Mastering Chess: Genes or Environment?
It is always interesting to look at people who have excelled at something to see what we can learn.
I recently talked about the new research indiating that there are some genes that have some impact on intelligence.
There is an interesting article in today’s New York Times, entited, “Nature? Nurture? Never Mind. Here’s a Sister Act to Watch,” by Dylan Loeb McClain. He has this to say:
“Siblings who are elite chess players are rare. The best known are probably the Polgar sisters of Hungary. Susan, the eldest, is a grandmaster and former women’s world champion. Sofia is an international master. And Judit, the youngest, is the best woman player in history.
Other notable chess-playing siblings have included the Byrne brothers, Robert, a grandmaster and the longtime columnist for The New York Times, and Donald, an international master who died at 45; and Gregory Shahade, an international master, and Jennifer Shahade, a two-time United States women’s champion, who were taught chess by their father, Michael, a master.
Why so few elite sibling players? Is it simply because it is highly unlikely for a single family to produce multiple elite players? Or do most siblings have different interests?
The questions go to the heart of a familiar debate: Is chess talent innate or nurtured?
In his popular book “The Immortal Game,” David Shenk said great chess players were made, not born, writing, “Cognitive chess research punctured the longstanding myth of the chess prodigy, the born genius.”
The best players, Shenk wrote, are the product of intensive study and training. He said the Polgar sisters, who were raised by their father, Laszlo, from an early age to be chess players, were a prime example.
Shenk recounts an episode years ago in which Susan was studying with an international master and they had a problem they could not solve. They woke up young Judit, who, half-asleep, found the solution immediately and went back to bed.
Aren’t the varying levels of talent among the Polgar sisters, who all presumably had the same training, evidence of innate differences? Possibly.
A pair of sisters who have been making a big splash lately do not seem to be separated by ability, at least so far. Nadezhda and Tatiana Kosintseva of Russia are ranked No. 14 and No. 24 in the world among women. But at the European championships, which concluded April 15, Tatiana ran away from a large field, finishing two points ahead of her sister.”
There is undobtedly some set of genes that increase the chance that someone will be good at some game or other, whether it is chess or golf. But there is also the family, school or club that can help someone to realize their true potential.
But even if the genes aren’t all there, you can still become highly competent if you have learned how to learn and if you have learned the arts of patience, perseverance and persistence.
Biology is not destiny!
Genius Genes
I have talked before about the fascinating topic of child prodigies, and the continuing debate about the contributions and interactions of nature and nurture.
There is an important new study published in the journal Behavioral Genetics that should be of interest to anyone interested in thinking, intelligence and optimizing the potential of children.
A team of researchers from Washington University School of Medicine in St. Louis, has gathered the most extensive evidence to date that a gene that activates signaling pathways in the brain influences at least one kind of intelligence. They have confirmed a link between the gene, CHRM2 and performance IQ, that involves a person’s ability to organize thoughts or events logically.
The team found that several variations within the CHRM2 gene could be correlated with slight differences in performance IQ scores, which measure a person’s visual-motor coordination, logical and sequential reasoning, spatial perception and abstract problem solving skills. When people had more than one positive variation in the gene, the improvements in performance IQ were cumulative.
Typical IQ tests also measure verbal skills and typically include many subtests. For this study, subjects took five verbal subtests and four performance subtests, but the genetic variations influenced only performance IQ scores.
The researchers studied DNA gathered as part of the Collaborative Study on the Genetics of Alcoholism (COGA). In this multi-center study, people who have been treated for
alcohol dependence and members of their families provide DNA samples and investigators have isolated DNA regions related to alcohol abuse and
dependence as well as a variety of other outcomes.
Some of the participants in the study also took the Wechsler Adult Intelligence Scale-Revised, a traditional IQ test. Members of 200 families, including more than 2,150 individuals, took the Wechsler test, and those results were matched to differences in individuals’ DNA.
By comparing individual differences embedded in DNA, the team focused on CHRM2, a muscarinic receptor gene on
chromosome 7. The CHRM2 gene activates a multitude of signaling
pathways in the brain involved in learning, memory and other higher
brain functions. The research team does not yet understand how the gene
exerts its effects on intelligence.
Intelligence was one of the first pscyhological factors that attracted the attention of people interested in the interplay of genes and environmental influences. Early studies of adopted children showed that when children grow up away from their biological parents, their IQs are more closely correlated to biological parents, with whom they share genes, than adoptive parents, with whom they share an environment.
But in spite of the association between genes and intelligence, it has been difficult to find specific variations that influence intelligence. The genes identified in the past were those that had profoundly negative effects on intelligence – genes that cause mental retardation, for example. Those that contribute to less dramatic differences have been much harder to isolate.
The St. Louis team is not the first to notice a link between intelligence and the CHRM2 gene. In 2003, a group in Minnesota looked at a single marker in the gene and noted that the variation was related to an increase in IQ. A more recent Dutch study looked at three regions of DNA along the gene and also noticed influences on intelligence. In this new study, however, researchers tested multiple genetic markers.
The lead investigator in St. Louis, Danielle Dick, had this to say,
“This is not a gene FOR intelligence, it’s a gene that’s involved in some kinds of brain processing, and specific alterations in the gene appear to influence IQ. But this single gene isn’t going to be the difference between whether a person is a genius or has below-average intelligence.”
“One way to measure performance IQ may be to ask people to order pictures correctly to tell a story. A simple example might be pictures of a child holding a vase, the vase broken to bits on the floor and the child crying. The person taking the test would have to put those pictures into an order that tells the story of how the child dropped the vase and broke it and then cried.”
“If we look at a single marker, a DNA variation might influence IQ scores between two and four points, depending on which variant a person carries. We did that all up and down the gene and found that the variations had cumulative effects, so that if one person had all of the ‘good’ variations and another all of the ‘bad’ variations, the difference in IQ might be 15 to 20 points. Unfortunately, the numbers of people at those extremes were so small that the finding isn’t statistically significant, but the point is we saw fairly substantial differences in our sample when we combined information across multiple regions of the gene.”
Most experts believe that there are at least 100 genes that could influence intelligence, but it is unlikely that any one gene is going to be the ONE determinant of how smart someone is. After all, IQ itself has very poor predictive value for anything much in life apart from achievement in high school. The many genes involved probably have small, cumulative effects on increasing or decreasing IQ, and the key will be to understand the interaction between environmental influences and these genes. We already know that childhood nutrition, socio-economic status and emotional and cognitive environments have a profound influence on intelligence and achievement. Altogether too many children have all the mental machinery but do not even realize the possibilities open to them.
It is also clear that early influences will have a lot to do with the repertoire of intelligences that a person has. In the book and CD series Healing, Meaning and Purpose I spend some time discussing Howard Gardner’s important concept of multiple intelligences. Many of us have skills in certain domains and it is a terrible mistake to assume that because a child is not very good at logical or verbal tasks, that they are not smart. After all, how many brilliant musicians, computer scientists and entrepreneurs never finished high school or college?
There is clearly more than a gene deciding our intelligence and success at certain activities. The genes may give us the machinery and the fuel, but there are clearly many other factors. I’ve always been a very keen chess player and I once had a friend who was a nationally ranked contract bridge Master. He would destroy most normal mortals at any card game: including me! Even when we played scratch games of contract bridge he would always try to avoid partnering me: he told me that I sucked too badly! 8-(
He also had a hobby: he built and designed all kinds of board games. He used to get upset that whatever the game, if it was played on a board, I almost always won. But here’s the interesting thing: our IQs were virtually identical. But he was murderously good at card games but not at anything involving a board: another refinement of intelligence. I probably did well with board games because I could plan and visualize in three dimensions. My friend had a phenomenal memory for cards that I simply don’t possess.
As the owners of some establishments in Las Vegas once discovered to their glee….
“Intelligence is quickness to apprehend as distinct from ability, which is capacity to act wisely on the thing apprehended.”
–Alfred North Whitehead (English Mathematician and Philosopher, 1861-1947)
“Intelligence is the ability to find and solve problems and create products of value in one’s own culture.”
–Howard Gardner (American Psychologist and Professor at Harvard, 1943-)
“The test of a first-rate intelligence is the ability to hold two opposed ideas at the same time, and still retain the ability to function.”
–F. Scott Fitzgerald (American Writer, 1896-1940)
“To the dull mind all nature is leaden. To the enlightened mind the whole world sparkles and burns.”
–Ralph Waldo Emerson (American Poet and Essayist, 1803-1882)
“It is the sign of a dull mind to dwell upon the cares of the body, to prolong exercise, eating and drinking and other bodily functions. These things are best done by the way; all your attention must be given to the mind.”
–Epictetus (Phrygian-born Greek Stoic Philosopher, c.A.D.55- c.A.D.135)
Madness and Genius Revisited
I must have heard a thousand times that there’s a fine line between genius and insanity. I have talked before about the possible link between the two through schizotypal personality disorder. It is quite well known that there are two living Nobel Prize winners who have a diagnosis of schizophrenia and many more who have first-degree relatives with it.
There is some very interesting research in the current issue of the Journal of Clinical Investigation from a team of scientists at the National Institutes of Health’s (NIH) National Institute of Mental Health (NIMH).
In the latest installment of a story that has been unfolding over the last three decades, they report on their findings concerning a human gene for a master switch in the brain called DARPP-32. Most people inherit a version of a gene that optimizes their brain’s thinking circuitry, yet paradoxically also appears to increase risk for schizophrenia, an illness marked by impaired thinking. The main kinds of thinking involve reasoning, abstraction and creativity.
Over the last two decades, studies in animals, most notably by Nobel Laureate Paul Greengard at Rockefeller University, have established that DARPP-32 in the striatum switches streams of information coming from multiple brain chemical systems so that the cortex can process them. Both the neurotransmitter that DARPP-32 works through – dopamine – and the chromosomal site of the DARPP-32 gene have been implicated in schizophrenia.
The NIMH researchers in this new study have identified a common version of the gene and showed how it impacts the way in which two key brain regions exchange information, so affecting a range of functions from general intelligence to attention.
To understand DARPP-32’s role in the human brain, they used genetic, structural and functional magnetic resonance imaging and also post-mortem studies to identify the human gene’s variants and their functional consequences.
Seventy five percent of subjects had the most common version of the gene, which boosted the activity of circuits in the prefrontal cortex of the brain. This region is the major filter, controller and processor of cognitive information. When active, it increases structural and functional connections and our performance on tasks that involve thinking. It almost certainly does so by increasing gene expression. In 257 affected families, people with schizophrenia were also more likely to have this common version of the DARPP-32 gene.
DARPP-32 appears to shape and control a circuit running between the striatum and prefrontal cortex. The circuit affects key brain functions implicated in schizophrenia, such as motivation, working memory and reward-related learning.
The senior investigator is Daniel Weinberger, who had this to say,
"Our results raise the question of whether a gene variant favored by evolution, that would normally confer advantage, may translate into a disadvantage if the prefrontal cortex is impaired, as in schizophrenia. Normally, enhanced cortex connectivity with the striatum would provide increased flexibility, working memory capacity and executive control. But if other genes and environmental events conspire to render the cortex incapable of handling such information, it could backfire — resulting in the neural equivalent of a superhighway to a dead-end."
Although several groups of researchers have looked for the possible clinical relevance of DARPP-32, they have had much success. This study shows a strong connection between the molecule and human cognition and also, perhaps, with schizophrenia.
What is also interesting about this finding is that it helps provide us with a mechanism by which environmental stress could lead to cognitive problems.
Apart from the uninformed tirades of Tom Cruise, I see a lot of opinion pieces on websites and YouTube expressing the opinion that psychiatry is baseless, ostensibly because there is no science behind it. By anyone’s standards, this is high level science utilizing a series of state-of-the-art approaches. And another piece of evidence that psychiatry is becoming more science than art, linking the mind, the brain and the environment into one harmonious whole.
Does the Spinal Cord Think?
In recent years we have become very interested in the ever-increasing evidence there are large complex neural networks outside the brain and autonomic nervous system. The main ones are in the intestine and the heart. These systems are so complex and well organized that some people have talked about us having a “brain” in the heart and another in the intestine. This may be a bit of an over-statement. For instance the cerebellum at the back of the brain is large and highly complex, but is so arranged that it probably cannot generate conscious experience. That particular trick needs a cerebral cortex that self-organizes, recruits new systems when necessary for some particular task and generates vast oscillations that are modulated by genes and the environment.
Now new research has shown that the spinal cord has some of those same properties that we associate with the cerebral cortex. This groundbreaking work has just been published in the journal Science, and the entire paper is available here.
So why the excitement and interest? It often astonishes me how many students who come to my lectures seem not to have a curiosity gene. And there is so much about which we should be curious. Despite the billions spent on research there is still a great deal about the human body that is not understood at all. Not small esoteric things, but huge questions.
For instance how can some people think and communicate even if most of the brain is destroyed by disease? On the other hand some people are incapacitated by the smallest lesion. I’ve taught neurology for years, in particular the art of neurological examination. I was trained by some of the best in the world, so I know how to look for subtle neurological signs. Yet I’ve seen a great many inexplicable things: I saw someone come to autopsy who had no neurological signs, but had a tumor occupying more than half of the dominant hemisphere of the brain.
Here’s another puzzle: we don’t know how humans are able to move. Our muscles are controlled by thousands of nerve cells in the brain, spinal cord and peripheral nervous system. This entire complex system must work as a whole in order to successfully generate a single motion. Yet how quickly do most children learn to stand and walk. The new research has shown that the spinal cord is not a passive signal conductor, but has instead shown that spinal neurons, while engaged in the network activity underlying movements, show irregular firing patterns similar to those seen in the cerebral cortex. Even if we repeat a certain motion with high accuracy, the nerve cells involved never repeat their activity patterns. Just the same as happens in the cerebral cortex.
This is yet more evidence to suggest that “thinking” does not only go on in the brain. It makes sense to think of the major systems – heart, intestine and spine – as key components of the subliminal, pre-conscious mind. Some people like the term subconscious, but that runs into the confusing problem of mixing up the terms subconscious and unconscious.
I talk about some of these differences and how to work these different parts of yourself in the book and CD series Healing, Meaning and Purpose.
Chiropractors have been telling us for years that the spinal cord is a lot more than just a relay system. It looks as if they may have been correct.
If you are interested in following up on my comments about what it takes for a neural network to generate conscious experiences, you may be interested in having a look at my review of the excellent new book Rhythms of the Brain by Gyorgy Buzsáki. and
The Biology of Beauty
When we think about the characteristics that make someone physically attractive most of us probably think that they are purely subjective and culture bound. But recent evidence suggests that this is not true.
In an astonishingly comprehensive study published in the Proceedings of the Royal Society B: Biological Sciences, Devendra Singh from the University of Texas at Austin has analyzed references to fictional beauties from modern times back to early Indian literature. He found that slimness of the waist was the most common term of praise from an author.
I found it very surprising that this association even seemed to hold in times when a more Rubenesque figure was in fashion.
But I think that the key is not the actual number of inches, but the ratio of waist to hips.I have commented several times that the waist to hip ratio is probably a better physical marker of health risk than body mass index (BMI). Though even this needs to be supplemented by other tests.
Professor Singh’s work has nothing to do with making value judgments, but is instead looking at some of the factors involved in mate selection and this work adds to evidence highlighting the role of the ratio between waist and hips in attracting a mate.
All the recent furor over the dangerously shrinking fashion model has again raised the question that although female waist size has become important in modern Western society and culture – and is likely a factor fueling eating disorders – it is not completely clear whether this waist obsession has always been the case.
In what can only be described as a labor of love, Singh has spent years examining representations of women through history, and in one study, he measured the waist-hip ratio of hundreds of statues from different eras.
In the most recent research, he looked at how "attractive" women were depicted in literature, analyzing more than 345,000 texts, mainly from the 16th to 18th centuries. While most of the writings were British and American, there was a small selection of Indian and Chinese romantic and erotic poetry dating from the 1st to the 6th century of the Christian era.
Singh had this to say: "The common historical assumption in the social sciences has been that the standards of beauty are arbitrary, solely culturally determined and in the eye of the beholder. The finding that the writers describe a small waist as beautiful suggests instead that this body part – a known marker of health and fertility – is a core feature of feminine beauty that transcends ethnic differences and cultures."
Other studies have found a link between a woman’s waist to hip ratio and her fertility which may offer some explanation as to why during evolution it became a factor in selecting a mate. The ratio, like breast size and smooth complexion, is partly under the control of estrogen, which is, of course, a key hormone in the maintenance of fertility.
There has been a great deal of work – and even more speculation – about why men and women are found physically attractive. The idea is that beauty is an indicator of genetic and developmental health. There is also some evidence that physically "attractive" people are healthier than less attractive people.
In 2004 Satoshi Kanazawa and Jody Kovar from the London School of Economics published an intriguing study in the journal Intelligence with the controversial title: “Why Beautiful People are More Intelligent."
The basic idea is that evolutionary processes have, both genetically and socially, led to what we call assortative mating, in which partners have been chosen for their strength, good health and even height: all attributes which have given their possessors a high status. I must be honest that even though I’ve seen the data, when I see and hear some of the comments of a few people in the public eye I still question the association between beauty and intelligence.
There appear to be a few features that characterize physically attractive faces: bilateral symmetry, averageness, and secondary sexual characteristics. Attractive faces tend to be more symmetrical than unattractive faces.
Fluctuating asymmetry (FA) – random differences between the two sides of the face – is usually not found to be attractive. And this may be why: it increases with exposure to parasites, pathogens, and toxins during development. FA also increases with genetic disruptions, such as mutations and inbreeding. Developmentally and genetically, healthy individuals have less FA and more symmetry in their facial and bodily features.
Across many societies around the world, there is a positive correlation between parasite and pathogen prevalence in the environment and the importance placed on physical attractiveness in mate selection. The theory is that in societies where there are a lot of pathogens and parasites it is especially important to avoid individuals who have been afflicted with them when they select mates.
Facial averageness in another feature that increases physical attractiveness: faces with features close to the population average are more attractive than those with extreme features. The evolutionary reasons for why average faces in the population are more attractive than extreme faces are not as clear as the reasons for why facial symmetry is attractive. Some current speculation is that facial averageness results from the heterogeneity rather than homogeneity of genes so that would mean that individuals with average faces are more resistant to a larger number of parasites. Therefore like FA, facial averageness may be an indicator of genetic health and parasitic resistance.
There is good data that infants as young as 2-3 months gaze longer at a face that adults have judged attractive rather than a face judged unattractive. And other research has shown that 12 month old infants exhibit more observable pleasure, more play involvement, less distress, and less withdrawal when interacting with strangers wearing attractive masks, than with strangers wearing unattractive masks. They also play significantly longer with facially attractive dolls than with unattractive dolls.
2-12 months is not nearly enough time for infants to have learned and internalized the cultural standards of beauty through socialization and media exposure. So the research data seems to suggest that the standards of beauty might be innate, rather than learned.
Even though there is all this evidence for a evolutionary and biological factors in beauty, it is a mistake to use such a simple model to try and explain away all of our partner preferences.
By the time that they leave high school, most people have grasped that physical attractiveness is an important first step in attraction, but after that becomes highly
subjective: delightful but not essential.
This work also fails to take into account the attractiveness of factors like radiance, humor, attention, attentiveness, energy, self-assurance, movement, grace and gesture.
Neither can it take account curiosity, presence, charisma, compassion and spiritual awareness. All of these can be extremely attractive, but are hard to explain on simple biological and evolutionary models.
And, by the way, all of these additional factors can be learned: whatever your weight and measurements, whether you are tall or less so and whatever your age.
You can learn to develop many of the things that genetics may have forgotten.
“Beauty awakens the soul to act.” –Dante Alighieri (Italian Poet and Philosopher, 1265-1321)
“Beauty is not in the face, beauty is a light in the heart.” –Kahlil Gibran (Lebanese Poet and Philosopher, 1883-1931)
Leg Length and Cognitive Reserve
I recently mentioned the "Barker Hypothesis" which says that fetal malnutrition is associated with many physical problems later in life.
Well the difficulties may not only be physical.
I would like to tell you about an important concept that we call "Cognitive reserve." This can be thought of as our cognitive resilience. This first came to light almost twenty years ago when a post-mortem study of 137 elderly people was published in the Annals of Neurology, and confirmed something that we had suspected for years: there was a large discrepancy between the degree of Alzheimer’s disease neuropathology and the clinical manifestations of the disease. Some people had extensive pathology but they clinically had no or very little manifestations of the disease. The investigators also showed that these people had higher brain
weights and greater number of neurons compared with age-matched
controls. This lead to the idea that they had a greater "reserve." This is why building your brain throughout life is thought to reduce the ce of cognitive impaitrment later on.
Studies have shown that childhood cognition, educational attainment and adult occupation all independently contribute to cognitive reserve, and more recently it has been confirmed that education and the complexity of a person’s occupation may both slow the rate of decline in people who already have Alzheimer’s disease.
Although height is in part genetically determined, shorter leg length has been found to be associated with an adverse environment in early childhood. In a recent study of older Afro-Caribbean people living in London, shorter leg length was significantly associated with cognitive impairment, leading to the suggestion that shorter leg length may be a marker of early life stressors that then result in reduced cognitive reserve.
It is also worth recalling our discussion about the association between growth hormone and intelligence in children and between intelligence and head size.
And nutrition is one of the determinants of growth hormone synthesis and release.
Naturally this does not mean that less tall people will all get Alzheimer’s disease. But these observations have a number of practical consequences. They re-emphasize the importance of good nutrition during pregnancy: something that is simply not available to over a third of the world’s population. They also help us to identify some of the people who would most benefit from strategies to increase their cognitive reserve and to avoid some of the things that can strip it away from them.
The History of Human Intelligence
There is a wonderful interactive map at Indiana University showing the history of influences in the development of intelligence theory and testing.
This is static picture of what it looks like.
If you click on the name of an individual in this map, you get a potted biography of each person.
If you interested in psychology it’s a great resource.
Enjoy!
Head Size and Intelligence
In August we discussed some of the new data showing an association between the hormone insulin-like growth factor 1 (IGF-1) and a child’s IQ.
Now new research from the University of Southampton in England has found an association between skull size and intelligence. It seems that the brain volume a child achieves by the age of 1 year helps to determine his or her later intelligence.
The study of 633 newborns born at term has found that those with larger heads scored better on intelligence tests at the age of 4. And those children whose heads were larger than the average at age 8 also had higher IQs. Children who put on a spurt of skull growth after the age of 8 did not show a catch up in their IQ scores, implying that there is a critical period for skull growth, brain and cognitive development.
The researchers also studied the babies’ parents. The babies’ mothers completed surveys about their parenting style, their older children, and other factors such as breastfeeding and postpartum depression.
The babies tended to have higher IQ scores if they had been breastfed for three or more months, if their parents had more education and if they had mothers with high scores on the questionnaire that looked at parenting style.
Even after adjusting for all those factors, babies’ head growth by age 1 remained tied to IQ scores among the 4- and 8-year-olds.
It is also known that older people with a larger head circumference tend to perform better in tests of cognitive function and may have reduced risks of developing Alzheimer’s disease. The protective seeds are sown in the first eight years of life. But there is still much that can be done later in life to protect against the development of Alzheimer’s disease.
Two years ago the same researchers showed that there are critical periods in brain growth and cognitive function in children. Brain growth during infancy and early childhood is more important than growth during fetal life in determining cognitive function. And as we have discussed before in my writings about epigenetics, the food that a child eats, the chemicals that he or she ingests and the attitude of his or her parents and peers can all change the way in which their genes function. Positive influences during the first few formative years can have a massive impact on cognitive function throughout life. But even if a child is exposed to an adverse environment, there are still good chances for repairing the damage throughout life.
Biology is not destiny!
“Intellect annuls fate. So far as a man thinks, he is free.”
–Ralph Waldo Emerson (American Poet and Essayist, 1803-1882_
Brain Growth
Something strange happened to our ancestors. Between about 100,000 to 35,000 years ago, their brains began to grow enormously.
There have been many theories as to why this happened, from climatic change to a change in diet. Some foods contain chemicals that can stimulate the growth of neurons. And yes, there are also those who claim that some external agency caused the sudden growth of the brain, a la Arthur C. Clarke’s 2001: A Space Odyssey.
But what is exciting is that the growth in the brain may still be going on today.
It is clear that the brain is constantly changing. This growth, change, development and regression does not only occur during development, learning or aging, but also over generations. It is often said that the modern human brain is identical to that of Stone Age man, but that is almost certainly not true. If you were to meet a person from 5,000 years ago, they would probably seem quite unintelligent, because all the things that you have learned have stimulated your cognitive abilities. This stimulation also stimulates the formation of the brain. Recent studies of the genetics underlying brain development have shown that the human brain has changed significantly over the last few thousand years.
A study in the journal Science has taught us something new. The investigators studied the gene Microencephalin (MCPH). When the gene is active it causes a severe reduction in brain size coupled with mental retardation. Remarkably, despite this abnormality, there is an overall retention of normal brain structure and a lack of overt abnormalities outside of nervous system. The function of MCPH in healthy humans is less well known.
What makes this study interesting is the finding that the MCPH has changed during the past ~37.000 years, and that the spread has been fast: there has been a strong positive selection for this gene, indicating that the brain has continued to evolve even in more recent times. This is exceedingly important. I have many times emphasized that human beings are changing extremely rapidly.
There is no reason to assume that the evolution of the brain has stopped, and there is every reason for thinking that this gene is one of the mechanisms of change in response to the environment. It is now key to understand all the modulators of MCPH activity. Is it food, stress or environmental stimuli?
Another recent study in the journal Nature analyzed human chromosome 8, and looked specifically at two regions called the major defensin (DEF) gene cluster and MCPH1. The authors also speculated that these regions have played a significant role in the expanded brain size that can be observed through hominid evolution.
At the end of the article, the authors say something very interesting:
“The majority of the genes in the region of high divergence in distal 8p play important roles in development or signaling in the nervous system. Notably, the extremely large CSMD1 gene, which lies at the peak of divergence and diversity, is widely expressed in brain tissues. High regional mutation rates and positive selection are generally assumed to be distinct, but it is possible that the former may facilitate the latter by increasing the rate of appearance of potentially advantageous single, or interacting, alleles. It is intriguing to speculate whether the accelerated divergence rate of this region has contributed to the rapid expansion and evolution of the primate brain.”
For people who are less familiar with this kind of science-speak, let me translate. The study of chromosome 8 should open a whole new field of enquiry about what makes the human brain special. Comparing this region with DNA from other species and from early humans, we will be able to study the relative contribution of these genes to brain size.
Though size isn’t everything (!). The key is to understand the impact of changes in brain size and brain complexity on cognitive processes. In general, there’s a good correlation between intelligence and the volume and complexity of specific regions of the brain.
These new genes and their rapid – and continuing – spread is fascinating. But there are some other things that also differentiate the “naked ape” from other primates. One of the most striking is the large amount of fat that we have in out subcutaneous tissues and in our brains. We also have more of the excitatory amino acid glutamate in our cerebral cortices than chimpanzees or gorillas.
There is much more to be learned, but the consequences for understanding our origins and potential treatments for neurological illnesses are just stunning.
