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The Two Main Ways In Which Evolution Is Not Our Friend

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With millions of years of evolution behind our species, and a billion behind life in general, we might expect – in a Panglossian frame of mind – to function very well, and to be free from unnecessary misery. Wouldn’t the ruthless process of selection have removed causes for fitness-draining suffering and poor well-being in general?

There are two main reasons why we should expect a great deal of unnecessary suffering to be the product of evolution.

1. Adaptation Executors

A maxim of evolutionary biology is that organisms (like us) are adaptation executors, not fitness maximizers. Evolutionary processes create organisms that execute biologically-mediated strategies – it does not create rational beings that maximize fitness in all instances.

In many cases, the detection mechanism is “too sensitive” for our own good – our pain response and our startle response, for example, both generate lots of “false positives” in terms of fitness threats we may respond productively to. This is because in the environment of evolutionary adaptedness, the cost of tons of false positives was outweighed by the benefit of being “right” that one time that counts.

Our social ostracism detection system has also been posited to be hypersensitive, for the above evolutionary reasons. Social belonging has such a high survival value that any potential threat must be addressed immediately. This is true even if it means 100 “false positives” – instances of social ostracism with no actual fitness threat – must be suffered by the individual organism.

What’s a good idea for evolution is not necessarily a good idea for you. Evolution works fine – it just doesn’t give a fuck about the well-being of individual organisms.

2. Failures

In other cases, complex systems interact in such a way that the detection system is “broken.” This may be because the EEA doesn’t match current conditions, as may be the case with asthma, allergies, diabetes, and obesity. In other cases, it may be because organisms aren’t created perfectly every time, and are not perfectly matched even to EEA conditions. Evolution can only act on the mutations it’s given. The pain of a migraine, for instance, is not an indication of a necessary response the way the pain from a burn is. Problems may not reflect any adaptation at all – it might be a defect in the system, or in the organism.

Written in response to this comment by The Plague Doctor.

Written by Sister Y

May 23, 2011 at 2:41 pm

Marriage Is Bad For Your Health

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Marriage modestly increases longevity for some men, but may decrease longevity and other common measures of well-being for women and for most men:

From an interview in The Atlantic with Howard S. Friedman, author of The Longevity Project:

One of our longevity myths is “Get married, and you will live longer.” The data tell a different story.

Marriage was health-promoting primarily for men who were well-suited to marriage and had a good marriage. For the rest, there were all kinds of complications.

For example, women who got divorced often thrived. Even women who were widowed often did exceptionally well. It often seemed as if women who got rid of their troublesome husbands stayed healthy—most women, it seemed, can rely on their friends and other social ties. Men who got and stayed divorced, on the other hand, were at really high risk for premature mortality. It would have been better had they not married at all. [Emphasis mine.]

Consequences like these should be kept in mind when we consider policies that promote marriage as an alleged correlate of good outcomes.

Written by Sister Y

March 14, 2011 at 6:57 pm

Judge Nature

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Now in Spanish! Thanks Daniel.

The extent of the suffering of wild animals is literally unimaginable.

We have a function in our minds for imagining suffering – remembering a dog bite, perhaps, or another nasty injury. And we have an abstract multiplication function in our minds as well. But this doesn’t get us even close to understanding the amount of suffering that occurs in nature in a single minute.

What would it feel like to land on the surface of the sun? Answer: not like anything. You can’t even approach the surface of the sun; even millions of miles out, shielded by a spacecraft, a human body would disintegrate. We are physically incapable of perceiving how bad the surface of the sun would feel.

Thus it is with the amount of suffering in the natural world (and, incidentally, its subset, the human world).

1. On The Ways In Which Nature Makes Andrea Yates Look Like June Cleaver

This photograph shows a Eurasian coot feeding its chick:

These coots may hatch up to nine chicks (so we learn from David Attenborough). But under normal circumstances, food is in short supply. The parent birds feed the baby birds on tiny shrimp for the first three days after hatching. Then, mama coot turns into Mommy Dearest. A baby bird begs for food, as usual – but, with no warning, the parents “punish” it, biting the chick hard on its tiny head. The parents do this to all the chicks in turn. Eventually, one chick is singled out for special torture, and abused until it stops begging for food and starves to death.

This process is repeated until only two or three chicks survive.

Pelicans hatch three chicks, but under normal circumstances, only one survives. Instead of the parent birds doling out death, it’s the siblings – the two larger birds pluck at the smallest with their sharp beaks and knock it out of the nest. Then the conspirators turn on each other until only one chick is left.

Is that awful?

Is that tragic?

Is that . . . good?

Sir David himself acknowledges that this might be a bit cruel, by human standards. But, he assures us, it’s all for the best – in especially good years, a pelican or coot can raise an extra chick or two. So torturing baby birds to death serves the purpose of increasing the genetic fitness of the parents by a little bit.

But does that really make it okay?

2. The Incoherence of Species-Relative Morality

We are taught as children not to apply human standards of morality to animal behavior. We do not expect macaques to be egalitarian, nor male lions to refrain from killing cubs sired by other males. We should not, this theory goes, expect animals to raise the babies they produce to adulthood; we should not be dismayed if they, in fact, torture their young to death when it is advantageous for them to do so.

Most people of our era have a strong, visceral inclination against cruelty to animals, just as we do against cruelty to human children. We judge animal suffering to be bad. Watching the nature special, we hope the impala can evade the lion, but we hope the lion cubs get fed somehow. But watch what your mind does when considering these two contradictory hopes. Does it come to a coherent resolution of the problem? Or does it just shrug its shoulders and spackle the problem over with some bullshit about the circle of life? Life must go on . . . end of thought.

Is it okay that the impala gets eaten? That the cub dies? What about an old lion slowly dying in the hot sun? How about that little chick pictured above, getting abused and starved to death by its parents? Genesis 1:21 (KJV) says: “And God created great whales, and every living creature that moveth, which the waters brought forth abundantly, after their kind, and every winged fowl after his kind: and God saw that it was good.” (Emphasis mine.) According the the Judeo-Christian God, torturing baby coots to death is not just okay, but good. “God” gave us that whopper to swallow; can you swallow it?

Human morality, some may argue, applies only to human actions – not to the actions of animals. I agree with this. For the most part, animals are not agents, but merely robots – machines executing programs created by natural selection. However, morality must certainly also apply to human inaction, and especially our inaction in preventing harm, suffering, and awfulness. What is the moral justification for the “hands off” dogma regarding nature? We often interfere with nature for the good of humans and human industry. Why not for the good of individual animals? Bloody Nature is a machine for pushing genes into the future. Does it really “know best”?

3. Respect for Species?

Nature exists. We try to “conserve” ecosystems in their “natural” state (scare quotes because ecosystems evolve and change over time, in response to environmental pressures, including those from other species). But who is it good for?

Is it good for the animals themselves? Thomas Nagel considers the difficulty of this question in his essay “Birth, Death, and the Meaning of Life,” in his important book The View from Nowhere (from which my blog takes its title). While teaching at Princeton in the 70s, Professor Nagel noticed a sad little spider living in a urinal in the men’s bathroom. The spider appeared to Professor Nagel to have a crappy life, constantly getting peed on; “he didn’t seem to like it,” notes Nagel. He continues:

Gradually our encounters began to oppress me. Of course it might be his natural habitat, but because he was trapped by the smooth porcelain overhang, there was no way for him to get out even if he wanted to, and no way to tell whether he wanted to. . . . So one day toward the end of the term I took a paper towel from the wall dispenser and extended it to him. His legs grasped the end of the towel and I lifted him out and deposited him on the tile floor.

He just sat there, not moving a muscle. I nudged him slightly with the towel, but nothing happened . . . . I left, but when I came back two hours later he hadn’t moved.

The next day I found him in the same place, his legs shriveled in that way characteristic of dead spiders. His corpse stayed there for a week, until they finally swept the floor.

Professor Nagel acted with empathy toward the spider – treating the spider how he imagined the spider would want to be treated. But did he do the spider any good? Would non-interference by Professor Nagel have done the spider any good? The spider might have lived longer, scrambling away from piss streams a hundred times a day, and may have eventually made more spiders. Would that be a good thing?

What do spiders want? Is there such a thing as a meaningful life for a spider? Does a spider’s life do the spider any good?

There is a popular idea, born, I think, from applying the principles of liberalism where they do not belong – the idea that non-interference indicates respect for a species or animal, as if it were a person. (Where interference is allowed, it is to remedy some previous human interference.) This is also (idiotically) applied to human cultural systems, not just biological systems; in this context, it is known as cultural relativism. And it is just as incoherent applied to animals as applied to folks slicing off the clitorises of babies.

Let us for a moment suppose that we will treat individual animals as persons whose pleasures, pains, and desires we can identify and respect. In that case, empirically speaking, non-interference is a shitty policy. We could do more to make animals suffer less by intervention than by complete non-intervention.

On the other hand, perhaps it is the species that is our “person” – we should try to respect a species, or, perhaps, a whole complex ecosystem. But since species and ecosystems are not percipient beings capable of pleasure and suffering, by assigning them respect, we beg the question of the purpose of doing so. Who are ecosystems good for? Or are they perhaps mystically intrinsically good, as Jehovah would have us believe?

4. Is Nature Our Bitch?

To some degree, nature au naturel is good for humans. We need trees and algae and fish in order to live. Genetic diversity, developed over millions of years, ensures the longevity of our biosphere.

We frequently violate our supposed policy of non-intervention with the natural world when doing so benefits humans, in some cases actively seeking the extinction of certain organisms (like smallpox). I don’t think this is wrong at all, because (a) smallpox doesn’t do anyone any good by existing, including itself; and (b) smallpox causes untold suffering. But why draw the line at smallpox? It is my contention that not just smallpox, but all creatures, do not do themselves any good by existing – from spider to coyote to human.

Not only do we breathe oxygen and eat food produced by biological systems; we also appreciate the beauty of complex systems. Can we justify the suffering of baby coots because we think their ecosystem is interesting? Earlier generations of humans liked to torture animals for their own pleasure (and some still do). We now judge this to be evil. But is standing by while animals torture each other in “natural” ways, when we have the power to stop it, any better than actively torturing animals? Responsible people spay or neuter their pets. Why not spay Nature herself?

We don’t even have to harm or kill animals in order to stop Nature from doing her evil deeds. We could simply prevent their reproduction, or even merely cease our current “conservation efforts” that involve breeding animals. Breeding wild animals and releasing them into the wild is doing the ugly work of Genesis all over again – and cruelly claiming that it’s “good.”

5. Is Being Human-Like Better?

We are touched by human-like (or ideal-human-like) characteristics in animals – nurturing young, monogamy, neighborliness, cooperation. Humans, although we commit parental infanticide at a rate higher than any other great ape (as would be expected from our relative immaturity at birth), at least attempt to raise most of our young to adulthood. But is “human” really more “humane”?

Compare the pelicans and coots to the rosella parrot. These parents feed “fairly” – that is, all chicks are fed equally, although they hatch at different times, so some chicks are larger than others. Large, older baby parrots even share their food with their smaller siblings! Aw.

Sound good? Nice parrots. However, they are merely postponing the point at which the red teeth and claws come into the picture. These parrot parents produce more than two offspring. What do you think happens to most of them? They go off and found happy egalitarian parrot families of their own? Maybe for a little while. But a species can’t expand indefinitely. Most of these new parrots will get eaten or starve to death. The lucky few will go on to put dozens of new parrots into the world, for natural selection to claw apart and eat alive. r is evil, but K is not so great either.

Antibiotics were not invented until World War II. Prior to that, any human parent faced the very real possibility of losing some or all of his children before they reached adulthood. Humans were visibly under the same selection pressures as the rest of the animals. However, for a couple of generations, we have managed to pretend that nearly all our offspring can survive to adulthood and bear children of their own. We must look to nature to remind ourselves that this is a temporary fantasy.

If you haven’t read it, please take a look at this short, sweet, and effective piece on Evolution is Suicide: “Why end a life? Why begin a life?

Written by Sister Y

January 4, 2011 at 9:00 pm

Why Can’t Critical Theory Be More . . . Critical?

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Jean-Christophe Lurenbaum, self-described “militant au planning familial” (which I totally want on my business cards), recently published his master’s thesis, entitled Naître est-il dans l’intérêt de l’enfant? (Is birth in the interest of the baby?) at the Université Pierre Mendès France.

M. Lurenbaum makes a very important point: the modern value of preventing suffering is at odds with the ancient value of procreation. We as human beings use various strategies to avoid confronting this conflict, including outright denial of science.

But Lurenbaum is writing critical theory (French feminist critical theory, no less), not science, and he denies science (or makes bullshit assumptions that elide scientific thinking) in his own way. Here is an exemplary claim (p. 25):

Ces indices attestent une création tardive du concept de père, suivie de la mise en place d’un contrôle masculin sur le pouvoir de reproduction des femmes après l’invention de l’élevage : le moment de l’invention de l’élevage focalise donc le soupçon d’une découverte d’un rôle masculin dans la reproduction. [Emphasis in original.]

These observations attest to a relatively late creation of the concept of the father, followed by the development of male control over the reproductive power of women after the invention of agriculture: the moment of invention of agriculture is the moment when mankind first suspects that men have a role in reproduction. [Translation mine.]

Essentially, the claim is that pre-agricultural people did not understand how sexual reproduction works. (Lurenbaum maintains that there are cultures to this day that lack the concept of a father.) This is at odds with the evidence that pre-agricultural peoples do, in fact, understand where babies come from, as evidenced not only directly by ethnographic records, but indirectly by the universality of punishment of female adultery and other means of proprietary control of female sexual capacity by men.

I think that even “true stories” are dangerous, because a “story” is a way of thinking about events (a particularly human, conscious way) that implies that events may be meaningful. “True” “stories” are dangerous because life is actually meaningless, and “stories” make us falsely believe that life is meaningful, and that the actual fact of suffering can be justified by subsequent events, the attitude of the sufferer, etc. But this story of Lurenbaum’s, while deployed toward a noble conclusion, is a false one. I will be the first to admit that humans are stupid monkeys, but even the behavior of literal monkeys reflects the importance of genetic paternity.

Lurenbaum’s entire text is steeped in the myth that, because representations of goddesses are more common in some ancient cultures than representations of male gods, ancient societies must have been literally female-dominated. This is so retarded that it makes the baby Jesus cry, yet it is a core belief of science-denying academic feminist critical theory. It’s just as stupid and falsifiable as a claim of a weeping statue, and it is protected from rational analysis in the way that other culturally important myths are protected.

The idea that the imperative to reproduce is a patriarchal human construction is one that can only be held by a denier of evolutionary biology – or at least someone whose understanding of human evolutionary history is confused.

I will give Lurenbaum props for reminding me that Hitler was an unashamed pronatalist (p. 130). Do you love Hitler? Yes? Then have more babies!

Thanks to Chip for sending me this article, and to Jim for independently posting it at

Written by Sister Y

December 7, 2010 at 6:11 pm

How Babies Destroy Your Fuckability: Female Edition

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Don’t worry.

Your body will still be beautiful after your pregnancy . . . in a way.

Your husband will still find you sexually attractive . . . sort of.

He won’t cheat on you . . . and if he does, it’s not the end of the world.

You’ll be able to lose the weight . . . probably.

The sagging skin isn’t such a big deal.

You brought life into the world – and that makes you beautiful.

You can learn to see beauty in yourself – even if most men don’t.

It will all be worth it in the end.

“You’re not a real woman until people come out of your vagina and step on your dreams.” –Louis CK

Written by Sister Y

July 8, 2010 at 1:01 am

How Babies Destroy Your Fuckability: Male Edition

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Having children makes people less happy.

But more specifically, having a child reduces both a man’s expected frequency of intercourse and quality of his sexual partners. This is true both for a monogamously married man and for a man who does not have an exclusive sexual relationship with the mother of his child. Choosing to reproduce virtually guarantees a worse sex life for a man than he would have had if he had remained childless.

In our society, it is a little disingenuous to speak of a man “choosing” to have a baby. As I have previously discussed, men have zero reproductive rights in our legal system, beyond choosing to avoid sex altogether or to have a vasectomy. However, although the final say is not theirs, men often participate in the decision to procreate. I wish to present an argument from self-interest why men should use what little reproductive power they have to avoid reproducing.

You and Your Baby Mama

The fact that having a child destroys one’s sex life in the context of a marriage is a cultural axiom. In this case, it appears that stand-up comics are, in fact, in touch with empirical reality.

Having a child has disastrous consequences for married couples’ sex lives. 60% of females report decreased frequency of sexual intercourse six months after the birth of her first child than before pregnancy.[1] How much less frequent is intercourse? Half. Frequency of sex eight months after the birth of the first child is about half the (already pretty dismal) pre-pregnancy sexual frequency levels, as reported by both men and women.[2] Eight months after birth, 64% of women and 47% of men reported having sex five times or less per month, compared to (“only”) 29% of women and 15% of men pre-pregnancy. Id. Both men and women were much more likely to rate their sex lives as “not very good” or “poor” compared to pre-pregnancy. Id.

Is the decrease in sexual frequency a byproduct of fatigue? Not really. Levels of fatigue do not significantly predict frequency of intercourse after four months postpartum.[3] Being a great dad who changes diapers will not necessarily get you more sex. Breastfeeding massively reduces sexual frequency[3] – but it’s hardly responsible to avoid breastfeeding in order to have more sex.

Human Mate Selection: Effects of Reproduction

In all the research that has been done on mate selection in humans, two themes[4] recur:

  1. Men care mostly about physical beauty.
  2. Women care most about wealth and earning capacity.

Nature is perverse; having a child, while certainly a fitness-promoting act, comes with serious fitness consequences, most saliently:

  1. A woman’s physical appearance is damaged greatly by pregnancy.
  2. A man’s financial prospects are damaged greatly by having social responsibility for a child.

The most obvious effect of pregnancy on women is postpartum obesity. A Brazilian study found that 35% of each kilogram of weight gained during pregnancy was retained nine months postpartum – even after adjustment for age, pre-pregnancy BMI, body fat at baseline, and years since first parturition.[5] But even women who maintain their weight are affected; every year, thousands of women are rendered clinically unfuckable by pregnancy. Stretch marks, loose skin, horrific changes in body shape, varicose veins, scarring, vaginal muscle weakness, and the incredibly common pelvic floor disorder are all consequences of normal pregnancy.

These are certainly reasons for a woman to avoid pregnancy – but, realistically, a man considering bringing children into a monogamous partnership should be aware of these factors as well. Can you really promise to be faithful – forever! – to a woman who will suddenly become much less attractive, and most likely never really recover? Even if you’re married to Cindy Crawford, pregnancy will take its toll.

Impact on Standard of Living

Most people, of course, do not remain in monogamous partnerships for their entire lives – even those who have promised to do so, and brought children into the world based on that promise. How will your sex life be as a single dad?

First of all, you will have less money. A LOT less money. Methods used to calculate child support vary by state, but expect to pay one quarter to one third of your income – much more if you have sired more than one child. A California man who makes $3000 per month, whose former wife is not employed, will pay $559 for one child – $895 for two children – per month. (Join the fun – calculate your expected child support award in California!)

Not only is your actual earning capacity reduced, but the existence of your child advertises to your potential sex partner that you are less able to provide for her and her hypothetical future children.

It’s not just money, either. Your time and attention are valuable resources, and they are permanently affected by having a child. The above child support calculation assumes a visitation schedule where the visiting parent has the child 20% of the time. In practice, that means half your weekends, and then some. The fact that you have less time, money, and attention makes you a much less attractive potential sex partner to a woman – if you even have time to date.

All this is intended to appeal to self-interest. But being realistic about one’s future prospects helps one make responsible decisions about the future – and that’s not selfish at all. Fewer babies means more sex – and that’s good for everyone.

Your unborn children won’t thank you – but they would if they could.

1. Kumar, R., H.A. Brant, and K.M. Robson. Child-bearing and maternal sexuality; a prospective study of 119 primiparae. J. Psychosom. Res. 1981; 25(5): 373-383.

2. Dixon, M., N. Booth, and R. Powell. Sex and relationships following childbirth: a first report from general practice of 131 couples. British J. General Practice 2000; 50:223-224.

3. De Judicibus, M.A. and M.P. McCabe. Psychological factors and the sexuality of pregnant and postpartum women – Statistical Data Included. Journal of Sex Research, May 2002.

4. See, e.g., Fisman, R., S.S. Iyengar, E. Kamenica, and I. Simonson. Gender differences in mate selection: Evidence from a speed-dating experiment. The Quarterly Journal of Economics, May 2006.

5. Gilberto Kac, Maria H.D.A. Benício, Gustavo Velásquez-Meléndez, Joaquim G. Valente, and Cláudio J. Struchiner. Gestational Weight Gain and Prepregnancy Weight Influence Postpartum Weight Retention in a Cohort of Brazilian Women. J. Nutr. 134:661-666, March 2004.

Written by Sister Y

July 2, 2010 at 8:57 pm

Murder, Suicide, and Murder-Suicide

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The characteristics of murder-suicides differ dramatically from those of simple murders and suicides. What the fuck is going on?

Murders and suicides are individually so common as to rarely merit reporting in the press. Combined murder-suicides are much more rare, but, like simple homicides and suicides, occur with clockwork regularity.

It can be difficult to understand why suicides happen. Is it insanity? Impulse? Crippling despair? If so, why that particular impulse, and why that particular self-destructive despair?

Suicide seems like the most irrational of acts, if not in personal terms than at least in terms of evolutionary fitness. Doesn’t suicide cut off one’s chance to survive and reproduce?

There are, however, reasons to think that the impulse to self-destruction is often one that is conducive to inclusive fitness, or would have been conducive to fitness in recent environments of evolutionary adaptedness.

Murder is somewhat more understandable without doing genetic math. Despite the modern state prohibition on murder and murder’s consequent fitness costs, there is every reason to suspect that most murders are fitness-promoting.[8]

Some murders, however, are not in themselves fitness-promoting, but nevertheless appear to occur as the most extreme effects of a generally fitness-promoting drive. Male violence against women, for instance, seems to be commonly motivated by actual or suspected infidelity, and is of course an effective tool for controlling women and discouraging fitness-damaging adultery. As Johan van der Dennen puts it in his review of David Buss’ The Murderer Next Door: Why the Mind is Designed to Kill,

Traits that have been subjected to natural selection often overshoot and undershoot the exact optimum in terms of their reproductive advantage.[10] [Emphasis mine.]

By far, the most common victims of a murder-suicide are one’s spouse and/or children. Why would anyone commit such a fitness-damaging act? If they are truly inexplicable flukes, why do murder-suicides happen with such regularity? The Violence Policy Center reports that

Medical studies estimate that between 1,000 and 1,500 deaths per year in the United States are the result of murder-suicide. [Violence Policy Center] analysis reveals that, in the first half of 2005, there were 591 murder-suicide deaths, of which 264 were suicides and 327 were homicides. Using these figures, more than 10 murder-suicide events occur in the United States each week.[11]

There are many factors that indicate that the presumed fitness-promoting motives for murder are not present in homicide-suicides. Children killed in murder-suicides are significantly older than children killed in simple filicides.[12] Infants are the most frequent victims of simple filicide, with rates of filicides falling for preschool children and reaching a low point among elementary school children; child victims of murder-suicide, however, are most likely to be elementary school children and least likely to be infants.[9] An infant is much less valuable in fitness terms than an older child; the murder-suicides therefore seem paradoxical.

In addition, biological children are significantly more highly represented among murder-suicide victims than among simple filicide victims.[13] This is especially remarkable, note the authors of one study, because

the familicide victims’ ages averaged substantially older; this age difference should have had an opposing effect since 12-year-olds (the mean age of familicide victims) are much more likely to have had stepfathers than 4-year-olds (the mean age of other filicide victims). [13]

Of course, killing a biological child is likely to be fitness-threatening, whereas killing a stepchild is likely to be fitness-enhancing; again, the murder-suicide data is perplexing in evolutionary terms.

Another data point is the extreme underrepresentation of women among perpetrators of homicide-suicide, as compared to simple homicide and suicide. Women commit suicide at about a quarter the rate of men in the United States, and kill their spouses at about 75% of the rate at which men kill their spouses.[12] But out of 264 murder-suicide perpetrators in the first half of 2005, only 16 were female.[11] (In contrast, of the 327 murder-suicide victims in the same period, 255 victims were female and 72 victims were male.) Females are particularly underrepresented among perpetrators of familicide, a variety of murder-suicide in which a perpetrator kills both a spouse and one or more children. One study of filicide-suicides [9] found that half as many women as men commit filicide-suicide, but that

[s]ixty-five percent of the fathers attempted to kill their wives as well as their children, whereas no mothers attempted to kill their husbands. In all, 55 percent of the fathers, but none of the mothers, attempted familicide, that is, annihilation of the entire family. [Emphasis mine.]

In simple spousal homicides, as noted above, jealousy is the typical motive. But jealousy is rare as a motive in murder-suicides. Bossarte et al. (2006), using data from the National Violent Death Reporting System, found that only 1.9% of murder-suicides during the study period were associated with jealousy.[5] *

Yet another salient difference between murder-suicides and simple homicides is the victim-offender relationship. Homicide-suicides differ from homicides in that a significant majority of homicide-suicides – ranging from 66% to 84% in various studies – involve killings of “intimate partners.” [2] (As noted above, almost all these victims are women.) In contrast, only between 5.2% and 19.2% of simple homicides are wife killings. [7]

The correlation works in both directions. Not only are homicide-suicides more likely to involve intimate partners than simple homicides; intimate partner killers are much more likely to commit suicide than killers of other victims. One study found that only 5% of all homicides were followed by a suicide attempt, but “among men who killed their female intimate partner with a firearm, 59% also took their own life.”[3] Another study found that “among male perpetrators, nearly one third (30.6%) of those who killed their intimate partner (n = 438) also ended their own lives, while only 1.7% of those who killed a non-intimate (n = 3459) also killed themselves.”[5]

The mental state of perpetrators also varies between homicides and homicide-suicides. Homicide-suicide perpetrators are much less likely to be psychopathic than are those who commit simple homicide. A Swedish study reported that

‘Psychopathic’ perpetrators, who generally are over-represented in most violent criminality, were comparatively uncommon. Only seven (4%) in the study group [of 164] met the diagnostic criteria for psychopathy . . . [4]

And homicide-suicides are much more likely than ordinary homicides to be premeditated.[2]

To summarize the differences, homicide-suicides are

  • characterized by older (and therefore more valuable) child victims
  • more likely to include biological (and therefore more valuable) children
  • unlikely to be perpetrated by women (especially murder-suicides that include spousal homicide)
  • unlikely to be motivated by sexual jealousy
  • likely to be wife killings
  • unlikely to be perpetrated by ‘psychopathic’ people
  • likely to be premeditated.

What explains the differences?

One hypothesis is that murder-suicide is motivated by altruism or caring. There is little evidence to support this claim. In one study that reported motive, only seven out of 65 murder-suicides were “mercy killings” – and in six out of seven cases, the victim was over age 55.[5] In addition, a person determined to commit suicide may wish to spare his or her spouse the suffering associated with his or her loss. In fact, men are particularly affected by a spouse’s suicide. The male suicide rate, already high compared to that of women, rises by a factor of 46.2 after the suicide of a partner.[1] (The suicide rate for women, already lower than that of men, rose by a factor of 15.8%.) If altruistically preventing suffering were a major motive in murder-suicides, one would expect women to commit spousal murder-suicide and/or familicide at a rate closer to that of men (or, at least, closer to the rate at which women commit simple suicide or homicide).

Vengeance as a motive is belied by the low rate of jealousy-related homicide-suicides, as noted above, and by the high rate of inclusion of biological children.

I propose a model for homicide-suicide as follows. Homicide-suicide is the result of the unfortunate juxtaposition of two ordinarily fitness-promoting drives. On their own, each drive is evolutionarily adaptive; together, they spell disaster. However, the relatively low rate of murder-suicide indicates that this juxtaposition is rare enough as to not counteract the beneficial selective effects of the two drives individually.

The first drive is the drive to self-destruction under conditions of (a) perceived burdensomeness and (b) failed belonging, as described by Thomas Joiner (though he does not concede that this drive is selective). In selection terms, it is reasonable to commit suicide when the burden one’s continued existence places on one’s genetic kin exceeds one’s prospects for future genetic contribution via creating new offspring (or caring for existing offspring). It is therefore reasonable to conclude that the drive to commit suicide under these conditions would be subject to positive selection. In fact, one study found that perpetrators of homicide-suicide were likely to have experienced “recent legal problems (25.3%) [or] a job or financial problem (9.3%),”[5] both indicating perceived burdensomeness and/or failed belonging.

The second drive is proprietariness. Perceiving one’s children as one’s property is generally fitness-promoting; one protects one’s children from harm, utilizes their labor, benefits from their breeding capacity, and directs their life choices. Proprietariness toward children promotes both the nurturing and protection of children and the parental side of parent-offspring competition.

Proprietariness is the explanation that Daly & Wilson [7] propose to explain the enormous overrepresentation of men as perpetrators of spousal homicide-suicide and familicide-suicide as compared to women. It makes evolutionary sense for a man to be proprietary toward a woman; exclusive sexual access is extremely important for a man in fitness terms. It makes much less sense, evolutionarily, for a woman to be proprietary toward her husband. His sexual dalliances make little fitness difference for her, as long as they do not threaten his continued investment in her children. Purdah and related behaviors are relatively common in societies toward women; nowhere do they exist toward men.

Proprietariness tidily explains the relatively high representation of women among filicide-suicides as compared to familicide-suicides and spousal homicide-suicides; women would be expected to feel proprietary toward their children, but much less so toward their husbands.

Murder-suicide, according to my model, occurs when (a) a perpetrator experiences extreme despair as a result of perceived burdensomeness and/or failed belonging, and therefore wishes to commit suicide; but (b) proprietary feelings toward a spouse and/or children lead the perpetrator to take others with him, as if they were tomb ornaments.


It is probably more psychologically comfortable to assume that men are violent toward women because of suspected infidelity, rather than actual infidelity. However, the violent responses of men, while certainly not morally justified, seem to at least reflect genuine female infidelity most of the time. Daly & Wilson [7] cite a study at p. 201 that found that, in eleven out of eleven non-psychotic spousal homicides studied, “the victim was engaged in an affair with another man or had led the offender to believe that she was being unfaithful to him. In 10 of the cases, the victim made no attempt to conceal her other relationships.” Another study, cited by Daly & Wilson at 208, found that 47% of women who had been raped and beaten by their husbands admitted to adultery, compared to 23% of those who were battered but not raped, and only 10% of women who were not victimized.

*Bossarte et al. (2006) note that their results contradict a 2005 study[14]) on “intimate femicide” using data from the province of Ontario, Canada, from 1974-1994, which found that intimate partner suicide-homicides were significantly more likely to be motivated by jealousy than simple intimate partner homicides (55% versus 42% respectively). The Ontario study also found a higher percentage of de facto unions versus registered marriages in simple murders than in murder-suicides, which contradicts both the Wilson et al. (1995) data[13] and the Banks et al. (2008) data.[2] What do we make of this?

There is circumstantial evidence that makes the Bossarte et al. result more convincing than the Dawson result. First, married people are highly represented among intimate partner murder-suicides compared to unmarried cohabiting couples; unmarried cohabiting couples, on the other hand, are drastically overrepresented among ordinary intimate partner homicides.[2][13] Why does this matter? Daly & Wilson (1988) [7] at p. 213 think that male investment is low in couples living “common law” (compared to married couples). They say: “Perhaps the material investment of men in common-law unions is relatively low, and the women are therefore more likely to be on the lookout for alternatives, inspiring a more coercive proprietariness in their mates.”

Second, a huge proportion of men who kill their estranged wives or wife-equivalents commit suicide. The proportion of men who kill non-estranged adulterous wives are much less likely to also kill themselves (Daly & Wilson (1988) [7] at p. 219). That estrangement is such a trigger fits better with proprietariness than jealousy; losing a female mate, while costly in fitness terms, is nowhere near as costly for the male as potentially supporting non-biological children.

Third, victims of intimate partner murder-suicide are significantly older than victims of simple intimate partner homicide. Barber et al. [3] found a mean age difference of 9.4 years between the two groups. Young wives (who are most valuable and fertile) are extremely highly represented among simple homicide victims; a reasonable interpretation of this is that more valuable women trigger more violent sexual jealousy. Wives who are victims of murder-suicide tend to be older and hence, in evolutionary terms, less valuable (see Daly & Wilson (1988) [7] at p. 206), and so less likely to trigger violent sexual jealousy.

Daly & Wilson [7] (at 219) also dismiss the “remorse” hypothesis (that women rarely commit murder suicide because they lack the highly developed moral sense of men – which assumes that suicides following homicides are committed out of remorse). In fact, murder-suicides often leave evidence of premeditation. In addition, if a murder-suicide is to take place, the suicide generally happens contemporaneously with the homicide; a suicide days or weeks after a homicide, when remorse would be expected to set in, is extremely rare. Daly & Wilson cite a study that found that “whereas 192 homicidal Canadian husbands killed themselves immediately after the homicide, only another 3 committed suicide days or weeks later. Indeed, in the total sample of 6559 Canadian homicides, there were just 8 killers who committed suicide after a delay that might reflect remorseful brooding.”

Works Cited

1. Agerbo, E. “Midlife suicide risk, partner’s psychiatric illness, spouse and child bereavement by suicide or other modes of death: a gender specific study.” J Epidemiol Community Health. 59(5):407–412 (2005).

2. Banks, Laura, Cameron Crandall, David Sklar and Michael Bauer. “A Comparison of Intimate Partner Homicide to Intimate Partner Homicide-Suicide: One Hundred and Twenty-Four New Mexico Cases.Violence Against Women 14:1065 (2008).

3. Barber, Catherine W., Deborah Azrael, David Hemenway, Lenora M. Olson, Carrie Nie, Judy Schaechter and Sabrina Walsh. “Suicides and Suicide Attempts Following Homicide: Victim-Suspect Relationship, Weapon Type, and Presence of Antidepressants.Homicide Studies 2008:12:285.

4. Belfrage, Henrik, and Mikael Rying. “Characteristics of spousal homicide perpetrators: a study of all cases of spousal homicide in Sweden 1990-1999.Criminal Behavior and Mental Health 14:2:121-133 (2006).

5. Bossarte, R M, T R Simon and L Barker. “Homicide-Suicide: Characteristics of homicide followed by suicide incidents in multiple states, 2003–04.Injury Prevention 2006:12(Supplement 2 ):ii33-ii38.

6. Buss, David M. The Dangerous Passion. Bloomsbury, 2000.

7. Daly, Martin, and Margo Wilson. Homicide. New York: Aldine de Gruyter, 1988.

8. ——– Risk-taking, Intrasexual Competition, and Homicide. Nebraska Symposium on Motivation 47: 1-36(2001).

9. Hatters Friedman, Susan, MD, Debra R. Hrouda, MSSA, Carol E. Holden, PhD, Stephen G. Noffsinger, MD and Phillip J. Resnick, MD. “Filicide-Suicide: Common Factors in Parents Who Kill Their Children and Themselves.J Am Acad Psychiatry Law 33:4:496-504 (2005).

10. van der Dennen, Johan M. G. “Review Essay: The Murderer Next Door: Why the Mind is Designed to Kill.Homicide Studies 2006:10:320.

11. Violence Policy Center. “American Roulette: Murder-Suicide in the United States.” (2006).

12. Wilson, M. I. & Daly, M. “Who kills whom in spouse killings? On the exceptional sex ratio of spousal homicides in the United States.Criminology 30:189-215 (1992).

13. Wilson, Margo, Martin Daly, and Antonietta Daniele. “Familicide: The Killing of Spouse and Children.Aggressive Behavior 21:275-291 (1995).

14. Dawson, Myrna. “Intimate Femicide Followed by Suicide: Examining the Role of Premeditation.Suicide and Life-Threatening Behavior 35(1) (2005).

Written by Sister Y

April 3, 2009 at 7:28 am