Yearly Archives: 2010

Evolution and Inequality

I get emails from creationists occasionally, mostly good-natured ones rather than hate mail, but always disputatious in nature (of course). Recently I engaged in a dialogue with a family friend who is a creationist of the “your faith in science is no different than my faith in god” variety, and part of our disagreement came around to the question of whether the world is getting better or worse for people. This question isn’t central to whether or not evolution is true, but it may have a key role to play in the question of whether knowledge of evolution is useful.

As evidence for moral improvement, I cited Steven Pinker’s research on declining violence in The Better Angels of our Nature and in defence of moral regression my friend cited rising divorce rates and increasing narcissism, individualism, instant gratification, and the “subtle violence” that leads to “relationship breakdown.” As evidence for his view, he sent me a New York Times article entitled “Is The World More Depressed?”

So is the world more depressed? And if so what does that have to do with evolution? Here’s my response to my creationist friend in the form of a blog post.

The first thought that comes to mind is a question: once you’ve dismissed science as “a large, constantly shifting field of all kinds of contradictory theories,” how can you then go on to quote scientific studies in defence of your view that the world is getting worse? It seems to me you must either accept the findings of science as a by-and-large reliable guide to what is true and real (including the scientific evidence for evolution), in which case you must critique the findings of science using the tools of science when you think it has gone astray, or else you must cease and desist all reference to its findings. Any attempt to have it both ways, dismissing science in general while also citing it in defence of your views, strikes me as deeply hypocritical.

Moving on, I have another observation: the New York Times article you sent me attributes rises in stress and mental illness and depression to “Our awareness of other people and where we stand in social space” and points out that “We know that social position affects both when you die and how sick you get.” Note that the important thing here is social position, which means relative position. In other words, it doesn’t matter how much you have, what matters is how much you have compared to others around you. When the article states with confidence “we know that…” the writer is talking about knowledge based on scientific evidence, and here’s an excellent video that sums up the research admirably.

Now ask yourself: why would this be? What part of god’s plan would explain the fact that relative differences in wealth and resources are so much more important than absolute differences in wealth and resources? Does this interesting fact about human nature have anything whatsoever to do with Adam and Eve, or Moses, or Jesus? Is it predicted by the bible you believe in?

My point is this: the details only makes sense in light of our evolutionary history. The observed pattern is just as true of baboons as it is of humans. In primates, greater inequality in social status usually means greater inequality in survival and reproduction rates, which is why our stress hormones have evolved to be consistently sensitive to changes in rank. We are the descendants of primates who followed those hormonal triggers to evolutionary success.

What we’re observing is an evolved nature that’s poorly adapted to the modern world, because technology, urbanization, and even agriculture are relatively modern developments, and genetic evolution can’t keep up with cultural change. In some ways this is good, because cultural change has recently made us less racist and less sexist and less violent than the evidence suggests we used to be dozens or hundreds or tens of thousands of years ago. Culture can make us better people than we apparently evolved to be.

But the benefits of cultural change are not cost-free. Thanks to technology and media we have more people to compare ourselves to, more people to compete with, and more people to feel inferior to, and this constantly triggers stress hormones that harm our physical and mental health, just like it does in baboons only with greater intensity. So culture can also make us physically and mentally sicker than we evolved to be.

Jonathan Rottenberg’s new book “The Depths: The Evolutionary Origins of the Depression Epidemic” explores these links in much greater detail. I haven’t read it yet, but Maria Popova gives a nice overview in her recent Brainpickings post.

A better scientific understanding of the evolutionary factors at play here will help us to address the problems of depression and social disfunction more systematically and more effectively. I hope we share the common goal of increasing human wellbeing and reducing the amount of misery in the world. If so, science can help us towards that common goal, while the denial of science will only set us backwards.

So what do you think, is evolution worth a second look?

For more on the impact of inequality, I recommend:

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Darwin Day (Video)

A rap tribute to the countless biology teachers in the trenches of science literacy, teaching evolution to millions of students even in the face of religious objections. Nothing in biology makes sense except in the light of evolution, so they deserve our thanks and support.

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Darwin’s America

We’re Making a Movie!

You heard it here first: we’re making a feature documentary about the Rap Guide to Evolution. The film, provisionally titled “Darwin’s America,” will be produced by Creative Chaos Ventures, a New York company whose most recent doc “Casting By” was a film festival favourite and HBO selection. Darwin’s America will follow The Rap Guide to Evolution as we tour the show to the places it’s needed most: the American South and current hotspots of “creationism vs evolution” conflict. Our aim is to engage and entertain, not belittle, and to explore the question: can a performance succeed where traditional arguments and education have failed to make an impact on people’s views about evolution?

The film commences shooting next week with my gig at Mississippi State University for their “Darwin Week” celebrations, followed by a show (for contrast) at the Royal Ontario Museum in Toronto. The rest of the tour stops will be spread through March and April with some additional filming in July, and we are aiming to include gigs in Texas, Alabama, Tennessee, Louisiana, Kentucky and Oklahoma, plus there is still space to add more locations, which is where you come in. If you know of a venue or an organization anywhere in America (red states preferred, but not required) that would like to host a Rap Guide to Evolution performance in March or April, please get in touch. Because of the film and the short lead time I can do the gigs for a fraction of my normal fee.

It’s exciting to be part of a project with a wide open and uncertain outcome, and I’ll keep you posted as the tour and filming process unfolds!

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Verbal Bling, Homicide, and Afrocentricity

When I was commissioned to write The Rap Guide to Evolution and challenged to communicate the key ideas behind Darwin’s theory in hip-hop form, my first thought was to go through my record collection and see if I could find any rap songs that already centre around evolutionary themes. The three that seemed like the best candidates were “I’m A African” by Dead Prez, “Survival of the Fittest” by Mobb Deep, and “Hypnotize” by Biggie Smalls. So I set myself the challenge of re-writing these songs to make them explicitly instead of just implicitly evolutionary.

None of these three songs was written with Darwin in mind (as far as I know), but all three capture important ideas that are taught in biology classes the world over.


I’m A African” by Dead Prez is an expression of black nationalist unity, reminding all black people, whether American, Jamaican, Haitian, etc, that they are children of Africa. As Dead Prez puts it in the outro: “It ain’t ’bout where you stay, it’s ’bout the motherland!” In my remixed version of the song (music video here), I remind all people of all races that they are also children of Africa, although some of us have to trace our ancestry back a bit further to get there. Since all humans lived in Africa (and had dark skin) as recently as 60,000 years ago, our current racial diversity is an evolutionarily recent “skin deep” phenomenon, and the Dead Prez anthem “I’m a African, and I know what’s happenin’!” is a perfect synthesis of that scientific fact, which is increasingly supported by more and more streams of evidence. Also, it’s hilarious when I can get white people, especially older white people (not to mention people of all other races) singing along with the chorus. The more diverse the audience, the more transgressive and cathartic the message. We are all African!


Survival of the Fittest” by Mobb Deep captures the bleakness and danger of inner city ghetto life as well as any song I know. From the opening lines “There’s a war goin’ on outside no man is safe from, you can run but you can’t hide forever…” the song reminds us that the world is sometimes a violent, hostile place, where strength and a hunger to fight for what’s yours are all that keep you from being someone else’s prey. This is also a perfect expression of the classic “nature red in tooth and claw” or “dog eat dog” understanding of Darwinism, in which organisms are locked in a constant and bloody struggle for survival.

The book “Homicide” by Martin Daly and Margot Wilson (summarized in this article) helps to explain how humans fit into this “war of nature” by exploring “the ways in which homicide rates respond to demographic, social and economic variables.” Using an evolutionary psychology model to generate and tests hypotheses about human violence, Daly and Wilson conclude: “Our homicide research indicates that willingness to use dangerous competitive tactics depends in predictable ways on one’s material and social circumstances and life prospects.”

My remix of “Survival of the Fittest” (music video here and live performance here) combines Mobb Deep’s perspective with Daly and Wilson’s, showing how the male coalitional violence and desire to fight for status and dominance articulated so lucidly in the original song are in fact universal (though context-dependent) marks of our species.

Another insight of Daly and Wilson’s is the relationship between life expectancy, income inequality, and age of first reproduction in young women. This suggests an evolutionary link between homicide in men and teen pregnancy in women, both of which can be understood as adaptations triggered by “one’s material and social circumstances and life prospects.” Over millions of years we have evolved the psychological tools needed to deal with certain challenges: scarce resources, dangerous enemies, and significant potential rewards (as well as high potential costs) for strategic youthful risk-taking. The bottom line is: in some contexts men who fail to risk violence and women who delay reproduction are the least likely to contribute genes to the next generation, and that’s when Mobb Deep’s “only the strong survive” perspective ceases to be “senseless violence” and starts looking like an evolutionarily rational response.


“Mr. Brinkman draws parallels between animal kingdom behavior and rap as a survivalist expression of power, pride, menace and sexual magnetism. And as he wryly points out, what is the ostentatious plumage of the male peacock but nature’s bling?” The New York Times

The Notorious BIG’s song “Hypnotize” mixes real, physical bling with incredibly fluid lyricism – verbal bling – creating a harmonious whole with “sexual magnetism” as its explicit raison d’etre. What is the song for? The ladies in the chorus leave no room for doubt, singing: “Biggie Biggie Biggie, can’t you see, somehow your words just hypnotize me, and I just love your flashy ways, I guess that’s why they’re broke and you’re so paid.” According to evolutionary psychologist Geoffrey Miller, this isn’t just what Biggie’s song is for, this is also what “song” – ie the human capacity for music and poetry – is “for” in terms of its ultimate evolutionary function. If this is the case, then Biggie’s words and their hypnotic effect on the female brain are fulfilling their precise Darwinian purpose.

For my remixed version of “Hypnotize” I had to tweak Biggie’s message ever so slightly (lacking any real physical bling of my own to flaunt), by instead putting the emphasis on the verbal bling and its effects.

According to Miller, the ability to synthesize words and music into pleasing arrangements can be understood as a “costly signal” analogous to the peacock’s tail, the nightingale’s song, or the bowerbird’s nest, a talent that was designed by evolution for a single purpose: attracting mates. And what do the ladies get out of the arrangement? They get an unfakeable guarantee of genetic quality, an assurance that the genes behind the display are top notch and will produce healthy and equally sexy offspring, well-equipped to fight diseases (because a disease-susceptible organism couldn’t maintain the necessary brain and body power for the display in the first place) and attract the next generation of choosy groupies.

And what about the female talent for song? Well, human males are choosy too, especially when it comes to long-term investment, fatherhood, and commitment. Singing females may be displaying the same qualities as singing males, that is, well-developed brains and bodies and sexy genes, only their evolutionary goal may be to attract quality instead of quantity. Palaeolithic female pop divas might well have attracted stronger, smarter, higher-status mates than off-key female warblers in the Stone Age. Hey, it seems to have worked pretty well for Beyonce.


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The Rap Up


What a year 2013 was! With your help we completed two crowdfunding campaigns, funding the first-ever three show hip-hop theatre cycle off-Broadway and a music video for the Darwin-inspired peace-anthem “Don’t Sleep With Mean People” (look for the video release in 2014). The Rap Guide to Evolution toured the world, including stops in New Zealand, Germany, Spain, Canada, and all over the USA. We were nominated for an OBA Award for “Best Unique Theatrical Experience” in New York, and the NCSE gave me a “Friend of Darwin Award” for some reason.

2013 was also the year I kicked off a new kind of performance, the “Rap Up,” in which I sit in the audience at a live event, whether a lecture, conference, performance, concert, award show, whatever, with my brain partitioned, part listening and part composing verses on the fly. Then at the end of the event I step to the stage and perform a fresh-minted satirical rap summary, unrevised and unrehearsed, which gets a great response since the content is tailored for the crowd, a transient zen rap that lives only for a single performance (unless it ends up on YouTube). Of course, you won’t catch all the in-jokes unless you were there, but here’s a collection of recent rap up performances that were filmed.

And what does 2014 hold in store? More Evolution touring (Norway, Australia, and the American South coming up this Spring), more rap up gigs, more Canterbury Tales (I’m looking into Edinburgh, fingers crossed), and more new music. I’m working on a solo hip-hop record and have a couple of new shows in development, so stay tuned for releases and announcements coming up.

Happy new year!

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Rap Guide to Evolution in Vancouver

In two and a half weeks I’ll be performing my first-ever public theatre run in my hometown of Vancouver, BC, and the first run of any kind there since the Vancouver Fringe in 2003. My early forays into hip-hop theatre have taken me around the world, but it took a full decade for them to bring me home again! The Rap Guide to Evolution runs from October 29 through November 10 at the Cultch in East Vancouver.


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New Album: Irregular Spirits

Back in 2005 while I was performing at the Brighton Fringe Festival I met and made friends with a network of ridiculously talented UK rappers. Several of them were in a group called The Menagerie, and several others joined the group later on, and over the years I’ve had the pleasure of recording and performing with them around the UK. A few years ago several of us came together to record the album Irregular Spirits, which was just released on CD, vinyl, and digital download from the UK label Tea Sea Records.

 Stream or Download Irregular Spirits Now

In addition to myself, the album features Dizraeli, Elemental, Dr. Syntax, Koaste, Longusto, Vecks, Teej, Jon Clark, Simon Mole, and Sadie Jemmett, with cuts by Nick Maxwell and production by Tom Caruana (of Wu-Tang vs The Beatles fame). The label describes it as “a wildly original album filled with ridiculous flows, soulful ballads, and hilariously twisted hip-hop phantasmagoria worthy of The Island of Dr. Moreau.” I couldn’t have said it better myself.

Watch the video for lead single “Are You Serious?”

Seriously, it’s very difficult to do this album justice with a textual description, so I humbly implore you to just go check it out. It’s a project I’m very proud of, and the artists on it are some of my best friends as well as the rappers I most admire, on the British Isles and worldwide.

If you write a blog or music column, please consider reviewing the record. Here’s the press release.

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Thunderclap With Me!

Screen Shot 2013-08-23 at 5.25.28 PM

This post has one request and one request only: please join my thunderclap!

Link to join:

Thunderclap is a social media amplifier that will blast out a message via Twitter and Facebook from hundreds of different accounts all at once, but only if the owners of those accounts sign up first – that’s you! If I can get 250 people signed up by noon on August 29th, I can finish my current crowdfunding campaign with a mighty bang.

The message I want to send is “Don’t Sleep With Mean People” combined with a quote from the biologist Richard Alexander: “Evolution is most deterministic for those still unaware of it.” That’s one of the main reasons I’m passionate about science communication. By understanding the influence of evolution on our behaviour, we have the ability to resist that influence, and act more in alignment with our goals and priorities.

Please help me spread the message, and get a few of your friends to sign up as well. It’s free, and the power of your added voice would help me immensely.

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Sleep With Whoever You Want, Jeremy Yoder

From a gene’s eye view, is it better to be in the body of a machiavellian psychopath or in the body of a socially-responsible nice guy? The answer to that question depends on the environment, and recent evidence suggests that the answer is far from obvious. My debate with Jeremy Yoder comes down to the question of whether or not conscientious sexual choices can change this equation.

In his third and (thankfully) final post critiquing my “Don’t Sleep With Mean People” campaign, Yoder helpfully narrows his scattershot objections down to a simple and easily refuted point:

My argument isn’t that this genetic contribution [to individual differences in meanness] doesn’t exist—it’s that this genetic contribution is pretty much meaningless from the perspective of an individual person’s dating life.

I should note that this is Yoder’s argument now. In his previous post it was about how “natural selection needs genetic variation in order to operate” and Yoder was (or acted like he was) skeptical that differences in meanness are due in any part to genetic variation. Now he acknowledges the evidence that genetic variation does in fact play a role in determining human temperaments, but claims this is irrelevant to selection because our genes are sensitive to environmental triggers:

If genetic variation is only strongly predictive of variation in criminality for people who’ve experienced many environmental risk factors, then you’d have to exclusively date people with those risk factors (this is a filter I haven’t found on OKCupid yet) in order to know that the variation in their personalities is probably due to genetics.


Let’s take a moment to note that my campaign is not titled “Don’t Sleep With Genetically Mean People.” The concept is specifically agnostic about the relative contributions of environment and genes – it doesn’t matter! As I’ve said from the beginning, I’m assuming only that some component in some people is genetic. As long as that’s true, targeting meanness in general will impact both genetically and environmentally caused meanness, by incentivizing good behaviour while reducing the relative fitness of mean genes.

“Do something good for your species today. Boycott Dark Triad dudes and stamp out narcissism.” Susan Walsh at

Let’s say a young lady, call her Courtney, were to change her ways and eschew sleeping with bad boys like the guy above. Anytime a prospective lover brags about beating someone up or expresses enthusiasm for street racing or firearms she breaks things off with him. She doesn’t know (or care) which of these guys were exposed to risk factors and which weren’t, which of them have mean genes and which are a “product of their environment.” They all get dismissed in turn, and she ends up settling down with a conscientious, supportive, responsible guy. What’s the worst that could happen? Here’s Yoder’s doom-and-gloom scenario:

You could end up reproducing with someone whose genome is chock-full of variants for “meanness” that are never apparent in the right environment.

In other words, the guy is a prince among men and never mistreats her or anyone else, but he carries latent genes for meanness. So what? She gets a great guy and has a happy life! Genes for aggression that don’t get expressed can’t be targeted by selection (Yoder’s point) but they also don’t increase the rate of spousal abuse or armed robbery (my point). And if those genes manifest themselves as meanness in the next generation due to encountering the requisite environmental triggers, they will be screened out by the next generation of young women who don’t sleep with mean people. Or maybe the carriers will adapt to the new environment (where meanness is suddenly maladaptive), and figure out how to act right. Either way, individuals like Courtney win, humanity wins, and mean people lose (along with Yoder’s argument).

This is not just a cockamamie scheme I cooked up, it’s something that has been happening for tens of thousands of years already. Richard Wrangham and Nicholas Wade have written about the phenomenon of “gracilization” or “self-domestication” in humans and in our close cousins the bonobos. This self-domestication is driven by an evolutionary process in which “the violent and aggressive males somehow had a lesser chance of breeding.” If you agree that a less violent world would be a better one for everyone involved, this transformation is something to celebrate. It is aided by moral philosophy and the rule of law – Geoffrey Miller argues “moral philosophy and political theory have mostly been attempts to shift male human sexual competitiveness from physical violence to the peaceful accumulation of wealth and status.” It is aided by (pop) cultural evolution when peaceable high-status males like Ashton Kutcher inform screaming female fans that sexiness consists of being “intelligent, thoughtful, and generous.” And I hope it is aided, in some small way, by my campaign.

When Jeremy Yoder first started sniping at me I thought he was just being an annoying pedant, but I’ve been flabbergasted to discover that he truly believes mate choice makes no difference to human behaviour, and individual sexual choices could not, under any circumstances, make future generations perceptibly, genetically nicer. How on earth could a practicing biologist adhere so tenaciously to this position? Does he really think male-on-male aggression is sexually selected in every mammal species except ours? Yoder is clearly not a blank-slatist, so in the end I can only return to my original “ad homo-nem” diagnosis (with apologies to Jesse Bering). Like the grinch that stole Christmas, Yoder is mad at my “heteronormative” campaign because he feels left out of it as a gay man. His mate choices are very unlikely to influence genes via sexual selection, so he argues that sexual selection “is pretty much meaningless from the perspective of an individual person’s dating life.”

Confidential to JY: if you had just expressed your outrage by saying “I feel hurt and left out” instead of accusing me of peddling pseudo-science, we could have avoided all this ugliness.

My only consolation for Yoder is to point out that we are virtually in the same boat. Because violence is mostly perpetrated by heterosexual males, it’s heterosexual female mate choice that has the greatest chance of changing the evolutionary equation. Peace-loving males like Yoder and I are cheerleaders at best, arguing about the details while female mate choice continues its slow but relentless reshaping of the human genome. I have no delusions that I can change its course, but that doesn’t stop me from wanting to give it a nudge.

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JY’s Five Finger Discount

Sufficient Heritable Variation?

Sufficient Heritable Variation?

In his recent blog post, evolutionary biologist and sleeping-with-mean-people advocate Jeremy Yoder tries his best to win an argument by shoplifting the conclusion rather than paying for it with good points. If you’re just tuning in, our debate was initiated when he bombed my Don’t Sleep With Mean People campaign Pearl Harbour style, prompting me to respond with a challenge: since Yoder claims he is keen to support a project of mine that teaches people about evolution, he should concede that this project is a worthy one and pay up. One thing I didn’t expect to have to do is teach an evolutionary biologist about evolution, but since this one keeps digging himself deeper, here goes.

In his original post, Yoder argued that the DSWMP slogan would never work because it assumes “the major component of variation in meanness is explained by genetics” and because the meanest people he could imagine – Rush Limbaugh, Simon Cowell, and Anne Coulter – would always be rationalized as charming and kind by their lovers. Although I deliberately left the definition of “mean” open-ended (ie “don’t sleep with homophobes” is a fair interpretation), I had less innocuous forms of meanness than social conservatism in mind, things like violence, aggression, cruelty, coercion, etc, the kinds of behaviours that incur felony charges and are overwhelmingly a male-perpetrated phenomenon. In his new post, Yoder’s argument is not that male violence isn’t an adaptation; rather, he argues that our violent tendencies have been so completely drilled into us by natural selection that they show insufficient genetic variation for selection to act on:

It may well be that there is something programmed into the development of human males that makes us, as a group, more likely to be violent once we’ve reached maturity—and, certainly, the development of boys into men is controlled by our genes. But natural selection (or artificial selection promoted by a nerd-rapper) needs genetic variation in order to operate. The fact that every male becomes more violent after puberty doesn’t tell us anything at all about whether individual differences in the magnitude of that change—differences that can be dramatic, both across and within cultural groups—are due to individual genetic differences. And if you don’t know that, you really can’t claim that you could select for reduced masculine meanness.

He’s right that a complete lack of individual genetic differences in proneness-to-violence would be a death-blow for my campaign, but luckily for me and all the other peaceniks who support the DSWMP credo, Yoder simply didn’t bother to look up any of the evidence.

A brief search of “genetics” “heritability” “aggression” and “violence” turns up compelling studies from Applied Genetics and Neuroscience, but the best evidence comes from Behavioural Genetics. Behavioural geneticists have devised excellent methods for estimating the amount of heritable variation in personality and behaviour, and proneness to violence is definitely part of their repertoire. They measure heritability by looking at the differences between pairs of fraternal and identical twins raised together and raised apart, and by looking at the similarities and differences between adopted siblings raised in the same home, thus controlling for environmental vs genetic influences. The New York Times summarizes one research finding (Kevin Beaver’s) like so:

He has tried to measure which circumstances — having delinquent friends, living in a disadvantaged neighborhood — influence whether a predisposition to violence surfaces. After studying twins and siblings, he came up with an astonishing result: In boys not exposed to the risk factors, genetics played no role in any of their violent behavior. The positive environment had prevented the genetic switches… that affect aggression from being turned on. In boys with eight or more risk factors, however, genes explained 80 percent of their violence.

When Yoder falsely criticized me for assuming that “the major component of variation in meanness is explained by genetics” I responded that he was overstating the case: all we need is for the variation to have some genetic basis, even a minor component, and DSWMP would have an effect. Ironically, the evidence suggests that in high risk populations the difference between a violent thug and a good citizen shows 80% heritability! I’m also willing to bet that among the “risk factors” being measured, they didn’t include the presence or absence of conscientious young women promoting the sexual attractiveness of peaceful conflict resolution. “Don’t Sleep With Mean People” is another way of saying: if women take a stand and proclaim that they won’t be turned on by aggression, that could prevent the genetic switches behind aggression from being turned on.

Yoder’s recent argument also contains an interesting analogy that I’d like to expand on. He likens “being a violent male” to “having five fingers on each hand,” with the implication being that it might in fact be entirely environmental conditions that cause any variation from the norm:

Consider another trait that is invariant across human populations: almost everyone on the planet has five fingers on each hand. Five-fingered hands absolutely have a genetic basis… But knowing this doesn’t tell us, when we see a man with only four fingers, that there’s a genetic basis to the variation he represents. Environmental conditions can have profound effects on human skeletal morphology.

As a thought experiment, imagine a hypothetical population of humans where the culturally-favoured method of male-on-male competition is knife fights. Imagine also that knife fights in that population are pretty much the only way a man ever loses fingers, and only the winners are missing fingers, because the losers are all dead (good fighters enjoy a straightforward fitness advantage). Finally, imagine that not all men get into knife fights with equal frequency; some prefer to compete instead with poems or music or by arguing publicly over scientific nuances, and some prefer a combination of strategies. If the tendency to get into knife fights were linked to some stable, heritable personality trait, for instance (dis)agreeableness – and if the heritable variation in that trait were estimated at, say, around 41% or 42% – then having four fingers or less would show significant heritable variation!

Of course, all babies without defects would still be born with five fingers, but the odds of losing one or more fingers after puberty would be strongly influenced by genes. Twin studies would reveal that identical twins were more likely to end up with correlated finger numbers than fraternal twins, and adopted siblings would more closely resemble their biological parents than their adopted parents in number of fingers lost over a lifetime. This is just to point out that Yoder may have his thumb unfairly pressed on the scale in favour of “environmental” factors, which might in some cases be a part of our extended phenotype.

Now imagine some enterprising troubadour, concerned both for the welfare of society (such a pointless waste of fingers!) and for his own welfare as a better wordsmith than a knife fighter, were to write a semi-serious but whimsical song encouraging women not to sleep with men who are missing fingers, which could serve as a proxy for the genes behind the fighting. The women might still be attracted to knife fighters, but also to troubadours and scientists and other types as well, and they might be sick of all the bloodshed. If the song quickly caught on and the women (and gay men) could be heard to sing “He’s no good for kissing, his fingers are missing” on every street corner, knife fighting might disappear from the population, even if the genetic variation remained. Changing the cultural triggers would have the same phenotypic effect as changing the genes. Those low-agreeableness high-aggression low-compassion genes might persist in the gene pool for some time, grudgingly muted by the new culturally-imposed standard of good behaviour, but without their fitness advantage they would eventually be lost to drift.

In the same way, my DSWMP campaign targets the intersection of culture and genes. It also assumes that the effects of genes on human behaviour, and the effects of sexual selection (intentional or otherwise) on gene frequency are probabilistic rather than one-to-one deterministic. If the campaign decreases the likelihood of genes “for” violence (ie genes that increase the probability of violence in certain contexts) being either expressed or passed on at all, I will be satisfied, and if it teaches a few people about evolution in the process, even better.

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