Becoming predominantly meat-eating omnivores. By all scientific accounts a positive feedback loop established from this that led to our advance: eating more meat->growing larger brain->using larger brain to get even more meat->even larger and more capable brain...
What happened about 10000 years ago? Agriculture. Food processing (before that time humans not only couldn't collect enough say, grains from the wild to cover the energy spent in the effort but neither than or now can we eat it without processing). Move to food based more in grains than meat. Certain large amount of proteins in the diet is required for having a larger brain. Now we have different challenges such brain might address but the core of the new change is in the diet, food, not lack of evolutionary challenge and selection.

Peter Harrap's picture

Observe how creatures with small brains do things we are unable to do. Birds fly, bees fly, even though theoretically OUR brainy scientists say they should not be able to! There are insects with dozens of legs, their brains can separately control-think about it!- and creatures who have more sense faculties than us. Can you see a mouse from a mile up in the sky!?

So the idea from our brains that the size of our brains matters is somewhat dickheaded, if you’ll pardon my French, or is it Bulgarian?

 

Dont you just love reading how creative some of these comments are, such as Aliya's? So free thinking is still very much alive and well despite some of the comments to the contrary.

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