Is the Human Species Sexually Omnivorous?

The Monolith, Vigeland Sculpture Park

The Vigeland monolith in Oslo (source). 

previously borrowed a phrase from the biologist Robert Sapolsky, who once referred to humans as “tragically confused” in terms of the way we mate. As he put it, we’re not quite a classically monogamous species, but neither are we a winner-take-all polygamous species. Instead, we seem to be a little from column A and a little from column B (and maybe something from columns C and D too). I’ve been trying to think of a way to explain why I think “tragically confused” is an apt description, where some of that confusion originates, and what are some of the potential pitfalls when thinking of human mating patterns. Analogies are imperfect, as some information is always lost in the transfer between concepts, so forgive me if this falls short. And it’s a sports analogy too, but bear with me; I’ll keep it brief.

During the first year I played Little League baseball as a kid, one of the coaches told us that when we played defense we should be ready to field the ball at all times (or at least, be ready to get out of the way or knock the ball down to defend yourself). A hard-hit baseball can really hurt, especially for a young kid who has stopped paying attention because they became distracted by the flock of geese flying overhead (true story). Anyway, he taught us that the best defensive position was to have your glove ready and stand crouched while facing the batter, with our toes pointed slightly inward, or “pigeon-toed.” That may not be textbook coaching, but he explained that by having both feet pointed inward we could quickly pivot and “push off” to our left or right, reacting to where the ball was hit. For whatever reason, I’ve remembered that for more than thirty years. The lesson stuck.

I think “pigeon-toed” is a decent metaphor for much of human behavior, including our sexuality. We are a highly adaptable species, capable of moving in a range of directions by reacting to, and in turn modifying, the world around us. That flexibility is one of our species’ greatest assets – along with other genetic and physiological adaptations – in that it allows us to live on every continent and adjust to a range of social and ecological conditions.

Of course, behavioral flexibility is not unique to humans. The very essence of behavior is that it allows organisms to respond to circumstances, whether it be plants growing towards sunlight or water, anemones swimming away from predators, enormous herds of wildebeest migrating in search of land to graze, or chimpanzees sizing up the complex political situation within their troop.

An anemone escaping a starfish. Flexibility – the ability to respond to circumstances – is the hallmark of behavior, even for anemones. 

This is pretty basic stuff. However, when thinking about sexual behavior, it may help to stop and remind ourselves that evolution did not design organisms to be static things, or genetically determined automatons. One of the potential pitfalls when describing a species’ behavior, particularly for a general audience, is the temptation to use single-word descriptions. For example, among our hominoid relatives, gorillas are said to be polygynous, gibbons are monogamous, and chimpanzees are polygynandrous (or multimale/multifemale). Certainly, behavioral patterns exist, and these are very reasonable assessments of these species’ mating patterns, but one word cannot be all-encompassing.

This matters because, although we like to think categorically, behaviors are complex, variable, and dynamic. Rigid definitions usually mean that some complexity must be shaved off in order to fit into a discrete category more cleanly. The problem is not that the above labels have no merit; it’s that they have a tendency to overshadow the variation that exists within a species. It’s also true that our vocabulary helps shape the way we think about a given species, especially for ourselves.

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A (R)evolution of Tenderness

“Compassion is more important than intellect, in calling forth the love that the work of peace needs, and intuition can often be a far more powerful searchlight than cold reason. We have to think, and think hard, but if we do not have compassion before we even start thinking, then we are quite likely to start fighting over theories. The whole world is divided ideologically, and theologically, right and left, and men are prepared to fight over their ideological differences. Yet the whole human family can be united by compassion. And, as Ciaran (McKeown, co-founder of the Movement of the Peace People in Northern Ireland) said recently in Israel, “compassion recognises human rights automatically; it does not need a charter.”

Betty Williams’ Nobel Peace Prize acceptance speech, Dec 1977



As a college professor, I have some “radical” opinions. For one, I would like to see war and suffering decrease in my lifetime, if not my kids’ lifetimes. I am confident that while war may sometimes be necessary, it does more harm than good, and I am also confident that those negative effects can last for generations. At the same time, I also value truth very much, and I try to avoid naïve interpretations of human biology and behavior. Instead, I try to take a nuanced view when it comes to things like the roots of war, nature/ nurture, and even human sexuality. With all of that said, I’m going to try to splice together a few recent threads to find some reasons for optimism, despite the way current events seem to be going around the world. 

Things are certainly not great. By the end of 2016, an estimated 65.6 million people had been forcibly displaced by conflict, the highest number ever recorded. The UN High Commissioner for Refugees Filippo Grandi lamented that “the world seems to have become unable to make peace.” Partly as a result of conflict, 20 million people are at risk for starvation in four countries: Yemen, South Sudan, Somalia and northeast Nigeria.

The Peace Research Institute in Oslo (PRIO) issued a brief report this month, summarizing the state of global conflicts from 1946 to 2016. In all, the number of conflicts declined from 52 in 2015 to 49 last year, while the total number of battle casualties also fell 14%. This is a tiny bit of good news, although one can see in the figure below that there has been an uptick in all conflicts since 2011, and a long-term increase since the early 1960s. [It is debatable why we should start the clock at 1946, just after the deadliest period of human history, but c’est la vie.] 


By comparison, battle casualties per capita have generally decreased since 1946. While the number of conflicts have gone up, they have been primarily intrastate ones, and smaller in scale. A word of caution, however: “battle casualties” is a metric that looks at violent deaths only. It does not include indirect deaths due to things like broken infrastructure, such as lack of electricity, food/water, and health care that accompany war. If those numbers were included, the number of deaths surely would be higher. And, while the number of conflicts is a tally, battle deaths per capita is a rate, so the two aren’t directly comparable. The total number of deaths might present a different perspective, as might the rate per capita of people who were forcibly displaced.

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Why Mice Don’t Get Ulcers

In his 1994 book “Why Zebras Don’t Get Ulcers,” Robert Sapolsky described the difference between the types of stress that people often experience and the ones that other animal species do. In his titular example, if you were a zebra, you’d most likely face acute physical stress – the lion about to eat you – which requires immediate physiological adaptations (the fight-or-flight response). A second type of stress might be chronic and physical (drought, famine, parasites, etc.).

However, the third type of stress on Sapolsky’s list – the type most prominent in an industrialized human’s life – was social and psychological. While our species certainly benefited from expanding brain size over the last few million years, it too came with trade-offs, including the ability to overthink and worry about things to come down the road. This type of stress would not have featured too prominently into the mental lives of other species. As Sapolsky wrote:

“How many hippos worry about whether Social Security is going to last as long as they will, or what they are going to say on a first date? 

For the vast majority of beasts on this planet, stress is about a short-term crisis, after which it’s either over with or you’re over with. When we sit around and worry about stressful things, we turn on the same physiological responses – but they are potentially a disaster when provoked chronically. A large body of evidence suggests that stress-related disease emerges, predominantly, out of the fact that we so often activate a physiological system that has evolved for responding to acute physical emergencies, but we turn it on for months on end, worrying about mortgages, relationships and promotions” (p. 5 – 6).

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“I’ve never seen a Chinese monkey” (Essentialism & Human Variation)

I taught my first undergraduate anthropology class seventeen years ago, which is sometimes hard for me to believe. In that time, I’ve had over two thousand students enrolled in my courses, many of whom have left an impression on me. I hope I make a good impression on them too, though sometimes I have my doubts. A few years ago, a student asked me what my name was as they started to fill out the line after “Instructor” on the front page of their exam blue book. That was about halfway into the semester. You can’t reach them all, I suppose.

During my fourth year of teaching “Introduction to Biological Anthropology,” we got about two-thirds into the semester, and I paused to take the class’ pulse on how things were going. I asked them if they had any general thoughts about the class, such as what ideas they found interesting (or not), things they wished we could discussed more in depth, etc. I have since forgotten most of the students’ comments, except for one.

I remember that he wasn’t exactly the best student, and that he had struggled with most of the graded assignments. Nonetheless, I still learned something from him that day. He told the class that he thought evolution was an interesting idea, but he was skeptical about it applying to humans because, as he said, “Well, I’ve never seen a Chinese monkey.” This all occurred a long time ago, but I remember that at first I was puzzled by what he meant. And then it clicked.

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Primates and the Day of Atonement

“As far as possible without surrender/  be on good terms with all persons.”

– Max Ehrmann, Desiderata


Our kids were home on Wednesday last week, as our school district observed Yom Kippur, the Day of Atonement in Judaism. I’m not a theologian and can’t claim to have anything beyond a superficial understanding of Yom Kippur, but as we walked past the local synagogue in our neighborhood, surrounded by parked cars, I speculated about how and why such a tradition might have arisen.

From my understanding, Yom Kippur is primarily concerned with seeking forgiveness from God for any transgressions accrued in the last year. However, I was more curious about another related aspect of the holiday, which is that – prior to the day itself – people are also encouraged to seek forgiveness from others they have harmed.

I can see parallels here to my own Roman Catholic childhood and the sacrament of Penance. Of course, as a boy I was just doing what the adults told me to do, going through the motions – perfunctorily confessing to a priest about fighting with my siblings. But I never contemplated why something like Penance might exist, aside from the obvious one of avoiding Hell (that fear seems a lifetime ago).

Most religious traditions and societies probably have concepts like forgiveness, reconciliation, and atonement built into them to some degree. These likely have deep roots, and we can even find some of the basic building blocks of these among other species of primates. Most primate species are highly social, group-living animals, which has a list of pros and cons. The benefits of being social include having more eyes and ears to detect predators, the ‘selfish herd’ idea (less chance for me to be eaten), defense (against conspecifics for territory, against predators), more models of adult behavior (socialization), easier to find mates and food, and (in some species) reaping the benefits of specialized division of labor.  

However, all things in biology have tradeoffs. If you’re going to live in a group, chances are next to nil that there will not be at least some internal conflict. It’s certainly not all-conflict-all-the-time, but the degree of internal conflict depends on circumstances. Two individuals may want similar things most of the time, but they cannot maintain perfectly overlapping interests indefinitely.

Among baboons, social life is rife with conflict as individuals vie for status. In an interview with Robert Sapolsky, he described the impact social stress can have on baboon life, while drawing a comparison to humans:

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Time and Reconciliation: the Christmas Truce

The biologist Robert Sapolsky had a recent essay in The Wall Street Journal on the Christmas Truce of WWI, where he discusses how cooperation might develop under difficult circumstances. I wrote a blogpost on the same topic here a few years ago (in fact, it is still the most viewed thing on this site), and I think we cover much of the same ground. Sapolsky’s essay is better, which I’m fine with; it’s Robert Sapolsky after all.

At the end of the essay, he presents a thought experiment about trying to fast-forward mentally through the passage of time and seeing the present through the eyes of our older, wiser selves. 

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