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The Genetic Fatality of What You Are

11 sept

This morning while checking my Twitter feed, I stumbled upon a tweet on the "internet addiction gene". My reaction was: "Have pity. Please". Thankfully, some people have had spare time to write and dismiss such a scientific breakthrough. It is perhaps a question of timing — all the very recent hysteria about how ENCODE unveiled the indispensability of "junk DNA" just got a bit on my nerves. I’ve written about this elsewhere, so would prefer to skip it here and focus on the ultimate honour for people like me (i.e., geneticists): identifying "the gene of [insert some word here]".

Actually, I’m pretty committed to do all my best and discover no "gene of". Before coming to the concrete reasons why, let me list the top ranking "gene of" below.

The gene of homosexuality

There were people who believed (ok, many still do…) that homosexuality is a disease. Biology came to say there were actual differences in the brains of homosexual and straight people. Then, people started to question the evolutionary basis of homosexuality: ok, it exists, but at constant low rate and additionally, homosexual couples cannot biologically have children together. So, how come "evolution has kept this"? Some people even noticed that female relatives of gay men have children at a higher rate than other women do. Etc., etc.

Researchers thus came up with the idea that genes should play a role in determining such patterns. Here you go with an explanation of male homosexuality by the sexually antagonistic selection. This complicated thing means that a given gene can reproductively benefit one of the sexes but brings harm to the other. It’ll just be regulated differently depending on the sex you consider. Thus:

We show that only the two-locus genetic model with at least one locus on the X chromosome, and in which gene expression is sexually antagonistic (increasing female fitness but decreasing male fitness), accounts for all known empirical data. Our results help clarify the basic evolutionary dynamics of male homosexuality, establishing this as a clearly ascertained sexually antagonistic human trait.

In plain English, male homosexuality is determined by a gene which persists (and is passed down to the offspring) because it promotes high procreation rates among gay men’s female relatives. Before getting to the genetics of female homosexuality, let’s think a bit. The guys here use some Bayesian approach for their model and conclude all this very complicated stuff. They even suggest an example where real data would fit their simulation: if you’re a straight man, the reproductive pattern among your aunts will (on average) reverse the pattern seen among gay men’s aunts. In other words, your paternal aunts will have kids at a higher rate compared to your maternal aunts. The authors check this prediction with the available data and find it holds.

You can find other predictions to make or other existing data to use when challenging such a prediction. Let’s proceed to the female homosexuality thingy though. Clearly, this model doesn’t account for gay women. So, what about a female gay gene? Sorry, ladies, it is a guy-only thing: for girls, it is all in the hormones. (Thankfully, the people ruled out any issue with the brains of lesbians while finding the male gays have "feminized brains".) As with many things, one could assume that if you give an appropriate hormonal cocktail to the person, it may actually reverse the observed characteristics. Hold on: guys in Oregon have tried to defeminize sheep through feeding them with hormones.

Credit: <a href="http://www.flickr.com/photos/mishism/3080405903/">mishism on Flickr</a> (CC-by 2.0)

The gene of humour

Girls don’t make funny jokes, everyone knows it. Only men do. You wondered why? Come on, it is nature: testosterone makes people funny. So, as men have higher testosterone rates, they are naturally funnier. Ok, it is not a gene stricto sensu, but this doesn’t matter: secretion rates are somewhat genetically controlled anyway.

The gene of happiness

Here is our revenge, gals: men are funny, but we are happy! This is now scientifically proven that the "gene of happiness" is not operating in males. Indeed, the gene MAOA (stands for "mono-amine-oxidase type A") codes for an enzyme degrading monoamines. This family includes dopamine and serotonin which are nothing else than the "happiness molecules", their synthetic equivalents are used in a number of anti-depressive drugs. So, studies have found that depressed people have lower than average rates of these monoamins. Thus, the current study finds that the low expression of MAOA was related significantly to greater happiness in women. Makes sense huh: less you express this gene, less you have the resulting enzyme that naughtily degrades your happiness molecules. Authors modestly pinpoint that their findings "may help explain the gender difference on happiness." I didn’t know there were any but now that we have the solution, we must have a problem it solves…

The gene of friendship

I love this one. People used statistics to establish that the gene DRD2 (associated with alcoholism) is found in people who stick together. Conversely, the gene CYP2A6 (associated with xenometabolism, that is metabolism of foreign bodies such as nicotine) was found to be divisive. In other words, CYP2A6 carriers tend to stay away of each other. The authors discuss this:

[...] regardless of the causal mechanism, homophily and heterophily on a specific allele is especially noteworthy because the phenotypes with which these genes are related are likely polygenic (they are affected by many genes) and the genes are also likely pleiotropic (they affect many traits).

(Definitions: in the study, homophily = friends with the same genotypes; heterophily = friends with different genotypes, respectively.)

Aha, so, in plain English, we have no explanation whatsoever but stuff certainly does a lot and affects other stuff. Impressive.

 The gene of liberalism

Don’t laugh on the above, please. It is more serious than you may imagine. The August 2012 issue of much-respected Trends In Genetics published a detailed review on "The Genetics of Politics: Discovery, Challenges and Progress". Genes do influence your behaviour AND your political affiliation. You thought the "gene of liberalism" is a joke? Of course, not: the DRD4 gene is found in youth who have liberally-minded friends. Explanation brought to you by ScienceDaily:

Previous research has identified a connection between a variant of this gene and novelty-seeking behavior, and this behavior has previously been associated with personality traits related to political liberalism.

Lead researcher James H. Fowler of UC San Diego and his colleagues hypothesized that people with the novelty-seeking gene variant would be more interested in learning about their friends’ points of view. As a consequence, people with this genetic predisposition who have a greater-than-average number of friends would be exposed to a wider variety of social norms and lifestyles, which might make them more liberal than average. They reported that "it is the crucial interaction of two factors — the genetic predisposition and the environmental condition of having many friends in adolescence — that is associated with being more liberal." The research team also showed that this held true independent of ethnicity, culture, sex or age.

If you hate [black/Arab/Jew/put a racistic-sexist-homophobe word here] people, there is nothing you can do about it: it is your genes, stupid.

The gene of internet addiction

This one was just awesome. Some dudes found a correlation between the very famous "happiness molecules" I already mentioned above and "internet addiction". I don’t know about you, but this kind of sensationalism gives me pimples, from the red scratching ones. Very nicely brought to you for free (reading this ground-breaking study if you don’t have subscription to the journal would cost you $49, the joy of paywalls): the German team have interviewed 843 people about their Internet habits, and 132 of them revealed abnormal habits. More precisely, all these disturbed men and women have problems handling the internet: all their thoughts revolve around it during the day, their wellbeing said to be severely impacted if they have to go without it.

Plasma bottle. Credit: D. Endico on Flickr (CC-by-SA 2.0)

Plasma bottle. Credit (CC-by-SA 2.0)

Wow, a real 2.0 pandemics is in the making. It is even worse than you thought: it is in your genes. Actually, a mutation in the CHRNA4 gene is responsible for this problematic behaviour, the study finds. Also, gals are more affected than boys, which is in contradiction with many other previous studies having reported men are more prone to be internet addicts than women. Whatever.

The funny thing is that this gene is known to be involved in nicotine addictions. No need to rewrite what is written elsewhere:

[...] the main point is this: the biochemical mechanisms (including genes) involved in chemical addictions will naturally be the mechanisms involved in habit formation more generally since habit formation is what they were originally designed for. So when this German scientist announced triumphantly that a gene which seems to have a modest correlation with heavy internet use is a gene that may play a role in nicotine addiction he had told us (1) nothing that should surprise anyone; and (2) nothing that settles the question of whether this heavy internet use deserves to be called an "addiction" or merely a "habit." Either way, whether it’s a habit or an addiction, it is going to involve pleasure-dispensing biochemical mechanisms of the sort that can get us addicted to such chemicals as nicotine and cocaine–because, again, it is through such pleasure-dispensing mechanisms that habits in general form.

It reminds me the "Bad Science" Baroness Susan Greenfield mindblowing stances that internet affects our brains possibly causing autism and that wicked computer games can cause dementia in kids

The rape-proof gene

I left the best for the end: you may recall the huge controversy sometime ago on how women have evolved adaptive responses to the threat of rape. Yeah, the "evolutionary psychology" rhetorics strikes back with its inimitable rant. The vocabulary implies that there is genetics underlying all this since changes within genes and genomes are the substract of evolution. This was nauseating. I will actually bias the links here by pointing you not to the original article but to a response to it by an evolutionary biologist.

Ok, and so what?

This is somewhat frustrating to read all that above and to feel the sarcasm without clearly having an idea what the point is, huh. Honestly, it physically hurted me to read some of these articles. So much idioty is really challenging to handle.

What do all these fabulous news tell us? Evidence is so scarce, our attempts to make everything biologically defined to give it a (allegedly) rational meaning are however persistent. What is then the social impact when saying that a behaviour has a biological/genetic fundament? Please welcome: "the stigma gene".

10 years ago, people asked students how they would consider a potential partner who has some mental disorder. The study consistently confirmed that "the public tends to reject biological and genetic explanations of mental health problems in favour of psychosocial explanations focused on negative life events. It also confirmed previous findings (contrary to the assumption on which most destigmatisation programmes are based) that biological and genetic causal beliefs are related to negative attitudes, including perceptions that ‘mental patients’ are dangerous, antisocial and unpredictable, and reluctance to become romantically involved with them." Later on, the work on destigmatization continued with another project where young dudes’ reactions were measured "before and after a video portraying a young man with psychotic symptoms followed by either biogenetic or psychosocial explanations. Consistent with previous studies, the "medical model" approach significantly increased perceptions of dangerousness and unpredictability." Another study concluded similar things: "The biological causes (‘brain disease’ and ‘heredity’) were less frequently selected for depression than for schizophrenia. Irrespective of place and type of mental disorder, endorsing biological factors as the cause of schizophrenia was associated with a greater desire for social distance, the same relationship applies to depression in half the instances."

Clearly, "mental illness is an illness like any other" doesn’t help reducing the negative stereotypes. Ok, so what’s the link to "the liberalism gene" or "the homosexuality gene"? Well, it seems pretty straigtforward to me: if you assume that being depressed/right-wing/homosexual/whatever is a fatality in your genes, how open-mindedly will you address the incriminated people? Knowing that nothing can be done to change this because "it is the genes!", how likely are you to get into a relationship with someone having a given genetic predisposition? How likely are you to have a kid knowing his father has been hyperactive (also claimed to be genetically determined)? You as a parent may very well decide to "take the risk" having a child with a partner with such (alleged) predisposition but what about teachers? Those are often told they are not responsible for hyperactive kids because it is a biomedical condition. You can have an easy excuse for everything, from your girlfriend being too picky about rape jokes (women lack humour…) to a serial killer diagnosed with I don’t know what genetic variant causing him schizophrenia.

A genetic determination of social behaviour implies limits. Some of them may be positive: if your kid’s teacher is gay, you don’t need to worry s/he will "contaminate" the youth. You find such a thought disgusting? Me too. But having a behaviour defined by a gene implies the cultural and social environment can do nothing on it. You cannot culturally eradicate the minority with such a gene. Additionally, if you consider the male homosexuality explanation above, you can see it in a different way: the sexually antagonistic selection explanation is actually a reproductive benefit for the women whose close male relatives are gays. This makes the whole phenomenon much more entangled and interwined, right? The authors of the "male homosexuality evolution" study above say:

This point of view may help shift the focus away from male homosexuality per se: rather than concentrating on the sole aspect of the reduced male fecundity that it entails, we can place it within the more general framework of a genetic trait with gender-specific benefit, which may have evolved by increasing the fecundity of females. A consequence of this is that the entire population exhibits a high fecundity variation, and, as we show, the trait can neither disappear nor completely invade the gene pool.

You cannot just limit the genetic determination on a given minority because it finally affects the population as a whole. And leaves the male homosexual individuals with the honourable fate of a byproduct of female reproduction success. Awesome.

Talking about a biological determination and homosexuality, mind the case of lesbians. These are "only" physiologically affected, that is some chemical intervention would reverse it. Some fancy bishop said: "If a biological basis is found, and if a prenatal test is then developed, and if a successful treatment to reverse the sexual orientation to heterosexual is ever developed, we would support its use". Of course, it’d be no difference with screening for Down Syndrome, right? You think I’m paranoid, well, have a look at UNICEF’s statistics on pre-natal child selection per sex. If you were engaging into research to defeminize a sheep’s brain, what does it mean studying gay sheep?

Having a given gene is not like having blonde hair you can always taint in brown: you have it forever, it is accepted as a fixed given. You become the victim, the sick deserving special care. BUT it is also beyond anyone else’s control, it is totally your problem. And here you go in a weird magical circle where you are the only responsible for your state and anything can be expected from you including the worst. Whatever the worst is because it is a moral value and the problem with moral is that it is always someone else’s. How easy is the leap between a major badly considered behaviour (homosexuality, money pathology, political inclinations) and its "cure" in dedicated centers?

P.S. Neurosexism

As a bonus, I suggest you a have a look at this worth-all-your-attention list of neurosexist pieces:


ResearchBlogging.org
Articles:

James H. Fowlera, Jaime E. Settle, and Nicholas A. Christakis (2010). Correlated genotypes in friendship networks PNAS DOI: 10.1073/pnas.1011687108

Jaime E. Settle, Christopher T. Dawes, Nicholas A. Christakis and James H. Fowler (2010). Friendships Moderate an Association between a Dopamine Gene Variant and Political Ideology The Journal of Politics DOI: 10.1017/S0022381610000617

Peter K Hatemi and Rose McDermott (2012). The Genetics of Politics: Discovery, Challenges and Progress Trends in Genetics DOI: 10.1016/j.tig.2012.07.004

Camperio Ciani A, Cermelli P, Zanzotto G (2008). Sexually Antagonistic Selection in Human Male Homosexuality PLoS ONE DOI: 10.1371/journal.pone.0002282

Ivanka Savic and Per Lindström (2008). PET and MRI show differences in cerebral asymmetry and functional connectivity between homo- and heterosexual subjects PNAS DOI: 10.1073/pnas.0801566105

Roselli CE, Schrunk JM, Stadelman HL, Resko JA, & Stormshak F (2006). The effect of aromatase inhibition on the sexual differentiation of the sheep brain. Endocrine, 29 (3), 501-11 PMID: 16943590

Chen H, Pine DS, Ernst M, Gorodetsky E, Kasen S, Gordon K, Goldman D, & Cohen P (2012). The MAOA gene predicts happiness in women. Progress in neuro-psychopharmacology & biological psychiatry PMID: 22885141

Montag C, Kirsch P, Sauer C, Markett S, & Reuter M (2012). The Role of the CHRNA4 Gene in Internet Addiction: A Case-control Study. Journal of addiction medicine, 6 (3), 191-5 PMID: 22722381

Williams NM, Zaharieva I, Martin A, Langley K, Mantripragada K, Fossdal R, Stefansson H, Stefansson K, Magnusson P, Gudmundsson OO, Gustafsson O, Holmans P, Owen MJ, O’Donovan M, & Thapar A (2010). Rare chromosomal deletions and duplications in attention-deficit hyperactivity disorder: a genome-wide analysis. Lancet, 376 (9750), 1401-8 PMID: 20888040

 
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Publié par le 11 septembre 2012 dans Research, Science

 

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