Even though killing someone, or homicide, is perhaps the most perplexing, and yet pervasive, human acts globally, the body of research around why humans perpetrate violence, and resulting theories, seem woefully inadequate. On one hand, the reasoning is readily apparent: violence is complex, and the myriad subsets under killing someone — infanticide, siblicide, parricide, mass murder, serial killers, interpersonal killings, gang and mafia killings, and so on — make it all the more complex to find any sort of unifying theory of why people kill other people. And yet, David Buss in his 2005 book, The Murderer Next Door: Why the Mind Is Designed to Kill, proffers evolutionary psychology as one such unifying theory.
One small, if perhaps pedantic point stemming from my journalism days: As you’ve seen, I’ve referred to killing another person or persons as homicide and will continue to do so. However, throughout the book, Buss refers to it as murder. My problem with that terminology is that murder is a legal term with a legal meaning, and even throughout the book, Buss points to cases that ended up being legally ruled self-defense as murder. That would still qualify as killing someone, but murder? Not quite.
The essence of Buss’ theory is that when you look at generations of humans and the adaptations that evolved over time for Darwinian “survival of the fittest” — that is, characteristics we developed to continue our existence — humans developed killing as an adaptive strategy to continue to survive and ensure our progeny would manifest and continue on, but like other animal species, those who are the potential targets of a homicide also developed adaptive strategies to survive, what Buss calls “antihomicide strategies.” Then the killers get more adept at killing to evade those strategies. We are in a never-ending bout of survival in this yin-yang way. Sure, we obviously made it to a point of having a civilization with a legal structure that prohibits homicide with few exceptions — if we all were just killers, we probably would’ve died out long ago, and of course, some think it’s still possible the end of our species will be us nuking each other out of existence — but as the subheading of the book indicates, Buss’ theory is that the evolutionarily adaptation to see killing as advantageous at times is still within all of us and can be triggered by various contexts, even if thankfully, relatively rarely. Buss has a great line about this, saying, “In an evolutionary since the real mystery is not why killing has been so prevalent over our evolutionarily history, but why killing has not been more prevalent.” The answer goes back to civilization, which has rendered many of the things we evolutionarily adapted to possess and survive, such as the fight or flight response, or in this case, murder, moot. By offering this theory, Buss decidedly rejects other, more common theories of why we commit violence, such as popular media influence on killing, parental practices, and pathological and biological reasonings (mental abnormalities and/or abnormal and/or damaged brain functioning). Across cultures and societies, some of which cannot plausibly be said to have any mass media influence, commit homicidal violence, most people who have whatever we would consider suboptimal parenting never harm someone else (again, homicide is quite relatively rare), and only an exceedingly small number of such killers can be reliably diagnosed as insane and deranged or having some physical condition leading to outlier violence.
Buss touches briefly on the biggest concern the detractors of evolutionary psychology as a theory of violence have: It is an explanation of what is not what ought to be. My philosophy friends might recognize that important distinction. By documenting, as Buss does through various case studies and research, reality as it unfurls before us and unfurled prior, does not mean we condone it or believe it is morally right. That is, even though Buss is saying a select few humans made it to the top of society by seeing homicide as a viable adaptive solution, he is not saying it ought to be a viable adaptive solution. An additional point I would make, is that I believe people’s aversion to evolutionary psychology — especially when Buss makes analogies to other species, and certainly, we are not the only species that kills our own kind — is that we don’t like to think of ourselves, humans, as animals akin to the lion, the chimpanzee, and so on. We are supposed to be a civilized, highly intelligent creature beyond nature, and so, any explanation of why we do things that deviate from civilization, like homicide, must have something to do with what we are doing to ourselves (mass media influence), or that happened to us biologically (malformed brains) rather than like all animals and life on Earth, and we know this to be true of ourselves, being part of the evolutionary process.
I also think Buss makes a radical point that also doesn’t align with what a lot of people believe in that emotions, and more specifically, our passions, are rational. People like to think those who commit a homicide must be irrational, but that goes back to thinking all killers are deranged when it’s the complete opposite, and goes back to Buss’ point of the “murderer next door.” While it may seem difficult for us who couldn’t conceive of killing another person, to Buss, when viewed through an evolutionarily psychology context — these adaptive strategies — they can explain how someone arrives at such a point.
To go deeper, much of these adaptive strategies are in response to mating competition and achieving successful mating to ensure one’s genes carry on. Whether from the anecdotal case studies Buss presents or reasoning through the adaptive strategies from evolutionary psychology, it seems like the vast majority of what motivates people to kill, to consider killing, or to consider themselves potential victims of a killer (Buss presents these cases, too), is related to finding the best mate (or conversely, “losing” them), and if not that, then killings are related to the usual hallmarks of power, envy, and greed. A side point to that bigger discussion Buss presents is that he talks about how men view certain physical characteristics, such as clear complexion and a slim waist, as ideal in a suitable mate because those markers reflect health, i.e., such a mate is capable of healthy reproduction, but didn’t women with bigger hips in the Victorian era signal health owing to them being rich enough to eat well? But perhaps the changing viewpoint on that is more of a cultural thing rather than evolutionary.
This mating competition, along with the secondary issues of pride, status, reputation, greed, envy and thirst for power, can all at once explain why men do most of the killing, are most of the victims of killing, and why so many women are killed by men. To the latter, this mating competition and the resulting danger that it could lead to men (and occasionally, women) viewing homicide as a viable solution, the most dangerous time to be a woman is when separating from a man, even months or years after the fact. Evolutionarily speaking, Buss argues such a separation triggers the brain because now you’re depriving this person of potential progeny, losing that mate to another mating rival, and with the loss of status. Most persons react to it with either only thoughts of killing, or nothing violent at all, but some will see homicide as a solution. I thought that was an interesting aspect of the book, too, with Buss showing the many cases of adults, male and female, not only fantasizing about killing someone, but having a detailed plan of how they would do it, and for the most part, being stopped by the fear of punishment. I can’t say I’ve ever fantasized about killing someone; if anything, because of my periods of depression, I’ve only ever fantasized about offing myself. Again, an aside, but I’m surprised Buss didn’t offer whether he has fantasized about killing anyone since he thinks such fantasizing is normal and common.
Despite this ominous line from Buss, “All men have an evolved psychology of mate killing that lies latent in their brains,” it’s obviously not “activated” in all men because homicide isn’t a common occurrence. But even saying that it’s latent within us is a controversial position for Buss to take, but he provides ample evidence for its soundness. One question that might stem from that ominous Buss line is, shouldn’t we be able to predict who will commit a homicide then? At the very least, we seem to know that if a woman dies, statistically, it’s most likely that her significant other did it (or just generally, the victim’s killer would have been known to the victim), but, as I’ve emphasized a number of times now, predicting a rare event, as homicide is, is still difficult — which is also why I’ve written extensively about how difficult it is to predict and prevent public mass shootings, an even rarer form of homicide.
Since it undergirds his main thesis, Buss spends a great deal of time diving into mating competition, mate poaching (often resulting from killing or motivating the killing) and cuckolding, but I feel like you can’t talk about mate poaching and cuckolding without talking about the KKK, white women, and the treatment of black men in American history. The fear a white man had of being cuckolded by a black man was such a potent force in American history and surely led to many homicides, a.k.a. lynchings. I don’t expect one book to cover everything, but that felt like a big oversight, especially since it would have served to boost Buss’ point!
This isn’t primarily a book about serial killers or mass murderers, because after all, the book is about the murderer next door, but Buss does touch on such cases and believes you can apply evolutionary psychology to such cases as well. Serial killers and mass murderers seek status, another adaptive strategy. In fact, in the years since Buss’ book with more known about public mass shooters, I think you can apply both mating competition and status-seeking to motivations for them. With almost every public mass shooter, we learn there was a recorded instance of domestic violence before the public mass shooting.
Because this is a book about something illegal, and because readers don’t often like to just read about someone’s observations of a problem without a solution, Buss does have a solution to the issue of murder tendencies being latent within us: Since the overwhelming majority of the cases he sites of people having homicidal fantasies say they didn’t carry them out due to fear of punishment, Buss argues we ought to make it more costly to kill — longer sentencing for killing, although obviously, in the American context, some states still have the death penalty, so, I don’t know how you get much higher than that. My problem with that is the United States already over-incarcerates people and compared to much of the Western world, over-sentences people. If anything, a better solution would be solving murders as a deterrent. Buss does touch on how many killings actually go unsolved and killing has lower clearance rates than you might expect. My proposal is that instead of sentencing people we do catch to longer prison terms, what if we solved more of the killings? That could be a deterrent without continuing our carceral ways.
Overall, Buss’s book, even reading it 17 years after the fact, is revolutionary, radical, and I think, right. He is correct that other theories of violence are woefully inadequate, and his proposed theory of evolutionary psychology helps to explain why homicides of all kinds occur. If you go into this book with an open mind, especially on the point that Buss isn’t saying murder as an adaptive solution is how it ought to be, then you’ll be engaging a fascinating, insightful book.