Green Porno and Disgust

Isabella Rossellini is doing a show, Green Porno, in which she performs the mating behavior of a whole range of other species, such as honey bees and spiders. The show is based on a series of videos that she has been making since 2008.

Isabella Rossellini and friend.
Isabella Rossellini and friend.

Holy cow. These are awesome – and biologically accurate, in a whimsical, funny way. Rossellini clearly did her homework. But sexy? Not so much, I think. Rossellini herself says that though the bits are called “Green Porno,” “There is nothing porno about them.”

I teach a course on Sex, Evolution and Behavior, in which I occasionally illustrate key points with short video clips of the mating behavior of other species, from slugs to albatrosses. Not for titillation, mind you, but for education. In fact, while such video clips may be weird, or interesting, or comical, or gross, or some combination of these, they are pretty much never even remotely titillating. At least in my opinion. And my impression is that for most people, sex in other species is generally much more icky than sexy.

Which makes me wonder: why might this be the case?

The world is big, and has many kinds of people in it, and perhaps somewhere on the Internet there are sites for people who really do find the mating behavior of lobsters arousing. But I expect those sites are vastly outnumbered by sites depicting the mating behavior of our own species.

So why do we perceive sex in other species to be disgusting rather than sexy?

One possible explanation is that this disgust response is part of an evolved psychological mechanism that promotes mating decisions that enhance, rather than reduce, fitness. If we found slug sex really sexy, rather than disgusting, we might try mating with slugs, which (among other things) would be a real waste of mating effort.

If this hypothesis is right, that disgust at other species’ sexuality is a reproductive isolating mechanism, an adaptation to keep us from mating with the wrong species, then we should find the sexuality of species closely related to us to be particularly disgusting. After all, we probably couldn’t really mate with a slug even if we wanted to, but mating with something more closely related to us, like a chimpanzee, at least seems within the realm of possibility.

Back when the world had multiple species of humans living at the same time, such as our ancestors and the Neanderthals, interspecies mating would have been a real option. And studies of fossils and ancient DNA indicate that such matings did occur, at least on occasion. Given that hybrids can have various genetic problems, such as infertility, individuals are likely to have more offspring if they reliably mate with their own species, rather than some other species. And indeed, many aspects of animal behavior and anatomy appear to be related to species isolating mechanisms: courtship behavior, species-specific coloration patterns, and genitalia designed to fit like a lock and key, so that the parts only fit with the right partner.

So, what about this prediction, that if disgust is a reproductive isolating mechanism, we should find the sex of species closely related to us to be particularly disgusting? I don’t know of any formal studies of this, but from watching and listening to people’s reactions to monkeys at zoos, I get the strong impression that in general, people really do find monkey sex disgusting, as well as funny and embarrassing.

As a primatologist, I have seen lots of monkey sex: baboons, rhesus monkeys, chimpanzees, gelada monkeys, and so on. All these animals have sex in the open, in public, for everyone to see, so you don’t need to be a creeping pervert to see them going at it. In many cases, you would have to make a real effort to avoid it. And none of it, really, is very sexy, from a human point of view. In chimpanzees, mating is a furtive event that lasts six or seven seconds on average, which often ends with the female screaming and darting away from the male, as if she is terrified that he might beat her up. Which he might well do.

In my first field season as a primatologist, studying baboons in Kenya, I spent quite a bit of time looking at baboon bottoms. Not because I am particularly interested in baboon bottoms, but because (1) if you are following baboons, you’re going to see a lot of baboon bottoms, just that’s what you see when they’re walking in front of you, and (2) baboon bottoms display a whole lot of really valuable information about their reproductive state. You can tell whether a baboon is male or female, for example, just by looking at their bottom, even if they are just little kids. Baboons have a region of bare, tough skin going across their top of their bottoms that serves as a seating pad: the ischial callosities.

Males have a continuous seat pad surrounded by a patch of grey skin:

Back side of a male baboon
Back side of a male baboon









Whereas females have two separate pads, for the left and right cheeks, separated by the genital opening:

Female baboon at Gombe with bright red pregnancy sign.
Female baboon at Gombe with bright red pregnancy sign.







You can tell where a female is in her ovulatory cycle, as when a female is approaching her fertile time, the skin of her perineum swells up into a big pink sexual swelling, which looks extremely uncomfortable. And if a female is pregnant, the bare skin above her ischial callosities turns from grey to bright crimson.

When I was first habituating baboons (following them at a distance so they would get used to us and let us observe them at closer range), one afternoon we managed to get close enough to our group to see them resting on the face of the steep cliff where they would spend the night. Peering through my binoculars, I could see one female with what appeared to be a raw, festering sore by the base of her tail. As the weeks went by and the baboons let us get closer, I realized that this “sore” was just the bloody red pregnancy sign. It doesn’t look nearly so nasty when you are close enough to see that is not in fact a festering sore.

So during my ten months of following baboons around, I spent a lot of time looking at their bottoms, drawing pictures of their bottoms, taking notes of their bottoms to learn who was who and what their reproductive state was. At first, some features of baboon bottoms seemed kind of gross. I got used to that. And eventually I learned what sort of bottoms looked especially appealing to male baboons, by seeing who made special efforts to mate with.

Ahabazi grooming Ubergiji, who has a full sexual swelling.
Ahabazi grooming Ubergiji, who has a full sexual swelling.







But never in my loneliest days in the field did I find baboon bottoms sexy. Sorry babs, that just how it is.

On the other hand, many examples of hybrids exist. For example, as Kate Detwiler has documented, blue monkeys and redtail monkeys at Gombe and several other sites mate and produce hybrid offspring. My first experience studying primates involved a class project looking at the behavior of the hybrid offspring of a sooty mangabey and a mandrill: a mangadrill. So if disgust is part of a reproductive isolation mechanism, it clearly doesn’t always work.

Whether or not disgust is a reproductive isolating mechanism, it certainly plays a big role in regulating sexual behavior. Even within our own species, we perceive many categories of mating behavior as well, kind of gross. Or really gross. Little kids often seem to think that even kissing is pretty gross, much less the other things that grown-ups are rumored to do in private.

And much of the human disgust response makes sense from an evolutionary perspective. For example, various studies have found that women are considerably less interested in graphic depictions of mating than men are. Many men enjoy looking at graphic, impersonal depictions of anatomical function. Many women find that sort of thing disgusting. Instead, they prefer reading romance novels, or watching romantic movies, where sex occurs in the context of relationships developing between realistic characters. Or with vampires. Or werewolves. Whatever.

Is there a reproductive isolation mechanism at work here?
Is there a reproductive isolation mechanism at work here?







The emphasis is on the relationship first, anatomy second.

A recent example of this sex difference in action is the case of the politician Anthony Weiner, who sent pictures of his privates to women who were not his wife. One can imagine him thinking, “Hey, I’d love to have women send me naked pictures of themselves! Surely they would like me to do the same for them!” And maybe there are women who would like that. But I think this response by a blogger is more typical: “The truth is, guys, your ‘junk’ is one of the last things we want to see up close via digital or printed media.”

The Golden Rule, “Do unto others as you would have done unto you,” doesn’t work so well in cases where people have strong differences of opinion about what they would like to have done unto them.

And from an evolutionary perspective, this sex difference makes sense. If it is important to be choosy about mating, then being aroused by random sexual images would be counter-productive. In humans, women tend to be choosier than men. This makes sense, because men and women face much different costs from mating. A man who has sex with a random stranger might get the evolutionary “win” of impregnating her without having to do any work bringing up the baby. A woman who has sex with a random stranger may get stuck doing all the work. Thus for men, sex with strangers is an opportunity, whereas for women it is a risk, and best to be avoided. (Unless, for example, that stranger is so amazing that having his baby would be worth the trouble. Elvis, say, or Magic Johnson.) Disgust at random male junk may thus be an important mechanism guiding mating decisions that prove beneficial, at least on an evolutionary timescale.

Even for men, though, sex with strangers can be risky, if those strangers are infected with nasty diseases. So both sexes should be equally disgusted by anything that indicates such an infection, like festering sores.

In humans and certain other animals, including many bird species, sex often happens within a long-term relationship, rather than with random strangers. And just as in many birds and some mammals, like wolves, male humans do a lot of parental care. If a man has good reason to think his wife is mating only with him, and is uninterested in mating with other men, then he will have good reason to believe that her children are his, and that he should invest in them, by bringing them meat, or carrying them around, or changing their diapers, or whatever.

In contrast, among chimpanzees, males and females both mate promiscuously. Males don’t provide any parental care (apart from defending a group feeding territory), so females are always stuck doing all the work of parenting. However, males sometimes kill babies of females that they haven’t mated with. So females have a strong incentive to mate with all the males of her community, to convince them all that they might be her baby’s daddy.

Given this difference in mating strategies, if female chimpanzees used smart phones, they might like nothing better than to receive photos of male chimpanzee private parts. I suppose that’s an experiment that could be done.

Recently, disgust has gotten lots of attention as one of the key moral emotions. In college, I sat in on J. Z. Smith’s Religion in Western Civilization class.   In talking about Leviticus, the Biblical book of rules, many of which seem baffling beyond belief, Smith argued that “the complaint of the writers of Leviticus was not, ‘God, why have you made me such a sinful being.’ No, it was more like, ‘Why have you made me with so many holes?’” Humans leak all sorts of disgusting substances from their various orifices, and many of the rules of Leviticus involve proper regulation of these fluids.

Smith seemed to think that these rules involved a fairly arbitrary sense of disgust, rooted more in aesthetics than reason. For example, he argued that Jewish dietary law forbade eating pork because pigs are disgusting animals. They wallow in filth, they eat trash, we shouldn’t incorporate such filthy animals into our bodies. Smith argued that the argument that such laws protected Jews from trichinosis was an invention of 19th century Reform Jews who wanted to find more rational foundations for traditional beliefs.

More recently, Paul Rozin and others have argued that rather than being arbitrary, disgust really is rooted in evolutionary logic: many things that we find disgusting are dangerous: rotting meat, maggots, festering sores, snot, feces and the like can all transmit pathogens. If we eat such things, or even touch them, they can make us sick, or dead. From an evolutionary perspective, it makes sense to have emotional mechanisms that make us avoid such potentially dangerous substances. In this view, feelings of disgust originally based in avoidance of pathogens have expanded to provide one of the main foundations of moral feeling.

A moral emotion like disgust can guide behavior more quickly, and more reliably, than rational arguments. If we had to stop to think and debate amongst ourselves whether rotting carcasses, for example, were safe to touch, we might pick them up and expose ourselves to all sorts of pathogens before we have persuaded ourselves that maybe that’s not such a good idea. The same way with many moral actions: if people think an immediate, gut response of disgust to pedophilia, or rape, or murder, they will be inhibited from even giving it a try.

Disgust seems to involve both learned and innate components, and develops gradually as children mature. Toddlers, for example, seem to find nothing disgusting. But pretty much everyone eventually grows up to find rotting meat and vomit disgusting. People seem to have a natural disposition to develop feelings of disgust towards things that carry a strong risk of infection.

More recently, Jonathan Haidt and others have argued that disgust is at the heart of the six moral foundations or dimensions: care/harm, fairness/cheating, liberty/oppression, loyalty/betrayal, authority/subversion, and sanctity/degradation. In this view, disgust is involved mainly in the sanctity/degradation dimension.

Much of the current political debate about gay marriage involves tension between these different moral foundations. People who emphasize the first three moral dimensions see gay marriage mainly in light of care (we shouldn’t cause emotional harm to people by denouncing their private life choices as sinful), fairness (it’s only fair that people who love each other should be allowed to marry), and liberty (people should be free to be who they are and love who they love). People who emphasize the other dimensions see gay marriage mainly as an issue of authority (scripture says it is wrong) and sanctity (heterosexual marriage is a sacrament; homosexual marriage is wrong). Thus, people on both sides of the debate are morally outraged by the arguments of people on the other side.

And from an evolutionary point of view, an aversion to same-sex mating seems to make a certain amount of sense: such mating doesn’t produce offspring. But it turns out that evolution is more complicated than that. For some species, homosexual mating is not a preference or orientation for a portion of the population; it’s obligatory. For example, New Mexico whiptail lizard reproduces parthenogenetically; the species has only females, and they are all virgins. Nonetheless, even though their eggs are not fertilized, females still have go through the motions of mating, with another female, in order to produce eggs. (Incidentally, this unusual mating system seems to be a result of the hybridization between two other lizard species.)

And even in species that have both males and females, homosexual behavior occurs in a wide range of species. Among Laysan albatrosses in Hawaii, for example, there appears to be a shortage of adult males. Raising a baby albatross takes a huge amount of work. Mom and dad have to take turns flying far away to get fish to feed baby, while the other parent stays with the nest. A single parent just can’t manage. As a result, many females pair with other females. They mate with males who are paired with other females, but nest and raise chicks together with their female life partner.

Rossellini says her Green Porno doesn’t have a political agenda. It is more about educating people about what the world is like for other species. But her videos do an excellent job of illustrating that in nature, sex involves an enormous range of diversity, from the exploding kamikaze penises of honeybees to the playful, anything goes sex of dolphins.

And learning more about the sex lives of other animals is useful for getting a broader perspective for the behavior of our own species, whatever we might personally find to be disgusting. Or not.

Frodo (30 June 1976 – 10 November 2013)

Several of my blog posts have featured Frodo, the iconic alpha male chimpanzee of Gombe National Park. Frodo also figures prominently in several of my research papers, given that he has been a major player in aggression at Gombe, both within his own community, and during attacks on the neighbors. I’m sorry to report that Frodo died on Sunday, 10 November 2013. Perhaps fittingly, given Frodo’s aggressive behavior in life, aggression seems to have contributed to his death. Necropsy revealed that he had a scarred scrotum and infected testis, probably due to what seems to have been a canine puncture wound received in August 2013. As ye sow, so shall ye reap.

Jane Goodall named Frodo for the noble, humble, diminutive hobbit from the Lord of the Rings, which she had been reading to her son. From a cute little baby chimpanzee, Frodo grew to be a hulking brute, a despotic alpha male, and a fearless hunter of monkeys.

Frodo was born on 30 June 1976, the second of Fifi’s nine offspring. Fifi was a highly successful mother and was for many years the highest-ranking female of Gombe’s Kasekela community. As an infant, Frodo proved mischievous, disrupting Jane Goodall’s efforts to record data on mother-infant relationships by grabbing at her notebooks and binoculars. As he grew older, Frodo developed a habit of throwing rocks, charging at, hitting, and knocking over human researchers and tourists. In 1988, Frodo grabbed and pulled at cartoonist Gary Larson’s arm when he visited Gombe, and the next year Frodo severely beat Goodall herself.

In his prime, Frodo weighed 55 kg (121 lbs), larger and stronger than any of his peers. Frodo rose quickly in the ranks as he matured and won the position of alpha male by overthrowing his brother Freud in October, 1997. Frodo reigned as alpha male for 5 years, until weakened by sickness in December 2002. We knew the game was up for Frodo when he gave submissive pant-grunts to the next alpha male, Sheldon, in January 2003.

As alpha male, Frodo ruled by brute force. Unlike his brother Freud, who frequently groomed lower ranking males in apparent efforts to win their support, Frodo rarely groomed any other males, but instead frequently presented himself to be groomed by them.

Frodo competed vigorously for mating opportunities throughout his life, fathering his first offspring, Zeus, when he was 17, and his last, Samwise, when he was 25. He even forced his attention on his own mother, fathering an infant, Fred, who lived for less than a year before dying in a mange epidemic. Frodo fathered both of Gremlin’s twins, Golden and Glitta, the only wild chimpanzee twins known to have survived to adulthood. Frodo’s son Titan follows in his father’s footsteps by throwing rocks at baboons, chimpanzees and people, and has recently challenged the current alpha male. In total, Frodo fathered eight offspring, more than any other male at Gombe but Wilkie (who fathered 10). Frodo’s offspring were born to six different females: Trezia, Patti, Gremlin, his own mother Fifi, Sparrow and her daughter Sandi.

After being deposed in 2003, Frodo spent months by himself recovering, and when he rejoined the other males he had fallen to low rank. He continued to show keen interest in competing for mates and hunting monkeys, but he mellowed considerably, and in his last years rarely showed any signs of aggression towards people.

Frodo was the first chimpanzee that I saw in Gombe, and I recognized him instantly, with his silvery grey back, the round ruff of silvery hair framing his face, and his large size. Frodo taught me what life is like for most chimpanzees: you must constantly be aware of where the alpha male is, because he might charge any time, and may beat you up. The first time he came charging past me, I wondered why everyone was running away; as a kid I had read George Schaller’s descriptions of gorillas, and how when they charged you must stand your ground, and only people who ran got bitten. I assumed the same must be true for chimps. And sure enough, when I studied chimpanzees for my dissertation research in Kibale Forest, Uganda, the alpha male Imoso would simply veer around me if I got in his way, acting as if that was what he meant to do. But not Frodo. He saw that I wasn’t moving and went straight at me, knocking me into the bushes. He beat on me briefly with his fists, but in a surprisingly gentle way. He could have easily done real damange, but he acted as if his only goal was to show me who was boss. Him.

My next day in the forest, I was extremely wary of Frodo. I managed to avoid him for most of the morning. However, during a hunt, someone else ended up with the carcass of a redtail monkey, and Frodo was angry. He charged around, displaying. He charged past a whole line of researchers to get to me, where he knocked me into the bushes yet again.

That was the last time that Frodo bothered me, though. He seemed to accept that I was part of the gang of people that followed him and his community all around the forest, and that I sufficiently acknowledged his magnificence.

Frodo resting on the trail in June, 2009.
Frodo resting on the trail in June, 2009.

Frodo was one of several F-family chimpanzees that rose to high status. Most of Fifi’s offspring that survived to maturity rose to high ranks, with three of them becoming alpha male: Frodo’s older brother Freud, Frodo himself, and the current alpha male, Ferdinand. Fifi’s daughter Flossi is one of the highest ranking females in the Mitumba community. Frodo is survived by four sons (Zeus, Titan, Tarzan, and Sindbad), three daughters (Golden, Glitta, and Samwise), his brothers Freud, Faustino, and Ferdinand, sisters Fanni, Flossi, Flirt at least two grandchildren, and numerous nephews and nieces.

Frodo grooming his daughter Glitter (June 2012).
Frodo grooming his daughter Glitter (June 2012).

Researchers and filmmakers followed Frodo throughout his life, making him one of the most thoroughly documented wild chimpanzees in history. Numerous books and scientific articles described Frodo’s success as a hunter, fighter, and alpha male. Frodo first appeared in films as an infant in People of the Forest: The Chimps of Gombe (1991, Discovery Channel). Frodo knocks presenter Charlotte Uhlenbroeck off her feet in The New Chimpanzees (1995, National Geographic). The films Fifi’s Boys (1996, BBC) and Chimpanzee Diary (1997, BBC) depict Frodo’s rising power and rivalry with Freud. Frodo dominated the giant screen feature Jane Goodall’s Wild Chimpanzees (2002, Imax), filmed at the peak of his powers. More recently, Frodo was featured in The Dark Side of Chimpanzees (2004, BBC), Return to Gombe (2004, Discovery Channel) and Chimpanzee Family Fortunes (BBC, 2006).

Gombe just won’t feel the same with Frodo gone.

La Vie en France

Currently I am on sabbatical in France, hosted in the lab of Michel Raymond at the University of Montpellier-2.

I have been working on papers on chimpanzees and aggression, but also trying to learn French, which has me thinking a lot about language, including the evolution of language, and parallels between biological evolution and linguistic evolution.

I didn’t study French in school, apart from a few weeks in grad school, but over the years have tried, in fits and starts, to learn the language on my own. I have studied two evolutionary cousins of French, Spanish and Italian, which both helps and hurts. There are lots of similarities in the vocabulary and grammar of these languages, but my wife complains that I speak French like a Spaniard.

Languages are like biological species, in that they change over time, and are related to other languages in a tree-like pattern. Just like humans and chimpanzees share a common ancestor that lived around 6 million years ago, French and English share a common Indo-European ancestor that was spoken something like five or six thousand years ago, before the Italic and Germanic branches of Indo-European diverged.
Indo-European Language Evolution







Words are a bit like genes, in that they are units of inheritance. A language is made up of words, much like a genome is made up of genes. Like genes, words change gradually over time, in their meaning and pronunciation. With written languages, we can track these changes with spelling, just as we can track genetic changes with differences in the letters of the genetic alphabet of base pairs (A, T, G and C).

Like our genes, we usually get our language from our parents. But unlike genes, we can also get bits and pieces of language, and even entire languages, from people who are completely unrelated to us.

Unlike animal species (but like some organisms, like bacteria), languages can “mate” freely and exchange words. Thus, English and French have been exchanging words freely over the past thousand years, even though they are from different branches of the Indo-European language family.

One of the fascinating (and sometimes frustrating!) things about French is this long history of interaction with English. After the French-speaking Normans invaded England in 1066, French enjoyed several hundred years as the primary language of the ruling class in England, and English borrowed many thousands of words from French. As a result, written French looks a bit more like English than other Romance languages do; and written English looks rather more like a Romance language than other Germanic languages do. And ever since the Norman invasion, English and French have been trading words back and forth.

Like genes, words accumulate tiny changes over time. Over long periods of time, words with a shared ancestry can drift apart and become very different in spelling, pronunciation, and/or meaning.

Just like in biological evolution, when populations are separated, they gradually begin to accumulate differences and diverge. Just like these changes can lead to the formation of distinct species, they can lead to the formation of distinct languages.

Over time, these repeated branchings from common ancestors lead to tree-like patterns for both languages and species. Historical linguists were the first to appreciate this, for example in this very early depiction of language evolution, which appeared about 60 years before Darwin published an evolutionary tree as the only figure in his Origin of Species.

Tree of Languages by Félix Gallet, c. 1800
Tree of Languages by Félix Gallet, c. 1800


Dawin's Tree
Dawin’s Tree








Just like in biological speciation, the process is gradual and boundaries are often fuzzy. American English is a bit different from British English. French people tell me they need subtitles to understand French movies from Quebec.

Many words are spelled pretty much the same in both French and English, especially anything ending in –tion (nation, séduction, production) or –ism(e) (capitalisme, socialisme). These are often words that were recently invented and borrowed.

Older borrowings, which have had more time to evolve, can look quite different. For example, castle and château both come from the Latin common ancestor, “castellum.” The English word is still pretty similar to the Old North French word “castel,” while in French, the hard “c” has turned to a soft “ch” sound and the “s” has disappeared, signaled only by a sort of fossil of an accent mark, the circumflex (ˆ) on the “a,”  which shows there used to be an “s” there.

French has borrowed lots of words from English, which are sometimes obvious (le sandwich, le weekend, le cocktail) but not always: le foot (football), le pull (pullover, sweater).

Many words that English borrowed from French mean quite different things in modern French. Sometimes this is because the English adopted a quite different meaning of the word from how it is used in French. (An entrée is the entry to a meal in French, just a light little starter course, but for some reason an entrée has come to mean the main dish in English.)

But sometimes this is because the French word has continued to evolve in its own course, or been abandoned altogether for another word.

Like dandelion. English borrowed this from the French phrase, dent-de-lion, “lion’s tooth,” a lovely name that must refer to the toothy looking leaves. But apparently, the French don’t call dandelions “dent-de-lions” anymore. Instead, they call them pissenlit – literally, piss-in-bed, because of the plant’s diuretic properties.

Pissenlits in bloom.
Pissenlits in bloom.

Thanks a lot, evolution.