Blood-Fluke Monogamy

You know how upsetting it is when a celebrity couple to whom you’ve become attached breaks up?  And you know how it’s the worst when they break up because of infidelity?

Then perhaps you can imagine how distressed I was this week when I learned that Schistosoma mansoni, the endoparasitic blood-fluke, wasn’t really monogamous.

Schistosomes are a genus of class Trematoda, or parasitic flatworms.  They are the cause, in humans, schistosomiasis, which kills tens or hundreds of thousands of people every year (depending on whom you ask), and which is the second-most impactful parasitic infection worldwide after malaria.

Unlike other flatworms, schistosomes are dioecious.  During mating, the male, which is much larger, essentially encloses the female in something called, unsexily, a “gynacophoric canal”, where reproduction will occur and where the female will spend the rest of her life.

Or so we thought!  Turns out, blood-fluke couples split up, or, as scientists kind of preposterously put it, “divorce”.  Schistosome divorce was apparently first reported in 2000 by Pica-Mattoccia et al., in the journal Parasitology, but I don’t read Parasitology (although clearly I need to), and so I missed it.

However, my attention fell this week on a 2009 paper by Beltran et al., ‘Adult sex ratio affects divorce rate in the monogamous endoparasite Schistosoma mansoni’.  The authors of this paper found that they could dramatically increase the blood-fluke divorce rate by flooding the bloodstream of infected animals with male schistosomes, thus increasing the number of unpaired, available males.  However, increasing the number of female schistosomes in the bloodstream, i.e. creating a population of unpaired female blood-flukes, had no effect on divorce rates.

There are two possible explanations for this gendered effect.  The first is that the female schistosome is the choosier sex, and so, when there are more available unpaired males from which to choose, some number of paired females will upgrade.  Supporting this view is the observation that there is greater genetic variety among male blood-flukes than among females; this means that a female schistosome may gain a significant advantage from switching mates, while a male probably will not.  For a male schistosome, one female is very like another, and so when you have one, best just to hold on to her; hence the lack of effect on divorce rate when the number of available females was increased.

The other possible explanation is that the free schistosome males act in a predatory manner, and may physically break-up happily joined couples.  Since the male schistosome is much larger than the female, it makes sense that this would only happen when the number of males was increased: the smaller females would be incapable of separating another blood-fluke couple, even if there were more of them.

Of course, these two hypotheses need not be mutually exclusive: as the authors of the study mention in a slightly victim-blaming aside, “the possibility exists that female schistosomes choose not to resist takeover attempts by rival males if they perceive their higher phenotypic and/or genetic value.”

None of this lightens the emotional blow to those of us who had pinned our hopes on blood-fluke monogamy, of course.  It’s over – it was all a lie.  Love is dead.

Image from National Geographic.

Adam Levine and Signaling Theory

Maroon 5 has a new single.  It’s called ‘Maps’ – maybe you’ve heard it?  You’ll know it when you do, because, even though most it of it sounds exactly like all other Maroon 5 songs (not that there’s anything wrong with that), there is one distinctive feature: right after the chorus, Adam Levine (a high singer under normal circumstances), sings, “Following, following, following.”  Or, he doesn’t so much sing it as melodiously squeak it.

I have it on good authority that Adam Levine is very attractive.  I also have an impressive amount of anecdotal evidence that suggests that squeaky voices are not considered desirable in men.  However, in pop music, men often shriek at very high registers in their pursuit of women.  For example, last summer, Jason Derulo subjected us all to the ear-splitting insistence that some poor woman “take him to the other side (toniiiiiiiiight)”.

Munchkin-sounding men are a pop-music staple.  But why?

In evolutionary biology (bear with me here), a ‘signal’ is a trait or behavior which modifies the behavior of the recipient of the signal.  For example, female bower birds are more likely to mate with male bower birds that adorn their nests; nest adornment is therefore a sexual signal.

Signaling is sometimes described as either ‘honest’ or ‘dishonest’.  In the context of sexual selection, an ‘honest’ signal is a signal which accurately predicts the presence of other desirable but invisible traits.  A famous example is the peacock’s tail.  Some evolutionary biologists have argued that the elaborate tail of the male peacock is an honest signal because the tail is metabolically costly, and because the unwieldiness of the tail makes the bird vulnerable to predation, and the male’s continued existence and evasion of predators is testament to his superior genes.  It is not the genes of the tail itself which are desirable, but the genes which allow the bird to maintain the tail.

Which brings us back to Adam Levine and his Minnie Mouse impression.  Many sexual signals have to do with cost, i.e. I can grow and keep this enormous tail and still have enough energy to walk and eat and mate – I must therefore be a genetic dynamo.  Perhaps Adam Levine’s vocal stylings are a perverse sort of honest sexual signal.  Perhaps, when he whinnies, “Following, following, following”, what he’s really saying is, “I am so sexually attractive that women will want to sleep with me even if I sound like a member of the Lollipop Guild”.  Maybe, just maybe, it takes a really big man to sing in such a wee voice.

Or maybe not.


Stanley Milgram and ‘Obedience to Authority’ – Part 3


See Part 1: Shock, and Part 2: Pessimism.

The assumption that informed all of Milgram’s experiments was that his experimental subjects weren’t naturally malicious, and wouldn’t shock another volunteer of their own volition.  He had ample evidence in the reactions of his subjects, in their reluctance and anguish.

And he demonstrated it directly.  In one experimental permutation, Milgram had the experimenter instruct the teacher, from another room, via a telephone.  The set-up and the instructions were identical – the experimenter insisted just as strenuously on escalating the level of shock.  The only difference was the physical absence of the lead investigator.  When he was out of sight, the percentage of subjects who were obedient to the maximum level of shock fell from 65% to 20%.

“Moreover, when the experimenter was absent, subjects displayed an interesting form of behavior that had not occurred under his surveillance.  Though continuing with the experiment, several subjects administered lower shocks than were required and never informed the experimenter of their deviation from the correct procedure.  Indeed, in telephone conversations some subjects specifically assured the experimenter that they were raising the shock level according to instruction, while, in reality, they repeatedly used the lowest shock on the board.”

Then Milgram tried something interesting: he gave the teacher two peers, also secretly confederates of the experimenter, who would refuse to deliver shocks when the student expressed discomfort.  The confederate teachers would move to the other side of the room, saying things like, “I’m willing to answer any of your questions, but I’m not willing to shock that man against his will.  I’ll have no part of it.”

Milgram Peers

When in the presence of these braver peers, 90% of Milgram’s subjects refused to follow through to the end of the experiment.

“The effects of peer rebellion are very impressive in undercutting the experimenter’s authority.  Indeed, of the score of experimental variations completed in this study, none was so effective in undercutting the experimenter’s authority as the manipulation reported here.”

Milgram understood well what his research showed, and what it meant.  If most people are merely obedient, then a very few truly bad actors can do an inordinate amount of damage.

“Any competent manager of a destructive bureaucratic system can arrange his personnel so that only the most callous and obtuse are directly involved in violence.  The greater part of the personnel can consist of men and women who, by virtue of their distance from the actual acts of brutality, will feel little strain in their performance of supportive functions.  They will feel doubly absolved from responsibility.  First, legitimate authority has given full warrant for their actions.  Second, they have not themselves committed brutal physical acts.”

But Milgram gives us reasons for optimism as well as pessimism.  No one who reads his experiments should feel righteous – everyone is implicated.  But even if we look weak, or cowardly, or gullible, through Milgram’s lens, we don’t look cruel.  Time and time again, in Milgram’s experiments, our better nature peeks through, when someone else sets a good example, or when the experimenter is out of the room.  If there’s one lesson in Milgram, it’s not that we’re obedient murderers; or, it’s not that we’re necessarily obedient murderers.  Rather, it’s that we’re essentially unresolved: all it takes is a little push, in either direction.  We’re able and willing to shock a man to death, sure, but we’re also able and willing to refuse.

Or, as Milgram put it:

“Those who argue that aggressive motives or sadistic instincts are unleashed when the command to hurt another person is given must take account of the subjects’ adamant refusal to go on in these experiments.  It is not what subjects do but for whom they are doing it that counts.”

I strongly recommend reading Milgram’s own writing about his work, Obedience to Authority: An Experimental View.  He tried a great number of experimental variables, and he discusses them clearly and succinctly.

Stanley Milgram and ‘Obedience to Authority’ – Part 2


See Part 1: Shock

As the title of his book suggests, Milgram believed that, when his subjects shocked the screaming students, they were not acting out of sadism – they were responding to the authority of the experimenter, backed as he was by the authority of Yale, of higher education, of class, of science.  That authority both allowed the subjects to believe that the experiment was always under control, and that they were not ultimately responsible for the outcome.

To test that hypothesis, Milgram tried two experimental manipulations (actually, he tried many, but there are two I want to focus on here).  In the first, a third experimental subject (also a confederate) was introduced.  Milgram called this new figure the ‘common man’.  In this new scenario, the experimenter left the room on a pretense, and left the ‘common man’ in the role of overseer.  Once alone, the common man shared a neat idea he’d had: to escalate the level of shock every time the student got an answer wrong.

Milgram Common Man

The common man made all the same arguments that the experimenter made in previous iterations of the experiment; the only difference was his lack of perceived authority.  Milgram found that, when the common man gave the order to shock the student, the teacher was dramatically less likely to comply.  Obedience fell from the baseline 65% to 20%.

In the second experimental permutation, through a ruse, the experimenter himself was put in the student’s chair, ostensibly to demonstrate to the reluctant volunteer-student that the procedure was safe.  He instructed the teacher to increase the shock every time he, the experimenter/student, answered incorrectly.  And then he began to answer incorrectly.

Milgram Experiment:Student Sole Authority

In that experiment, the moment the experimenter/student expressed discomfort, every single teacher immediately stopped the shocks and refused to proceed.

“At the first protest of the shocked experimenter, every single subject broke off, refusing to administer even a single shock beyond this point.  There is no variation whatsoever in response…Many subjects explained their prompt response on humane grounds, not recognizing the authority aspect of the situation,

Apparently, it is more gratifying for the subjects to see their action as stemming from personal kindness than to acknowledge that they were simply following the boss’s orders.  When asked what they would do if a common man were being shocked, these subjects vehemently denied that they would continue beyond the point where the victim protests.”

However, that unanimous refusal to obey only happened when the experimenter/student was the sole experimental authority.  Milgram then put two experimenters in the room, and had them pretend that the second volunteer was a no-show.  The two experimenters, in full sight of the teacher-to-be, decided that it was better to run the experiment with one of them as the student than to fail to meet their experimental quota.  They then flipped a coin, the loser took the student’s chair, and the experiment proceeded as per usual.

Milgram Experiment:Student

Milgram found that when an authority instructed the teacher to deliver a shock, even when the victim of the shock was another authority, the teacher complied.

“The experimenter, strapped into the electric chair, fares no better than a victim who is not an authority at all…In total he is no better treated than an ordinary person in the same situation.”

Next week, Part 3: Optimism.

Obedience to Authority: An Experimental View, by Stanley Milgram.

Stanley Milgram and ‘Obedience to Authority’ – Part 1


If you were searching for evidence of the essential goodness of humanity, you probably wouldn’t go looking in Stanley Milgram’s experiments.

Milgram’s famous shock experiments were conducted at Yale University between 1960 and 1963, when he was a member of the Department of Psychology.  Like so many people who had been horrified by the revelations that came during World War II, Milgram was interested in the capacity of normal people to commit brutal acts, especially under orders.  His experiments were designed to explore that capacity, and his findings, which have become notorious, were, and are, disquieting.

In those experiments, subjects were told that they were participating in a learning trial, a word-recall task.  They and another volunteer (secretly a confederate of the experimenter, a plant) drew lots: the game was rigged, and the subject always drew the role of the ‘teacher’, and the confederate the role of the ‘student’.  The student was seated out of sight of the teacher, who would read word pairings to him.  Whenever the student recalled a pairing incorrectly, the teacher was instructed to give him one in a series of escalating shocks.  The experimenter looked on, directing and encouraging the teacher.

Milgram Basic

The teacher administered the shocks from a shock generator with switches which generated voltages from 15 to 450 volts.  In order to drive the point home, these switches were labelled in groups designated Slight Shock, Moderate Shock, Strong Shock, Very Strong Shock, Intense Shock, Extreme Intensity Shock, Danger: Severe Shock, and XXX (editorial sidenote: ‘XXX’? Really? ‘XXX’ should have been a dead giveaway that there was funny business going on with this experiment).

Shock Generator

The student, who in reality received no shocks at all and who answered incorrectly deliberately, expressed escalating discomfort, claimed a heart condition, begged to be released, screamed in agony, and finally fell silent and stopped responding in any way.  If the teacher expressed reservations, or tried to stop the experiment, the experimenter instructed him to continue, insisting if necessary, and assured the teacher that the student was perfectly safe and that the experiment was under control, even while the student screamed that he was having heart pain.  Even when he went silent.

Most of the subjects expressed distress at what they were doing.  They asked to stop, tried to insist.  However, only a minority actually stopped.  In Milgram’s original experiment, 65% of his 40 experimental subjects obeyed the experimenter and shocked the student to the maximum 450 volts.  These were clearly labelled lethal levels of shock, and 65% of normal volunteers continued to shock a screaming, begging man to the end.

And that was the message that most people took away from Milgram’s study.  The New York Times wrote, in 1963, “A study at Yale University to assess the extent of such blind obedience found that an unexpectedly large proportion of a test population would follow orders, even if they could see that they were inflicting severe pain.”

But Milgram’s studies were more complicated, nuanced, and thorough than most people realize.  In 1974, Milgram published his complete experiments and analysis in his book ‘Obedience to Authority: An Experimental View’.  The picture of our nature which emerges from that work is murkier than the New York Times supposed.

 Obedience to Authority: An Experimental View, by Stanley Milgram.

The Westermarck Effect

In the late 1800s, Edward Westermarck was sitting around and thinking about the incest taboo.

Across the world and throughout history there have been strict taboos against sexual relationships between close blood relatives (with a few notable and creepy exceptions – most famously among royals in Ancient Egypt: Cleopatra, for example, married her brother).  While the specific definition of “close” varies from culture to culture and time to time, sexual or marital relationships between siblings or between parents and children are almost universally prohibited.

When Edward (or Edvard) Westermarck was doing his thinking, it was the opinion of many learned men that the incest taboo was a societal construction.  Sir James Frazier, one of Westermarck’s critics, wrote of the incest taboo that “the law only forbids men to do what their instincts incline them to do”, which perhaps says more about Sir Frazier than about men in general.

Westermarck, however, apparently didn’t want to have sex with his close relatives, and didn’t believe that the incest taboo was a top-down cultural regulation.  He noticed that most people, rather than longing desperately to have sex with their relatives and sitting on their hands for the sake of the law and the neighbors, felt a profound and visceral disgust at the idea of incest.

Westermarck hypothesized that there might be a critical period during childhood development, and the people to whom a child is heavily exposed during that critical period will never be sexually attractive to them.

With the shadow of Freud looming over everyone and insisting that it was completely normal to want to have sex with your mother, psychologists and biologists cheerfully ignored Westermarck for decades.

In the past fifty years, however, scientists have gone looking for evidence of the Westermarck effect (which is also called ‘reverse sexual imprinting’).  The first evidence came from observations of several species of macaque monkeys.  Scientists (Sade most explicitly, in 1968) discovered that, despite the Freudians, monkey sons don’t have sex with their mothers.  When male animals win their way to the alpha spot in their troop, they take sexual advantage of their new position, and mate with all the females in the group, except their mothers.  Even in animals groups where sexual pairings are relatively indiscriminate, males sexually avoid their immediate blood relatives.

Only among scientists, who had to retreat to the lab to rediscover something as basic as maternal love, would the information that sons don’t want to have sex with their mothers come as breaking news.  But they finally discovered it, after all, several decades too late for poor Westermarck, who died in 1939.

Featured image is a bronze coin of Cleopatra from the collection of the British Museum.

Isaac Newton, His Eye, and His Bodkin


Adventures in Physics!

bodkin (noun):

1. a) a dagger or stiletto

   b) a sharp, slender instrument for making holes in cloth

   c) an ornamental hairpin shaped like a stiletto

2. a blunt needle with a large eye for drawing tape or ribbon through a loop or hem

Bodkin from Museum of London

This is a bodkin.

(from The Museum of London)

Picture 4165

This is also a bodkin.

(from The Imperial War Museums)

The reason I mention bodkins is that I learned this week that Sir Isaac Newton, considered by many to have been an intelligent man, spent some time in the 1660s sticking one into his eye.  On purpose.

Newton was famously interested in optics and the nature of light.  However, he was also interested in the visual stimulus, and the physiological processes by which objective reality is perceived by us.

So, to address this question, Sir Isaac Newton thought it would be sensible to start poking himself in the eye with a large needle.  We know this because, like any good scientist, Isaac Newton left detailed experimental notebooks.  He even included helpful illustrations.

Bodkin in Eye

From the Cambridge University Library

And therein, perhaps, lies the difference between the dedicated scientist and the layperson.  It would take a great deal of persuasion to get a normal person to poke themselves in the eye with a needle – Isaac Newton did it because he hoped he might learn something about color.

And did he?  Well, sort of.  He learned that, when you poke yourself in the eye, you disrupt your vision.  When he stuck the bodkin between his eyeball and his eye socket, “as neare to backside of my eye as I could”, then he saw spots.  Those spots were clearest “when I continued to rub my eye [with the] point of bodkine”.

That’s science, baby!

I first heard about Isaac Newton poking himself in the eye for science in The Clockwork Universe: Isaac Newton, the Royal Society, and the Birth of the Modern World, by Edward Dolnick, a book completely worth picking up if you have any interest in the history of science.