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    Intelligence and Genetics: Do Some People Inherit an Edge?

    Written by

    Elijah Wolfson

    Image: Betty Lee/Flickr

    Cerys Cooksammy-Parnell is like most 11-year-old girls growing up in Birmingham, England. She likes to text with her friends, she just started learning how to properly play tennis, she's never beaten her father at chess, and her favorite iPhone game is Fruit Ninja.

    There's one thing that makes Cerys stand out from the other pre-teens, though. Cerys is a certified genius, with an IQ estimated to be higher than Einstein's and Stephen Hawking's. Cerys isn't the youngest Mensa member (a two-year-old was admitted earlier this year), but she is the youngest ever documented to attain a perfect score of 162.

    How did Cerys end up in this rarified class of natural intellectual capacity? What makes an 11-year-old—by one metric, at least—smarter than the rest of the world?

    One possible answer lies with her parentage. After all, her father is a former chess champion, a highly successful lawyer, and scored a 142 on the Mensa test, putting him in the top two percent of the population. Did Cerys inherit her intelligence from her dad? Put another way, has she been playing with a stacked deck she was dealt at birth?

    Intelligence, and by extension the intelligence quotient (IQ) test, supposedly appraises not what a person knows, but what a person is able to understand. The underlying theory is that most of our intellectual abilities are based around how we form meaning from patterns.

    IQ is a fairly recent phenomenon, first developed in the 1900s by a Parisian psychologist, Alfred Binet, and adapted to English by Stanford University social scientists after World War II. But these days, its application is widespread: children entering primary school in the US are administered some form of the test to determine whether they will succeed in a normal education program, and on the way out, they are tested again to see where they stand among their peers in terms of college-readiness. The SAT is based on the IQ test and assesses many of the same mental skills. Mensa's version of the test is based on the same concept: pattern recognition.

    Taking a Mensa evaluation requires getting the local chapter to take an official test, but you can take a "workout" online. I took it and scored a 26 out of 30, good for a respectable 87 percent, but definitely nowhere near "genius" levels. My IQ matters. It's likely directed the course of much of my life, just as it will Cerys's.

    "There is nothing else that we have that predicts more things better than IQ," says Robert Plomin, professor of behavioral genetics at the Institute of Psychiatry, King's College London. "It predicts educational ability, occupation status, and even health and longevity. IQ predicts more socially important outcomes in society than anything else."

    But it's also a metric that's taken a lot of heat. Critics believe the IQ test (and its partner, the SAT) inherently penalizes minorities and those who grew up in poor environments, and neglects to account for differing cultural conceptions of intelligence. They say it measures only one type of intellect and doesn't account for creativity or interpersonal aptitude. Some critics, such as Harvard scientist Stephen Jay Gould, reject IQ as an ex post facto metric that reinforces the intellectual supremacy of wealthy white men, more akin to the “scientific racism” of eugenics than to actual science.

    They also believe that by relying on the IQ test and the SAT to determine the future of our children, we are propagating the problematic notion that intellectual potential is innate—that you and I are born with a fixed inheritance that will determine our future, and there's nothing we can do about it. 

    We very openly accept that height, eye color, and other physical traits come from our parents. But the provenance of psychological traits like IQ does not feel nearly as clear cut. After all, you can’t do much about the hair color you were born with. But shouldn’t you be able to study hard, lift yourself up by the bootstraps, and become a success no matter how dense your parents were?

    Yes and no. For decades, scientists argued back and forth, spilling much ink in the debate between whether intelligence was naturally given or the product of nurture and environment. However, in recent years, Plomin said the scientific community has come to the consensus that intelligence is on some level the product of your genes.

    Specifically, IQ is about 50 percent heritable. (For context, height is 90 percent heritable; weight is 70 percent.) A number like 50 percent heritability does not mean that you get 50 percent of your intelligence from your parents, and 50 percent from the environment. It’s a more complex, abstract statistical estimate. Essentially, what heritability estimates is the ratio between how much the range of genetic differences can affect a given trait compared to how much a range of environmental factors can affect that same trait.

    If that sounds complicated, it’s because it is.  To simplify, you can read the number like this: on average, about 50 percent of the individual differences we see in intelligence between different people may be attributable to genetic differences. And that number is well documented.

    "I think there is very little disagreement in the scientific community," said Plomin. "No one even does studies anymore to look at whether intelligence is heritable."

    Outside of the scientific community, though, IQ remains a touchy subject.

    "People don't like to talk about IQ, because it undermines their notion of equality," Douglas Detterman, founder of the research journal Intelligencetold Wired. "We think every person is equal to every other, and we like to take credit for our own accomplishments. You are where you are because you worked hard."

    "No one even does studies anymore to look at whether intelligence is heritable."

    Fifty percent is far from a perfect score, of course, and the environment does come into play. In a 2006 article written for the New York Times Magazine, David L. Kirp, professor of public policy at the University of California, Berkeley, summed up the argument formed by the "nurture" side of the debate. The findings are consistent. "How genes are expressed depends on the social context," he said.

    That is to say, your environment can affect whether you reach your genetic potential. Grow up in a well-off home with supportive parents, and you’ll probably max out. Grow up in an impoverished household, and your genes will be stymied.

    Plomin flips this on its head. "As you go through life, to a great extent, you create your own environment correlated to your genetic propensity," he said. In other words, when certain children grow up surrounded by books, it isn't the books themselves that give them a high IQ. It's the tendencies towards learning (and the ability to learn) that they've inherited from the parents that chose to fill their home with books.

    Either way, environment makes a difference. Likely, the string that combines the two threads of nature and nurture will never be fully unwound. But the reality is that intelligence does have a genetic component, and, at least on an individual level, genetics do matter.

    Not everyone sees the heritability of IQ as a strike against the less advantaged. That same Wired story highlighted another kid genius, Zhao Bowen, who oversees a multi-million dollar genetic research project at China's top biotech institute, BGI Shenzhen. Zhao, now 21, and his team (using data collected by Plomin) anticipate that they are a decade away from being able to screen embryos during in vitro fertilization in order to select the DNA combination that leads to the unborn children with the highest IQ possible. Go in with your spouse, run a few tests, and leave with the knowledge that your unborn child will be smarter than both of his or her parents.

    It's not completely science fiction. Genetic selection for other "undesirable" conditions already happens thanks to prenatal screenings. We can already filter out Tay-Sachs disease and albinism. We can also ensure that newborn babies do not have a dangerous genetic mutation that can raise the risk of breast cancer from about 12 percent to 60 percent. Down syndrome can be detected using DNA samples in the first trimester.

    Realistically, though, we are far from a reality in which we're able to genetically produce super-intelligent babies. There's something called the "heritability gap" in the life sciences, which describes the difference between the genetic influence we can observe and the genes we can identify to account for that genetic influence.

    "For body weight, which is about 70 percent heritable, there are 32 genes that have been identified that account for maybe two percent heritability," said Plomin, whose project The Study of Mathematically Precocious Youth is the source of data for Zhao's genetic study. "There's a very long way to go."

    We are far from a reality in which we're able to genetically produce super-intelligent babies.

    On the other hand, just a few genes can make a huge difference. Using those 32 genes, the study of the cause of obesity has sped up exponentially, and scientists are uncovering scores of new ways to attack the problem. For example, one recent study found a genetic connection between obsessive-compulsive disorder and obesity. Another found that a genetic allele called the FTO gene could be partially to blame for the elevated rates of obesity in Mexican Americans. A third highlighted the possibility that a mutation of the MMP2 gene could cause obesity in women.

    But for all the work that Zhao, Plomin, and others have done to this point, not a single gene has reliably been shown to account for the heritability of IQ. Plomin believes that if we could identify just a few of the genes associated with IQ, we could make huge strides in the field of education.

    "We're not so good at fixing problems once they are full blown," he said. On the other hand, if we could use genetic markers to identify kids who are at high risk for reading and learning disabilities early on, we could feasibly intervene with intensive language therapy at an early age, avoiding costly (and less effective) approaches later in a child's education. We may not be able to change a person's IQ, but we could definitely mitigate the potential negative outcomes of having a lower IQ.

    IQ has real-life consequences, and it's easy to imagine parents in the near future willing to pay to provide this leg up for their offspring. After all, according to Wired reporter John Bohannon, 20 IQ points can be the difference between a high school dropout and a college graduate. Zhao thinks he'll soon be able to promise every child those 20 points.

    Of course, there is one thing that can, and probably will, undermine Zhao's idealism and effort towards IQ equality: economics. Choosing your unborn child's genetic makeup isn't going to be a right. It'll be a luxury, affordable only to the ultra-rich.

    The project may, in fact, end up accelerating social stratification by intelligence. The rich get smarter, and we’re back to where we started. It amounts to the premise of the 1997 film Gattacca: We could end up in a situation where new technologies actually facilitate eugenics and the reification of class and race structure, instead of leveling the playing field.

    Luckily, genetics might not be the only way to maximize your IQ potential. For the low price of $19.95 a month, you can participate in the SMART (Strengthening Mental Abilities with Relational Training) system. SMART’s claims to increase your IQ are backed up by dozen of studies published in peer-reviewed journals and by participant testimonies.

    If that’s too much for your budget, you may be able to find free versions of the so-called “dual N-back” test. Although it can’t increase your IQ, working through test was shown in a landmark 2008 study to improve “fluid intelligence” (the supposedly immutable aspect of IQ) in participants. Lumosity is one well-known “brain game” proprietor that offers free and paid versions of its program. Regardless of the avenue, it's clear that working out your brain can have direct benefits, even without prenatal genetic enhancement.

    And even then, having a high IQ score is only one factor in the way your life is shaped. "IQ isn't the end-all, be-all," said Plomin. It has almost no correlation with happiness, for example. While it has been shown to predict some positive life outcomes, it certainly doesn't guarantee success.

    In addition, Plomin pointed out that even if we were able to screen for IQ during an IVF process, it's not exactly the highest priority. You're more likely to spend the money screening for the approximately 2,000 dangerous and potentially lethal genetic disorders.

    "I think people get very transfixed on just IQ," said Cerys's father Dean, he of the genius-level score. "I'd like to see some different forms of intelligence test that evaluate a broad range of skills, rather than just problem solving and verbal reasoning."  

    Cerys seems to have this wider skill set. She's well spoken, empathetic, and, for example, "loves debate." While her father thinks she may end up as a doctor or otherwise involved in the sciences, Cerys wants to be the head of the Bank of England. And her dad's okay with that. First and foremost, he says, Cerys should be doing something that makes her happy.