Polyamory and the Evolution of a Jealous God

Dawkins critiques the myth of monogamy as morality

God the voyeur wants to know what happens in your bedroom.

Image: Adam & Eve by Enrico Baj
In my earlier post, The Origins of Forbidden Love, I highlighted the absurdity of our culture (and dogmatic religions in general) in regards to sexual infidelity. Today, Richard Dawkins has an article in Newsweek that challenges this nearly ubiquitous social “crime” of infidelity. As the good doctor states:

“I want to raise another question that interests me. Why are we so obsessed with monogamous fidelity in the first place?. . . The underlying presumption -- that a human being has some kind of property rights over another human being's body -- is unspoken because it is assumed to be obvious. But with what justification?”

“Even sticking to the higher plane of love, is it so very obvious that you can't love more than one person? We seem to manage it with parental love (parents are reproached if they don't at least pretend to love all their children equally), love of books, of food, of wine (love of Chateau Margaux does not preclude love of a fine Hock, and we don't feel unfaithful to the red when we dally with the white), love of composers, poets, holiday beaches, friends . . . why is erotic love the one exception that everybody instantly acknowledges without even thinking about it? Why can a woman not love two men at the same time, in their different ways? And why should the two – or their wives -- begrudge her this?”

From the perspective of humans as primates, this view is perfectly obvious. Chimpanzees and bonobos (who share around 99% of our DNA) have what’s referred to as a multimale-multifemale mating system. Females have sex with multiple individuals in their troop and make positive choices about which males they’re most interested in. The evolution of sexual jealousy is seen in nascent form in our evolutionary cousins as a sexual partner that is observed mating with another male frequently results in the former male interrupting their l’amour. Males also compete with each other in what biologists refer to as “sperm competition.” Large amounts of ejaculate will be produced in order to “wash out” a previous males' contribution. Chimpanzee and bonobo males are extraordinarily well endowed in the testicle department as a result. A large testicle-to-body size ratio is therefore a strong predictor of a multimale-multifemale mating system.

In contrast to this, gorillas live in a single male-multifemale mating system and the large bodied males have testicles so small that anatomists have reported difficulty in even finding them. This is because there was no selection pressure from the gorilla mating system to produce a large amount of ejaculate (but this doesn’t mean that gorilla females always mate exclusively with their “harem leader,” with predictably jealous tantrums if the alpha male discovers the tryst). Gibbons are monogamous “lesser” apes and likewise have relatively small testes for their body size. In all of these cases the mating system of the primate species in question can be predicted based on male testicle size.

So this leads to the obvious question: are humans more like chimpanzees and bonobos or more like gibbons and gorillas. Unequivocally, (and as you would expect from the genetic evidence) human testicles are more like chimps and bonobos. In fact, in their analysis of the seminal protein genes SEMG1 and SEMG2 (genes that code for semen coagulation or “mating plugs” found exclusively in multimale-multifemale systems) Sarah Kingan and Steve Dorus found a direct correlation between the average number of sexual partners that females of a species will have and the selection for this gene in males. Humans lie closest to chimpanzees and bonobos at both of these loci and this strongly suggests that humans evolved with a multimale-multifemale mating system.

While sexual jealousy is a natural part of such systems, our human predilection is quite extreme and is largely enforced in a completely one-sided, patriarchal form. As I explored in my earlier post, the likely explanation is that religious dogma sought to control female sexuality as if it was the “property” of the male.

“With the power of the state to punish any violation of the law, women were relegated to the status of chattel and their sexual choices were constrained by the threat of capital punishment. It has only been with the rise of secular democracies, and the reduction of religious authority, that women have begun to reclaim their sexual freedom. The last thirty years has seen the largest rise in women’s economic and social power in human history (mostly confined to the West). It’s not coincidental that women have also seen the greatest freedom from sexual coercion and control during this same period.”

While sexual jealousy is unlikely to ever go away, we can take some comfort in the fact that our large brains allow us to recognize the absurdity of our natural reactions and to behave differently if we choose. Far from this being a call to engage in random and frivolous sex, what I (and Dawkins) are suggesting is that monogamy is not the unparalleled moral good that certain well-funded institutions have made it out to be. A committed relationship to a devoted partner is a wonderful experience and, I for one, much prefer it to a life of wanton bachelorhood. By all means be honest and true to your partner (male or female). But also be honest and true to yourself. As a society and as individuals we should understand the diversity of people’s sexual interests and talk about it openly, without clothing our language with a veneer of false piety.

References:

Kingan, S.B., Tatar, M., Rand, D.M. (2003). Reduced polymorphism in the
chimpanzee semen coagulating protein Semenogelin I. Journal of Molecular Evolution 57:159-169. doi: 10.1007/s00239-002-2463-0

Dorus, S., Evans, P.E., Wyckoff, G.J., Choi, S.S., and Lahn, B.T. (2004). Rate of molecular evolution of the seminal protein gene SEMG2 correlates with levels of female promiscuity. Nature Genetics 36: 1326-1329. doi:10.1038/ng1471

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Evolutionary Lap Dance

Study suggests women display sexual cues during estrus

Lap dancers earn larger tips when men sense fertility

In my earlier post, Eye of the Beholder, I pointed to new research showing that women are most attracted to individuals other than their partners while in estrus, the most fertile period of a woman’s menstrual cycle. Their eyes betrayed their attraction to others even under controlled settings. Now it seems that estrus causes men’s eyes to widen as well.

Publishing in the journal Evolution and Human Behavior (pdf), evolutionary psychologists Geoffrey Miller, Joshua Tybur and Brent Jordan collected data on the tips received by lap dancers who were currently taking birth control and those who were naturally cycling. Those dancers who were at their most fertile period received significantly more tips than both dancers on birth control and those at other points in their cycle.

As the authors wrote in their study:

When women and men interact intimately over the course of several minutes through conversation and body contact, women apparently either “signal” or “leak” cues of their fertility status, and these cues influence spending patterns by male consumers. These results argue against the view that human estrus evolved to be lost or hidden from males.

However the study has several limitations, as the authors readily admit. The sample size included only 18 individuals which could result in “false positives,” or finding significant differences where there wouldn’t be in results from a larger population. Secondly, the tip earnings and cycle phase were self-reported by the dancers themselves. Knowing which phase of the cycle you’re in can be difficult to determine (or so I’ve been told) and any mistaken estimates are further compounded when the sample size is so small.

Nonetheless, it would be remarkable if women didn’t show some indications of their reproductive status during their peak of fertility. All female mammals display distinct behavioral and physiological cues during their fertile period that increase their reproductive success as a result. For example many primates, including our closely related chimpanzee and bonobo cousins, will develop large estrus swellings during their fertile period and will be more likely to approach the males they find desirable. Rhesus macaque females will vigorously court males during estrus, even using physical aggression if males reject their advances. Also, lionesses will actively seek out up to 100 matings per day with multiple individuals during their one-week of peak fertility (something that was edited out of The Lion King).

Bonobo sexual swellings coincide with greater sexual interest in males and females

Image: Vanessa Woods
This study doesn’t suggest that the dancers were more attracted to their customers while in estrus (or attracted to them at all), merely that males could detect something irresistibly alluring, more so than during other times, and responded with their wallets.

Our society typically views women’s sexuality as either shameful or reserved for men’s enjoyment (as I’m sure the women in this study know all too well). However, in an ironic twist, this tentative evidence of estrus signaling among lap dancers emphasizes the personal empowerment inherent in the evolution of female sexuality. For thousands of generations those women who displayed a healthy sexual desire during their most fertile period were ultimately more successful in the evolutionary dance. This legacy remains visible today, even in women who want nothing more from the males in their vicinity than a decent tip.

Reference:

Geoffrey Miller, Joshua M. Tybur, Brent D. Jordan (2007). Ovulatory cycle effects on tip earnings by lap dancers: economic evidence for human estrus? Evolution and Human Behavior. doi:10.1016/j.evolhumbehav.2007.06.002

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The Potent Fear of Male Menopause

"Male enhancement" and reproductive senescence


Three products that profit on male insecurities (Enzyte, Viagra and Tiger Penis Wine)

In my earlier post The Evolution of Menopause I discussed how accumulating evidence suggests that reproductive senescence in women is an adaptation promoting inclusive fitness. In response Stew asked the question:

Where does this leave the so-called “male menopause”? . . . Is male menopause a real phenomenon, and if it is what could its benefits be to survival?

I confess that I had never even heard of male menopause before, so this question intrigued me. A quick Google search revealed an onslaught of online “health” sites ready to sell me a host of products to fight this, previously unknown, affliction. These ranged from “new super potent herbal formulations” to “pure potent 200:1 Tongkat Ali Extract” (whatever the hell that is) to the more general “Ultimate Male Potency Booster”. I think I’m noticing a trend in their advertising approach.

Even Harvard Health Publications announces “Is There a Male Menopause: Will Hormones Help?” Apparently we don’t even need to know if there is an actual problem before jumping to an expensive cure. However, after a great deal of discussion about the slow decline of testosterone in men after the age of 40 the good doctors state:

“A 1% yearly drop in testosterone production is imperceptible at first, but by the age of 70, the average man’s testosterone production is 30% below its peak. . . . Despite the obvious appeal of testosterone replacement for older men, most doctors advise against it.”

Their prescription: eat a balanced diet and get more exercise.

So while male menopause seems to have more to do with men’s desire to be 25 forever and less to do with an actual physiological condition (remember, in women menopause is a rapid event that is confined to a specific age window) there is something to this evolutionary question. Why do men undergo a decline in testosterone at all? If evolutionary fitness means leaving the most offspring, wouldn’t the 90-year-old with the enormous Enzyte grin be the ultimate example in "survival of the fittest"?

The answer has to do with life history theory, or evolutionary cost-benefit analyses. Testosterone has numerous behavioral effects, not least of which are risk taking and aggression. Writing in the journal Evolutionary Anthropology, Richard G. Bribiescas shows how among Ache foragers in Paraguay male reproductive value (i.e. what women want) is greatest between the ages of 18 and 30. During this period, Bribiescas euphemistically notes, “males exhibit an acute spike in mortality.”

In other words, males are willing to take excessive risks (or, in rare cases, even take someone out) in order to have a better shot with the ladies. It is during this same period that male testosterone is at its peak. However, it probably wouldn’t be in an individual’s long-term reproductive interests if they continued such behaviors once they were a successful father or grandfather. As it turns out, this is the pattern seen in many other species.

Human male senescence exhibits characteristics that are like those that occur in most mammals. As in other primates, human gamete production is continuous, robust, and relatively invariant with age. However somatic deterioration seems to reflect changes in investment away from reproductive effort to survivorship.

So the evolutionary strategy has been to invest heavily in reproduction during early adulthood and then to focus on yourself and your children in later years. So perhaps testosterone declines over time because in those individuals where it did the end result was having more children with those same genes than in the men who continued to display risky behaviors. While our culture encourages men to be young forever, our evolutionary history suggests this is ultimately a failing strategy.

As for male menopause, there doesn’t appear to be much to it. However, the obsession with male potency has long been a successful marketing ploy. In the Victorian era men would pay to have regular injections of crushed goat testicles and in cultures around the world men imagine that eating the reproductive organs of other animals will somehow provide power to their own. It’s all a load of hooey. But, at least with the “super potent herbs” you might get some of the vitamins that Harvard’s health specialists recommend.

Reference:

Richard G. Bribiescas (2006). On the evolution, life history, and proximate mechanisms of human male reproductive senescence. Evolutionary Anthropology 15(4):132-41. doi: 10.1002/evan.20087

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The Evolution of Menopause

The "Grandmother Hypothesis" is confirmed in a new study


Grandmothers from Gambia are crucial to infant survival.

In my earlier post Life Lessons I discussed the grandmother hypothesis as an explanation for human reproductive senescence, or menopause. A problem arises in understanding why women forgo one-third (and sometimes as much as one-half) of their reproductive lives, a condition unique in the natural world. What selection pressure(s) could result in this unique human adaptation? One cause may have been that, since childbirth is risky in humans, menopause allowed older women to survive longer and better raise their existing children. Another possibility is commonly known as the grandmother hypothesis and argues that women who stopped ovulating in their golden years were freed from the costs of reproduction and were better able to invest in their existing children and grandchildren (thus helping to ensure that more individuals with their menopause inducing genes thrived and had children themselves).

One recurring problem with understanding the evolution of menopause is in how to test it. Unlike fruit flies or bacteria, humans are notoriously slow where reproduction is concerned. Finding a large enough data set to determine which scenario provides the best explanation is therefore difficult. However, in the early edition of Proceedings of the Royal Academy: Biological Sciences (subscription required), Daryl P. Shanley and colleagues utilized a remarkably complete and instructive data set from Gambia. The birth and death records date from 1950 to 1975 and include 5,500 people. Furthermore, since the records predate the existence of a medical clinic they offer a window into a world without the benefits of modern health care. What the data reveal is that children were significantly more likely to survive to adulthood if they had a grandmother’s assistance.

As reviewed in New Scientist:

The data revealed that a child was over 10 times less likely to survive if its mother died before it was 2 years old, but that children between one and two had twice the chance of surviving if their maternal grandmother was still alive. No other relatives had any effect.

Furthermore, by applying a mathematical model to the data to predict the optimum age of menopause (that which would provide women with the most time to assist dependent offspring) the researchers confirmed that menopause should be found just where it currently is.

If the menopause happened later, the population grew more slowly, or even declined. The optimum age for menopause was – as in real life – 50 years.

In our modern world grandmothers may spoil us with presents or candy only on special occasions. But accumulating evidence strongly suggests that grandmothers have been crucial to our very survival for much of human existence. So while women may take a direct fitness hit by reducing the total number of children they can have in their lifetimes, their sum fitness gain (through inclusive fitness) is ultimately higher as the result of menopause. Natural selection offers many strange, seemingly counter-intuitive adaptive strategies such as this (for another example see my post Brooding Angelmakers). However, such empirical explanations reveal the sublime beauty of the evolutionary dance and help us to appreciate the causative factors influencing who we are today.

Do men undergo reproductive senescence? For the answer see my post The Potent Fear of Male Menopause.

Reference:

Daryl P. Shanley, Rebecca Sear, Ruth Mace, Thomas B.L. Kirkwood (2007). Testing evolutionary theories of menopause. Proceedings of the Royal Society: Biological Sciences. 10.1098/rspb.2007.1028

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Thirsty for Love, Or: Beetlemania

File this under "I didn't need to know that."



In a disturbing parallel to human mating practices, female beetles are more likely to mate if the guy offers to buy them a drink. In the current issue of Animal Behaviour (subscription required), Martin Edvardsson has found that female beetles are 40% more likely to mate if they’re thirsty. As reviewed in Science Daily:

Female beetles mate to quench their thirst according to new research by a University of Exeter biologist. The males of some insect species, including certain types of beetles, moths and crickets, produce unusually large ejaculates, which in some cases can account for around 10% of their body weight. The study shows that dehydrated females can accept sexual invitations simply to get hold of the water in the seminal fluid.

So-called “nuptial gifts” are a common tactic by male insects to attract mates. Females of the majority of insects (including the eusocial ants, bees and wasps) mate with multiple males and improve their reproductive success by as much as 70%. As reported in an earlier study in Animal Behaviour (pdf), “the evolutionary maintenance of polyandry in insects can be understood solely in terms of direct effects [i.e. reproductive success].” This has led to sperm competition, a kind of sexual selection, among males in order to improve their chances of fathering some of the eggs. However, in this case we’re witnessing out-of-control sexual selection that puts the peacock’s tail to shame.

Just to put this into perspective (and create a disgusting image that will stick with you all day), 10% of an insect’s body weight would be the human equivalent of filling a 2.4-gallon bucket for your partner’s refreshment.

This isn’t even the most outlandish tale in the annals of insect sexuality. The ejaculate from Drosophila melanogaster (the common fruit fly) is twenty times longer than it’s body length.

Enjoy your lunch!


Drosophila melanogaster after a bit of fun.

Special thanks to Jim for the tip!

References:

Arnqvist, G. & Nilsson, T. (2000). The evolution of polyandry: multiple mating and female fitness in insects. Animal Behaviour 60: 145-164. doi:10.1006/anbe.2000.1446

Edvardsson, M. (2007). Female Callosobruchus maculatus mate when they are thirsty: resource-rich ejaculates as mating effort in a beetle. Animal Behaviour 74(2): 183-188. doi:10.1016/j.anbehav.2006.07.018

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The Origins of Forbidden Love

Sexual equality, double standards and social scale



In my article Eye of the Beholder I described the latest study demonstrating that women tend to be most likely to cheat on their partners in heterosexual relationships when they’re at the most fertile phase of their menstrual cycle.

In response Paul asked the question:

As you point out, these findings are consistent with the well supported notion that women (along with men) evolved more than one reproductive strategy. What puzzles me is why societies are more forgiving of the male who "cheats" than of the female who "cheats" -- a double standard that seems almost ubiquitous?

This double standard has not only been ubiquitous, it has been downright murderous in its application throughout history. However, this is not the case in every society. There is something very specific about which societies consistently demonstrate this double standard and which don’t.

In many indigenous societies sexuality is considered a healthy activity and marriage is a flexible social arrangement that can be initiated or terminated by either sex. For example, among the Vanatinai people of the New Guinea Highlands, Lepowsky (1990:190) writes “sexual activity is regarded as a pleasurable activity appropriate for men and women from adolescence to old age.” Divorce may be initiated by either husband or wife, and is most frequently the result of laziness on the part of the husband or because of the wife’s infidelity. However, infidelity is apparently common enough that Vanatinai marriage rules make any children born to outside fathers the husband’s kin.

This is mirrored among the Australian Aborigines of the Darwin Hinterland. Sansom (1978:100) found that “marriage does not stand for the containment of sexuality within the relationship. It is expected that all husbands and all wives will want lovers.” However, an infidelity that becomes too serious and involves economic favors can frequently lead to bitter argument or divorce.


Yanomami Woman. In many indigenous societies women's sexuality
is not controlled based on male interest.

Even among the Yanomamo, a group regarded as the definitive example of a traditional society in which a man’s dominance status correlates with his reproductive success (high ranking men have multiple wives, low ranking men are bachelors), the picture is not as clear as some would like to believe. Anthropologist John Peters contacted the Shirishana Yanomana during a period when there was a shortage of women and found there were nine polyandrous marriages (one woman with several men) and five monogamous ones (Peters & Hunt 1975).

This flexibility of monogamy and the sexual freedom among many indigenous women today was likely a condition for indigenous groups in the past. As demonstrated by the Montagnais of Northeastern Canada in the 1600s, French Jesuit Paul le Jeune reported with consternation that:

“The inconstancy of marriages and the facility with which they divorce each other, are a great obstacle to the Faith of Jesus Christ. We do not dare baptize the young people because experience teaches us that the custom of abandoning a disagreeable wife or husband has a strong hold on them” (Leacock 1981:50).

Likewise, polygamy (marriage to many partners) was another right that women and men took for granted and which the Jesuits weren’t able to convince the Montagnais to abandon. Perhaps the most telling difference between the sexual standards of indigenous and Western societies came when a Montagnais man objected to le Jeune’s preaching. According to le Jeune:

“I told him that it was not honorable for a woman to love any one else except her husband, and that this evil being among them, he himself was not sure that his son, who was there present, was his son. He replied, 'Thou hast no sense. You French people love only your own children; but we all love all the children of our tribe.'"

The Montagnais of Northeastern Canada demonstrated greater sexual
equality as reported by missionary Paul le Jeune in the 1600s.

In contrast to tribal societies, the rise of states and the development of religious law initiated a starkly different vision for women’s sexual choices. Judaism, Christianity, Islam and Hinduism each share a fundamental concern over the punishment for a woman’s sexual freedom. Whereas any “man that committeth adultery with another man’s wife [both] the adulterer and the adulteress shall be put to death,” (Leviticus 20:10) any unmarried woman who has sexual relations with an unmarried man shall be brought “to the door of her father’s house, and the men of her city shall stone her with stones that she die” (Deuteronomy 22:21).

In fact, the only sexual relationship outside of marriage that does not end in death for the woman is in the case of rape. In that event, if the woman is married, “the man only that lay with her shall die” but, if she is a virgin, “the man that lay with her shall give unto the damsel’s father fifty shekels of silver, and she shall be his wife; because he hath humbled her” (Deuteronomy 22:25-29). The main interest in all of these cases is the paternal interests of kinship and never the interests of the woman in question.


Iranian woman symbolically protests the penalties
imposed by Islamic law for women's sexuality, a
reality common in the history of most religions.

The Bible views women as being half as valuable as men, which is directly comparable to the Qu'ran. There are also direct parallels in punishing women's sexuality. For example, there is no punishment for men in the event of rape except under the categories of "adultery or fornication." In which case “scourge ye each one of them with a hundred stripes. And let not pity for the twain withhold you from obedience to Allah” (Surah 24:2). However, if a married or unmarried woman is “guilty of lewdness,” which Ali (2003:189) defines as adultery or fornication, “confine them to the houses until death take them or until Allah appoint for them a way [flogging for fornication and stoning for adultery]” (Surah 4:15).

The Manu Smriti, the most authoritative books of the Hindu code, or dharma, proscribes that “When a woman, proud of her relations or abilities deceives her husband with another man, then the king should ensure that she be torn apart by dogs in a place much frequented by people.” (Manu VIII:371). Such punishment is necessary because “It is the nature of women to seduce men in this world; for that reason the wise are never unguarded in the company of females” (Manu II:213). The Artharva Veda dictated that if a woman was found guilty of a carnal crime her generative organs were to be cut off and she was ultimately sentenced to death (Arth IV:13).

This stark contrast between indigenous and state societies can be understood as power relationships between the sexes that change as the result of social scale. Anthropologist John Bodley (who I’ve had the pleasure of working with directly) wrote in his groundbreaking work The Power of Scale that:

“The size of human societies and cultures matters because larger societies will naturally have more concentrated social power. Larger societies will be less democratic than smaller societies, and they will have an unequal distribution of risks and rewards” (Bodley 2003:54).

As I touched on in an earlier post (The Evolution of Metapopulations and the Future of Humanity), the invention of agriculture and the subsequent choice by some societies to remain sedentary lead to the unequal accumulation of private goods and the need for a ruling elite to mediate property disputes. This ruling elite frequently identified themselves as an embodiment of the state itself (and often with divine authority). While smaller scale societies would manage any dispute or crime communally, state level societies defined all crimes as crimes against the state (for example, hunting wild deer on the King’s land would be construed as “poaching the King’s deer”).

Males of most species use their larger physical size, or sexual dimorphism, to increase their reproductive success. But females generally have opposing strategies when their reproductive interests are different. Whereas indigenous societies are often more egalitarian, early state level societies codified human sexual dimorphism into law and viewed paternity rights in the same category as property rights because inheritance was of greater concern. With the power of the state to punish any violation of the law, women were relegated to the status of chattel and their sexual choices were constrained by the threat of capital punishment. It has only been with the rise of secular democracies, and the reduction of religious authority, that women have begun to reclaim their sexual freedom. The last thirty years has seen the largest rise in women’s economic and social power in human history (mostly confined to the West). It’s not coincidental that women have also seen the greatest freedom from sexual coercion and control during this same period. There is a great deal of work that needs to be done and, at the same time, there are still strong proponents in favor of moving backwards.


Which culture is more guilty of imposing sexual roles on women?

While greater female sexual equality doesn’t exist in every indigenous society, it would appear that social and environmental factors are crucial. Likewise, as David Schmitt reviewed in his analysis of 48 countries, environmental influences such as the ratio of men to women are strong predictors of sexual dynamics (Schmitt 2005). As Schmitt also reported, most women prefer stable monogamous partnerships. Sexual equality means a woman's right to enter and leave relationships with the same freedom as men. So we shouldn't confuse sexual equality with promiscuity. One could make the argument that, whereas many women in the Middle East and North Africa are subject to one form of patriarchal control and denied sexual equality, women in the West are subject to another form and are made to feel like they must be sexual objects for male gratification.

So, I would argue, the double standard we witness today is actually a cultural holdover from this long tradition of patriarchy. While it may have gotten its start as the result of our evolutionary history (males being larger than females) it has been exaggerated and enforced as the result of male-dominated cultural practices. However, this condition is by no means permanent.


References:

Ali, A.Y. (2003). The Meaning of the Holy Qur’an. Amana Publications, Beltsville, Maryland.

Bodley, J.H. (2003). The Power of Scale: A Global History Approach. M.E. Sharpe. New York.

Leacock, E. (1981). Myths of Male Dominance. New York: Monthly Review Press.

Lepowsky, M. (1990). Gender in an egalitarian society: a case study from the coral sea. In Beyond the Second Sex: New Directions in Anthropology of Gender. Sanday, P.R. & Goodenough, R.G. (eds). University of Pennsylvania Press, Philadelphia.

Peters, J.F. & Hunt, C.L. (1975). Polyandry among the Yanomana Shirishana. Journal of Comparative Family Studies 6:197–207.

Sansom, B. (1978). ‘Sex, age, and social control in mobs of the Darwin hinterland’, in J.S. La Fontaine (ed.), Sex and Age as Principles of Social Differentiation, Academic Press, London.

Schmitt, D. (2005). Sociosexuality from Argentina to Zimbabwe: A 48-nation study of sex, culture, and strategies of human mating. Behavioral and Brain Sciences 28:247-311.

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Bonobos "Red in Tooth and Claw"

Bonobos are not totally peaceful, but reports have been greatly exaggerated

John Hawks has a great review of the commentary following Ian Parker’s New Yorker article "Swingers" on bonobos as well as Frans de Waal’s response in eSkeptic. I’ve previously commented about this issue here and here. However, I disagree somewhat with my fellow anthro blogger that de Waal is accusing Parker of having a political agenda. De Waal points out that conservative pundits picked up on this article in order to, following Parker’s phrase, “use the species as a stick to beat” their ideological drum. What de Waal points out is that Parker was merely “sexing up” his article to raise a little controversy.

Parker presented his trip as a fact-finding mission that had unearthed revolutionary new insights. His message was that bonobos are killer apes, just like their cousins, the chimpanzees. The animal kingdom remained “red in tooth and claw,” as it ought to be.

Yet, the most striking cases of bonobo aggression that he reported have been known for decades, and actually didn’t come from the natural habitat, even less from first-hand observation by our brave explorer.

Challenging a widely held view, even without anything dramatically new to report, is a standard journalistic hook in order to generate audience interest. Whether Parker intentionally chose this tactic or whether it just seemed to be the most exciting way to tell the story isn't all that important. It was a beautifully written piece on the difficulties of fieldwork which ultimately contained flaws about bonobo social behavior.

Parker quotes primatologists Gottfried Hohmann and Craig Stanford (two researchers I greatly respect) in such a way that it implies de Waal has been wrong in his interpretations since he’s never done field work himself. Stanford had some of the most critical statements but, since he’s never done fieldwork with bonobos either, these aren't as relevant as Hohmann's. However, while Hohmann has published some exciting field results showing that bonobo behavior could be more flexible than previously thought, his findings do not contradict de Waal’s interpretations.

For example, Parker takes issue with de Waal's statement that:

“Who could have imagined a close relative of ours in which female alliances intimidate males, sexual behavior is as rich as ours, different groups do not fight but mingle, mothers take on a central role, and the greatest intellectual achievement is not tool use but sensitivity to others?”

Taking each point individually, compare that with the following statements from Hohmann's publications:

1. “Aggression by males against females was rare and was almost never followed by mating between aggressor and target. Female aggression against males occurred frequently but appeared to be independent of mating behaviour.” Behaviour (2002).

2. “Why females of the two Pan species differ in their [genito-genital] displays of social status remains a challenge for future research. The finding that bonobos perform this behaviour so regularly indicates that social status is an important issue for the females of this species. Because of their frequent use, dyadic performance, spatial variability and behavioural plasticity, we suggest that genital contacts can be used to investigate the quality and dynamics of social relationships among female bonobos.” Animal Behavior (2000).

3. “Bonobos show an opportunistic and promiscuous mating behaviour, even with mates from outside the community.” Proceedings: Biological Sciences (1999). Also see Primates (2001) for a short communication involving tolerance of strangers.

4. “The lasting bonds between mothers and sons may be a substitute for male coalitions serving rank acquisition in chimpanzees.” Behaviour (1999).

Other than de Waal's final comment about intellectual achievement (which is a value judgment, even though bonobo empathy has been shown to be greater than chimpanzees) the two researchers don't differ substantially on these points. Parker didn't include this common ground but opted to create a wedge between Hohmann and de Waal. This opened the door for political pundits to declare victory that the bonobo "myth" had been disproved (which shows what standard of evidence they embrace).

However, it's important to point out that new field data has provided more complexity to the social lives of bonobos (and of chimpanzees as well). The excellent book Behavioural Diversity in Chimpanzees and Bonobos (of which Hohmann was a co-editor) shows how different environmental conditions bring out different sides to these species. An in depth review of this book can be found here.

Fortunately, and with all criticism aside, any discussion about bonobos can only aid in the conservation of this critically endangered species as it will activate their strongest base of supporters and bring them to the attention of others who may have never known there was more than one "chimpanzee." I also salute Parker’s dedication for taking such an arduous journey to watch bonobos personally, as brief as that may have been.

However, John Hawks is absolutely correct that Parker's misrepresentations are minor compared to some other blunders in science journalism. It's important for researchers to continually challenge those interpreting scientific results for the public so that such misrepresentations will be minimized.

Currently Gottfried Hohmann and Frances White are conducting field work in the region (I conducted an interview with Dr. White earlier about bonobo behavior). It will be exciting to learn what new insights are discovered about our evolutionary cousins.

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Eye of the Beholder

Psychologists determine that eyes are the window to a woman’s desire.



As a species we are consumed by love. Ask yourself, how many cultural productions (films, stories, songs, dances, arts) do not have love, the loss of love or the absence of love as their central theme? Would you be satisfied with what is left over? Love’s power over us is just one reason why evolutionary research is so fascinating.

A well-worn trope of human culture is men’s obsession with female infidelity. Othello. Madame Bovary. Desperate Housewives. These are just three Western examples of this concern that are paralleled in every society and throughout time. Such powerful and universal human emotions suggest a biological commonality that can be revealed through a scientific lens.

Past research has demonstrated that women alter their sexual preferences based on where they are in their menstrual cycle. Women tend to be much more prone to initiate sexual encounters during their ovulatory period when sex could result in reproduction. Further, in studies based on modern Western societies, women are more likely to fantasize about having sex (as well as make those fantasies reality) with a man other than their current partner during this most fertile phase of their cycle.

Now, a study published online today in Hormones and Behavior demonstrates that this increased sexual proceptivity is apparent simply by looking into a woman’s eyes. Using 14 women (7 on birth control and 7 not) Bruno Laeng and Liv Falkenberg from the Department of Psychology at the University of Tromsø, Norway have shown that women’s pupils dilate more widely to photos of men they were sexually attracted to during their period of greatest fertility.

The researchers had the women look at a computer screen during three different periods of their menstrual cycles to view photos of individuals of sexual significance (their boyfriend or a favorite actor) as well as individuals of unknown sexual significance (their favorite actress, a Norwegian weatherman or an elderly politician). Each time the photos appeared on the screen the women’s pupil size was recorded using an infrared eye-tracking device. The authors determined that:

The findings confirmed the presence of cyclic differences in papillary diameters while watching facial portraits of sexually interesting individuals. Remarkably, the participants using contraceptive pills did not show cyclic fluctuations of pupil sizes.

The results suggest that using birth control flattens the responses by releasing higher levels of progesterone and suppressing estrogens during the fertile period. Also, testosterone, which peaks at midcycle and is directly related to sexual motivation, is suppressed in women on the pill and could negatively influence women’s sexual desire (indeed, reduced libido is one of the common side effects of taking birth control).

Of the subjects not on birth control, the study found that women’s pupils grew largest during their fertile period when viewing pictures of their boyfriend. A close second was the women’s favorite actor.

Assuming that a favorite actor represents the most likely candidate for an extra-pair sexual encounter, an increased response to such a target of interest would be entirely consistent with previous reports that women (at least, in Western societies) report to be more prone to fantasize or have sexual intercourse with a man other than their current partner during the fertile phase of the cycle.

From an evolutionary perspective this is sometimes represented as the selective advantage between dads and cads. During most of their cycle women tend to be most attracted to men who demonstrate good paternal characteristics --- tender, patient, attentive, loyal --- qualities that are often present in individuals with lower levels of testosterone. However, during their peak of ovulation, women on average are more attracted to muscular and/or assertive men who are statistically more likely to make poor long-term partners. Not coincidentally, these are also individuals with higher levels of testosterone.

The arms race between male and female sexual strategy is one of maximizing individual reproductive success. It should come as no surprise that these strategies sometimes differ. For women the strategies are to either choose a partner with phenotypes indicative of high status in order to directly benefit their child or to choose a partner who will assist in child-rearing to ensure that child’s survival. However, as primatologist Sarah Hrdy has suggested with what she terms “Female Plan B,” why not have both? Choose a man who will be a devoted partner and assist in childrearing, but then have a child with a different man who has the genetic qualities promoting high status. If the woman can get away with it, the dad will then help to raise the cad’s bastard (there was a time when that term had serious negative connotations for any children labeled as such).

This has been demonstrated in gibbons, a monogamous “lesser ape” native to Asia and the Indian subcontinent. In a study published in the journal Ethology, 12% of the otherwise monogamous females engaged in extra-pair copulations, or matings with individuals who were not their partners. This is somewhat lower than the current statistics for Western women, of whom 26 to 70 percent engage in extra-pair copulations. The differences aren’t so much important as is the fact that this is a common strategy in females of both species. Females, like males, will use flexible strategies to ensure their reproductive success, regardless of the negative stereotypes our culture places on one rather than the other.

So that flicker of delight you see in your girlfriend’s eyes while watching Ocean’s 13, the slight dilation of her pupils that seems a little bit larger than usual during a certain time of the month, that’s our evolutionary legacy playing itself out today in our living rooms. But don’t panic guys, according to Laeng and Falkenberg’s study women are still mostly interested in the man they’re with. Just make sure you continue to earn that interest.

References:

Laeng, B. and Falkenberg, L. (2007). Women’s pupillary responses to sexually significant others during the hormonal cycle. Hormones and Behavior. doi: 10.1016/j.yhbeh.2007.07.013

Reichard, U. (1995) Extra-pair copulations in a monogamous gibbon (Hylobates lar). Ethology 100(2):99-112

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American Journal of Physical Anthropology, 2007, 132(S34): 137

Lack of inbreeding avoidance and reduction of alliance formation in matrilineally-housed bonobos (Pan paniscus).

E.M. Johnson
Evolutionary Anthropology Graduate Program
Washington State University

ABSTRACT:

Wild bonobo females transfer at sexual maturation into groups without kin. Non-related females perform GG rubbing and grooming to form alliances, and females may mate indiscriminately without risk of incest. The present study investigated social dynamics of a captive bonobo group with a matrilineal core: three adult sisters, their offspring, and an unrelated adult male. It was predicted that these females might demonstrate reduced alliance formation with one another as measured through time spent in proximity and GG rubbing, and that incest might occur because females were housed with their sister's adult sons. 79 hours of 10-minute focal animal samples were collected at San Diego Wild Animal Park in January and June 2006. GG rubbing was absent between sisters, as well as between mother-daughter pairs. Maternal females divided their time equally between their sons (28% of total focal observation time) and their sisters (27%). The largest percentages of total grooming time were between the dominant maternal female and the unrelated male (19%) and between the lower ranking mother and her son (17%), suggesting that alliances were strongest between male-female pairs. Adults sons of two of the sisters formed extended sexual relationships with their own aunts (n1=22, n2=16). Sexual interactions also occurred between males (n=8 bouts), father and daughter (n1=6, n2=4) and brother and sister (n1=12). These findings suggest that matrilineal groupings result in reduced sociosexual interaction between females, and that female bonobos may lack behavioral incest avoidance mechanisms for males other than their own sons.

Full Text (subscription required)

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Looking Haggard

As an atheist I find neither joy nor solace in Ted Haggard's removal from his position as Senior Pastor of New Life Church, the largest Evangelical organization in the United States. On the contrary, I feel sympathy for a man who had a deep sexual attraction to other men but was forbidden from being honest about who he was.

The statement released by Pastor Ted (as he liked his congregation to call him) reveals someone who was tortured for many years by the double life he'd been living. "The fact is," Pastor Ted wrote, "I am guilty of sexual immorality, and I take responsibility for the entire problem. I am a deceiver and a liar. There is a part of my life that is so repulsive and dark that I've been warring against it all of my adult life."

The conflict Pastor Ted must have gone through was undoubtedly intense. The book he lived his life by, the Bible, was decidedly harsh on this subject. Leviticus 20:13 states that "If a man also lie with mankind, as he lieth with a woman, both of them have committed an abomination: they shall surely be put to death."

Pastor Ted believed this heart and soul, and yet he couldn't deny who he was. Of course, a few chapters before this oft-quoted verse (Leviticus 11:10-12), the Bible also states that eating shellfish is an abomination. So either homosexuality isn't as bad as fundamentalists assert, or everyone who's been to Red Lobster is already condemned. But if there's any justice in the humiliation he's now experiencing, it's that for twenty years he publicly condemned homosexuals who were seeking nothing more than to live their lives openly and honestly. For that he should seek forgiveness.

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Defeating Your Inner Rat

If you're like me, then you often feel like an anthropologist on Mars. I observe in confusion as men around me (who apparently share the same sex characteristics I do) behave in ways that would make the war god blush.

I watch as males of our species bluff and strut in what they call friendship. They smack each other around. They downplay one another's achievements while exaggerating their own. They refer to each other using derogatory terms for women's anatomy or as females of the order canine. What a bunch of creeps!

Even worse, I find myself struggling to resist being like them. It's as though I'm in a 1950s werewolf movie or suffering from Tourette's syndrome. I'm desperately trying to keep the monstrous behavior from erupting once again.

As a kid I participated in such masochistic enterprises as hitting your best friend in the arm until he admits pain. When a group of us got together we'd play violent and competitive games like King of the Mountain or Basketbrawl or Monopoly. I would even watch professional wrestling and cheer as two testosterone-poisoned monsters pretended to bash each other's heads in. "Boys will be boys," is the excuse I've usually heard.

This was the conclusion of a paper presented at the American Physiological Society Conference on Oct. 18. The paper, "Sex differences in brain monoamines and aggression," by Jonathan Toot, Gail Dunphy and Daniel Ely of the University of Akron, stated the traditional maxim with some jazzed-up terminology: "Aggression is influenced by a Y-chromosomal effect that decreases amygdala 5HT." In other words, males show more aggression because our Y-chromosome codes for lower amounts of the neurotransmitter serotonin in the part of the brain called the amygdala. When the amygdala is stimulated, serotonin decreases, testosterone increases and aggression results. Simple, right? Forget special child rearing. Get out the pruning shears.

It would appear that Toot, Dunphy and Ely have solved the riddle about why boys are such pains. However, there is another consideration. Their study was done on rats. This isn't as big of a deal as you might think. The evolution of mammals has left us all with the exact same neurotransmitters and pretty similar brain structures. That's why we torture other members of our class in labs around the world to research drugs and behavior. The important consideration is simply this: Rats lack the long period of childhood dependency that humans have.

Humans come out of the oven pretty undercooked. It's at least 12 to 13 years before we're sexually mature, and up to 20 years before we're physically mature. During this period, we rely on adults for food, protection and as models for our behavior. In our current world, these models are extended by the mass media - which overwhelmingly provide entertainment that appeals to our more socially damaging instincts. Hundreds of studies have shown that violent individuals usually come from violent environments. It's reasonable to assume that male aggression in humans is strongly influenced by the environment as well.

What we share with our evolutionary cousin the rat is the innate tendency towards aggression, but biology is not destiny. What you encounter in life, especially early in life, can dramatically affect how you live. Males may have the potential for more aggression, but if it's not emphasized, perhaps it won't be expressed. After all, my father is a very gentle and loving man. Maybe this has something to do with why I'm curious to understand aggression, but don't take part in it anymore (the occasional kung-fu flick notwithstanding).

This is a powerful and world-changing idea, since it's men who presently control most governments on our fragile Earth. Of course, ritual castration of public servants is still a viable option.

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