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Code rage: The “warrior gene” makes me mad! (Whether I have it or not)

The views expressed are those of the author and are not necessarily those of Scientific American.


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Mel Gibson in the film BraveheartJust when you think the blame-it-on-our-genes craze can’t get worse, the "warrior gene" goes viral. The latest media outlet to flog it is the Dr. Phil show, which on April 4 broadcast "Born to Rage?". From the promo: "Scientists believe they may know why some people are quicker to anger than others. A new study suggests that inside a rageaholic’s DNA, ‘a warrior gene’ may be pulling the strings. Could today’s guests be genetically predisposed to fits of fury?"

Dr. Phil, a psychologist whose real name is Phil McGraw, presented three "rageaholics"—including Lori, a self-described "Tasmanian devil," and Scott, a reality-TV star and "bully"—as well as Rose McDermott, a political scientist at Brown University and warrior gene researcher. McDermott claimed that the warrior gene, which occurs in about 30 percent of the population, makes you more likely to engage in "physical aggression".

Dr. Phil had the rageaholics tested, and guess what? They all had the warrior gene! "This is information to know that you are more susceptible, at risk for, and predisposed—like someone who is fair-skinned and will burn more readily in the sun," Dr. Phil sagely informed his guests. "It doesn’t mean they need to go through life sunburned. They take precautions to protect against that." The Tasmanian devil sighed, "It’s a relief there’s something linked to this anger, and it’s not brought on because I want to do it."

Dr. Phil’s Web site links to a company called FamilyTreeDNA, "the leading direct-to-consumer DNA testing company in the world. " Send a cheek scraping to the company and it will tell you if you have the warrior gene for $69—$99 if you don’t go through Dr. Phil’s Web site.

This cheesy talk show is hardly alone in hyping the warrior gene. In fact, Dr. Phil borrowed his headline from a recent National Geographic broadcast, "Born to Rage?", which also explores "the disturbing possibility that some people are born to rage." The show follows Henry Rollins, a self-described former punk rocker with a nasty temper, as he interviews "outlaw bikers, mixed–martial arts fighters" and other tough guys and, once again, McDermott. ABC News jumped on the bandwagon last December with an interview with McDermott, who stated: "In many, many studies [the warrior gene] appears implicated in behaviors that look like they’re related to physical aggression or some kind of conduct disorder."

The story of the warrior gene dates back to the early 1990s, when several groups reported a link between violent aggression and a gene on the X chromosome that encodes for an enzyme called monoamine oxidase A (MAOA), which regulates the function of the neurotransmitters such as dopamine and serotonin. The correlation first emerged from studies of a large Dutch family whose male members were mildly retarded and extremely violent. Two were arsonists, one tried to run over an employer with a car, another raped his sister and tried to stab the warden of a mental hospital with a pitchfork. The men all lacked monoamine oxidase A, suggesting that they possessed a defective version of the MAOA gene.

Later, other researchers reported a correlation between violent aggression and an allele of the MAOA gene, MAOA-L, that produces low levels of the MAOA enzyme; the correlation was reportedly stronger if carriers had experienced some sort of trauma as children. The MAOA allele occurs in apes and Old World monkeys as well as in humans, leading to speculation that the allele arose 25 million years ago in the common ancestor of these primates and was subsequently favored by natural selection. In a May 4, 2004, article reviewing all this research, Science dubbed the MAOA allele "the warrior gene," the oldest reference I have found to the term.

Race, inevitably, reared its head. In 2007 Rod Lea and Geoffrey Chambers, researchers at Victoria University of Wellington in New Zealand, reported that MAOA-L occurs in 56 percent of Maori men. "It is well recognized," the researchers commented in The New Zealand Medical Journal, "that historically Maori were fearless warriors." The researchers’ racial profiling was based on a study of 46 men, who needed to have only one Maori parent to be defined as Maori. Lea and Chambers reported that MAOA-L was less common among Caucasians (34 percent) and Hispanics (29 percent) but even more common among Africans (59 percent) and Chinese (77 percent).

In 2009 Kevin Beaver, a criminologist at Florida State University, claimed that males with MAOA-L are more likely to report being gang members (pdf). But his study also showed that the vast majority of MAOA-L carriers are not gang members; moreover, about 40 percent of the gang members were not MAOA-L carriers. Like McDermott, Beaver was featured on the National Geographic show "Born to Rage?"

The 2009 study by McDermott and four colleagues, "Monoamine Oxidase A Gene (MAOA) Predicts Behavioral Aggression Following Provocation," which triggered much of the recent publicity given to the warrior gene, was published in Proceedings of the National Academy of Sciences (PNAS). The article claimed that MAOA-L carriers were more likely than noncarriers to respond with "behavioral aggression" toward someone they thought had cheated them out of money they had earned in a laboratory test. "Behavioral aggression" was defined as making the putative cheater consume hot sauce.

Even disregarding the issue of whether giving someone hot sauce counts as "physical aggression," McDermott’s study provides little to no evidence for the warrior gene, because the difference between carriers and noncarriers was minuscule. McDermott et al. examined 70 subjects, half of whom carried the warrior gene. The researchers found that 75 percent of the warrior gene carriers "meted out aggression" when cheated—but so did 62 percent of the noncarriers. Moreover, when subjects were cheated out of smaller amounts of money, "there was no difference" between the two groups.

Obviously, the warrior gene cannot possibly live up to its name. If it did, the whole world—and China in particular, if the racial statistics cited above are remotely accurate—would be wracked by violence. The warrior gene resembles other pseudo-discoveries to emerge from behavioral genetics, like the gay gene, the God gene, the high-IQ gene, the alcoholism gene, the gambling gene and the liberal gene. (See my previous columns on the liberal gene and gay gene.)

The abysmal record of behavioral genetics stems from two factors. First, the quest for correlations between thousands of genes and thousands of traits and disorders is prone to false positives, especially when traits are as squishy as "aggression" and "childhood trauma" (the variable that helps some researchers link MAOA-L to violent behavior). Second, the media—including respected scientific journals like Science and PNAS as well as shows like Dr. Phil—are prone to hyping "discoveries" that will attract attention.

The media’s fascination with the warrior gene recalls the lurid claims made decades ago concerning "XYY syndrome," in which men are born with two Y chromosomes instead of one; the syndrome affects about one in a thousand men. In the 1960s British researchers identified nine men who had an extra Y chromosome and had a record of violent outbursts. This correlation was not surprising, because the men were all incarcerated in a mental hospital for violent patients. Other researchers, also focusing on institutionalized patients and criminals, quickly claimed to have found evidence that XYY men were hyperaggressive "supermales" at risk of becoming violent criminals.

The XYY-supermale claim was propagated by The New York Times and other mainstream media, enshrined in biology and social science textbooks, and even written into plots for films, novels and television shows (as Wikipedia‘s excellent entry on XYY syndrome documents). Meanwhile, follow-up studies of noninstitutionalized XYY men failed to corroborate the initial claims. In a 1993 report "Understanding and Preventing Violence" the National Academy of Sciences concluded that there is no correlation between the XYY syndrome and violent behavior. In 2007 CSI: Miami nonetheless broadcast a show, titled "Born to Kill," which featured a serial killer with an extra Y chromosome.

Unlike, say, multiverse theories, unsubstantiated claims about human genetics can have real-world consequences. Racists have seized on warrior gene research as evidence that blacks are innately more violent than whites. In 2010 defense attorneys for Bradley Waldroup, a Tennessee man who in a drunken rage hacked and shot a woman to death, urged a jury to show him mercy because he carried the warrior gene. According to National Public Radio, the jury bought this "scientific" argument, convicting Waldroup of manslaughter rather than murder. A prosecutor called the "warrior gene" testimony "smoke and mirrors." He was right.

Photo of Mel Gibson in the film Braveheart courtesy of Wiki Commons

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  1. 1. MarkHenryC 6:32 pm 04/26/2011

    Nice touch, including a pic of Mel, although I think he harbours a variation called the Arsehole gene.

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  2. 2. edyong209 6:34 pm 04/26/2011

    You’ll find no argument from me that the "warrior gene" label need debunking, and that the media makes too much of such trite deterministic labels. I made similar arguments in a feature I wrote on MAOA for New Scientist.

    But I take serious issue with the idea that this somehow reflects badly on behavioural genetics as a field. It’s a bizarre straw man attack – you’re criticising the field because it’s results are not consistent with an incorrect media construction that you yourself have debunked! The media uses a silly deterministic label, and they’re wrong. The underlying science does not support the silly deterministic label… so it’s wrong too?

    Research on MAOA now suggests that the environment affects how the gene influences behaviour. For example, as you write, children who carry MAOA-L AND come from abusive homes have a higher risk of aggressive behaviour; that’s not true if they come from more stable backgrounds. Likewise, the hot sauce experiment found that people w/ MAOA-L are more likely to mete out punishment when they are provoked – another case of nature via nurture. It’s sad that the fascinating area of gene-environment interactions isn’t discussed at all in the piece.

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  3. 3. jtdwyer 1:58 am 04/27/2011

    The article states:
    "Second, the media–including respected scientific journals like Science and PNAS as well as shows like Dr. Phil–are prone to hyping "discoveries" that will attract attention."

    Journalistic credibility is suspect when a publication owned be the Nature Publishing Group can only reference a competing publication, for some reason not Nature, when giving an example of a negative editorial characteristic. Is it being asserted here that Nature is not also guilty of ‘hyping "discoveries" that will attract attention?’

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  4. 4. David N'Gog 8:18 am 04/27/2011

    Behaviour is surely something that can not be controlled by a single gene; however, one should not completely rule out the gene as being legitimately a factor in behaviour.

    It is that- one factor amidst many- and we may be far from discovering all the factors.

    We can’t profile against people with this gene- because alone it means very little- but it may be a block in understanding how our genes combine with environment and other genes to form who we are.

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  5. 5. GAry 7 9:05 am 04/28/2011

    One more predisposing gene? Will the argument of nature vs nurture never end?

    I am quite familiar with rage. It is a response to frustration and stress however, even the most enraged human still has the choice of how to APPLY that rage, either by beating the crap out of a farging icehole or merely punching a hole in a door and THAT derives from social re-inforcement and conditioning.

    In older, pre-technological cultures, there was a social system in place to re-inforce the importance of self control, which was usually emplaced by a "manhood test". In some societies, failing the manhood test meant one was not "human" and could therefore be "food". In others it meant expulsion from the tribe(with a resultant reduction in reproductive potential). The ability to control our base emotions was what defined us as "human". These days, our "manhood test" may involve no more than the keys to the family car,,,

    Baboons are one of the most aggressive apes on the planet. Had these critters developed nuclear bombs, planet earth wouldn’t have lasted a week. I think our historical(and religious) emphasis on the power to choose how we will behave is the basis of our humanity. Even the most violent among us can choose to apply their rage to inanimate objects. If they don’t, though they may walk upright and speak, they’re really not,,,human,,,

    Gary 7

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  6. 6. cccampbell38 1:23 pm 04/28/2011

    I think that Gary 7 has made an excellent point: we humans have more power to choose our response to stimuli than other animals. And No, the nature/nurture argument will never end. The actual workings of the human brain and mind are far too complex for us to be able to propose anything like definitive answers to the etiology of specific human behaviors just yet. The irony may be that the brain/mind may be so complex that it/they are ultimately incapeable of understanding themselves. Be that as it may, the nature/nurture argument has moved toward the influence of nature in the last few decades and should this trend continue it will pose some very interesting moral and legal questions for humanity.
    Oh yes, in stating that rage is a response to frustration and stress, correct, but don’t forget fear. The old "fight or flight" response that we learned about in high school psyc. fifty years ago may be responsible for more anger than we care to admit. Speaking only for myself, I feel anger mostly in response to a situation where I feel am not in control of the outcome. That produces fear, then anger. How often does that occur with others?
    Also, as we live in an uncertain world, are some of us in a more or less constant state of low level fear that tends to leave us on the edge of anger most of the time without our even realizing it?
    Ah, there is so much yet to be learned.

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  7. 7. ormondotvos 2:01 pm 04/28/2011

    "Obviously, the warrior gene cannot possibly live up to its name. If it did, the whole world–and China in particular, if the racial statistics cited above are remotely accurate–would be wracked by violence."

    Uh, been in the ivory tower very long? Ever looked at a playground?

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  8. 8. bucketofsquid 4:54 pm 04/29/2011

    I’ve seen a variety of playgrounds with a variety of ethnicities and it is rarely the high rate of MAOA asians and africans that are raging. It is the low rate of MAOA whites that are usually doing the raging. Thus proving that the "warrior gene" is nothing of the sort.

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  9. 9. bucketofsquid 4:59 pm 04/29/2011

    "Dr Phil" would have done a better service to his guests and audience by suggesting that if they have a lot of anger or problems controling their temper then they should take anger management classes. He should have completely ignored an unsubstantiated claim that hasn’t been peer reviewed and replicated in double blind studies.

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  10. 10. ormondotvos 6:03 pm 04/29/2011

    Gawd, can you miss a point!

    The world IS full of people expressing rage, frustration, etc.

    We act on the predispositions our culture cultures.

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  11. 11. J. Potts 6:13 pm 05/1/2011

    Genetic explanations for this sort of behavior are often facile. The preponderance of social scientific research shows that it is a set of specific situations that lead to violent behavior (e.g. torture). Moreover, much research has also shown the deleterious effects of rage or so-called "warrior gene" phenomenon on those who carry our violent acts. For more on this check out "Violence Workers," the "Lucifer Effect" or for contemporary examples (which are both revealing and tragic) see the recent book "None of Us Were Like This Before."

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  12. 12. jaundyrose 1:28 am 05/5/2011

    I like this article.
    ——
    <a href="http://www.cheapcarinsurance.org.uk">CheapCarInsurance.org.uk</a&gt;

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  13. 13. nooffensebut 11:25 am 07/21/2011

    1)You’re an idiot.
    2)You already admitted that the extreme form, called Brunner syndrome, results in extreme violence.
    3)There is no such thing as a MAOA-L gene. This label is given to both the 2R and 3R alleles. 2R doubles the rate of violence without needing an environmental interaction mechanism. 5% of black men have 2R. Chinese people do not have 2R. 0.5% of white people have 2R. At least those “racists” understood this distinction. By the way, the article you cited by “racists” sourced their information from my previous blog, which was re-posted on my new blog and was based on the original peer-reviewed studies.
    4)The fact that “racists” are better informed on this issue than you is not a reason for MAOA to not affect violent behavior. In fact, you did not cite a single study that shows it has no effect.
    5)The difference between 3R and 4R may be milder, but it is well documented, and I created a handy table explaining this. You (see #1) focused on only one study.
    http://theunsilencedscience.blogspot.com/2010/01/no-amore-for-maoa-from-maori.html
    6)No one is claiming that MAOA is the only violence gene, but it is a violence gene. Beaver included it among 5 genes to create a crude genetic index that affected violent behavior among black men more than the childhood relationships with their mothers.
    7)Further research is improving our understanding of MAOA, which is likely to show that the gene has more effect on violence than previously thought. For instance, a second promoter was just discovered. This is news to you (see #1) because apparently you do not do your homework prior to spouting off about how an entire field of research has an “abysmal record.”
    8)Sorry that I am responding to this stupid essay so late, but the same essay has been written by so many other stupid people. It is hard to keep up with you morons. Needless to say, I would not regularly read your crap.

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  14. 14. jessc217 1:14 am 06/27/2012

    This is a very interesting and informative article. I really enjoy reading it. I have heard of the “warrior gene” before and I also know that it is the MAOA gene. However, I never really know that is the function of the MAOA gene and how this gene affects our behavior. Furthermore, I did not know that “researchers identified men who had an extra Y chromosome and had a record of violent outbursts”. However, I am not sure what it means. Does it means that MAOA gene is expressed more often in the these XYY male? Or some gene that only exists in the Y chromosome can activates the MAOA gene? If so, does this mean male are genetically designed to be violent than female? It is interesting to know that there are genes that are linked to our behavior. I have been reading some of the “behavior genes” study, so I do started to believe that our genes do play a role in our behavior. However, nature versus nurture theories have long been debated. Many researches are now suggesting that the environment also have an effect on our behavior. I guess nobody can say how much these genes affects our behavior, nobody can say that our gene a hundred percent dominates our behavior.

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  15. 15. scientificamericansucks 12:57 pm 05/10/2013

    “even more common among Africans (59 percent) and Chinese (77 percent)”

    It wasn’t 77%, moron. Where’s your correction? It was 77 control subjects. You do this for a living?

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  16. 16. Alt Del 3:35 pm 08/10/2013

    @Scientificamericansucks, That was a separate study of Taiwanese men with 77 control subjects, the 77% frequency with a round up of a CI frequency of 66-88% was from the New Zealand Medical Journal that did it with conjunction to a study of Maori men, learn to differentiate between different studies and different samples.

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  17. 17. johnhorgansucks 10:35 am 08/11/2013

    @Alt Del
    Wrong!
    If you look to the right side of Table 1 in Lea and Chambers from The New Zealand Medical Journal, it makes clear that the Chinese data comes from Lu et al, 2002. Also, see the number “6″ from the paragraph before the table, which refers to Lu et al. Table 1 from Lu et al shows that the control sample size is 77 and the 3R allele frequency is 54.5%. Lea and Chambers switched those two numbers and created a confidence interval of 66-88% from them. The MAOA bibliography at The Unsilenced Science has tabulated many studies into a table for racial allele frequencies. So far, out of 2,552 total Asian alleles, the MAOA-3R frequency is 59.7%. Lea and Chambers were wrong, Steven Pinker was wrong, and now Adrian Raine also repeated this error in his book. Of course, John Horgan is wrong, but I am wrong to even mention his name among a list of actual scientists. Horgan is an embarrassment to Scientific American.

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