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81
CHAP TER 5
A Chromosome for Maleness
In his popular 2003 book Adam’s Curse, Oxford University geneticist Bryan Sykes describes his fi rst glimpse of “the DNA that had made me a man”:
This is my Y-chromosome, the bearer of my maleness and the token
passed unaltered down from a long line of fathers. This is the chro-
mosome I have come to see. I see it in my own father, as he leads his
RAF squadron in the Second World War. I see it in my grandfather,
fi ghting in the trenches and wounded in the battle of the Somme a
generation earlier. . . . It is only my Y chromosome that now speaks
with a single voice, one that has come to me from generations
of men.1
In the book, Sykes animates the Y chromosome as the transcendent es- sence of maleness, shared by all men in genetic fraternity, and presses the Y into a nostalgic patrilineal narrative of family, blood, and ancestry.2 Retelling history through the eye of the Y, Sykes depicts Genghis Khan’s infamous violent temper and legendary promiscuity as driven by “the ambition of his Y chromosome.”3 According to Sykes, throughout hu- man evolution, the Y compelled male sexual appetite, aggression, rape, and pursuit of wealth and power: “Forced by the relentless ambition of the Y chromosome to reproduce itself, women were reduced to a state of
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serial pregnancy, increasingly enslaved by dependence on men. . . . Men, driven on by the lash of their Y chromosomes, could copy their cattle and become the stud bulls of their own herd.”4
Conceptions of the Y as male, and as the molecular agent of mascu- linity, are ubiquitous in popular and scientifi c writing on the sex chro- mosomes today. In his 2002 Y: The Descent of Men, geneticist Steve Jones dubs the Y the “vessel of manhood” and asserts that “the chromosome unique to men is a microscopic metaphor of those who bear it.”5 He con- tinues: “Important as experience can be, the contents of a boy’s skull are infl uenced by messages, both direct and indirect, from his insidious Y chromosome. From his earliest days his brain, like his body, is to some degree under its control.”6 Similarly, Craig Venter, the biotech entrepre- neur who succeeded in sequencing the human genome in 2001, writes in his 2007 autobiography A Life Decoded, “I never fully got over what I viewed as my father’s betrayal, which I considered even worse than hav- ing a gun pointed at me. I can blame it all on the Y.” We also learn of his fi rst sexual conquest: “My Y came into its own when Kim had a Sweet Sixteen party while her parents were away.”7
Here I explore the origins of these associations between the Y, male- ness, and masculinity and investigate their infl uence on human sex chromosome research in the twentieth century. One might imagine that the Y would be an uncontroversial case of a chromosome with a “sex.” Since 1959, we have known that without a Y chromosome—or at least without the gene it carries that is needed for testes determination—the developing fetus will not become a male. Moreover, only males have a Y.8 But outsized conceptions of the Y as the seat of biological maleness and the essence of masculinity are not fi xed by these facts. These conceptions have a history and a context. They were developed and hardened within the particular dynamics of mid-twentieth-century cytogenetics, behav- ioral genetics, and sociobiology.
XYY “supermale” theories in the 1960s and 1970s, which asserted that males with an extra Y were bigger, taller, and more aggressive—more male—represent the fi rst episode in the construction of the notion of the Y as the chromosome for maleness. Today scientists regard XYY as an embarrassing episode in the history of genetics. The studies were char- acterized by notorious empirical and methodological failings. In what follows, I show how a working model of the Y as the specialized agent of maleness, a model that draws on ideological conceptions of gender in the 1960s and 1970s, played a central and signifi cant role in the development of the fl awed hypothesis of an XYY supermale syndrome. The model of
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A Chromosome for Maleness 83
the Y chromosome that was advanced by XYY research—that the Y is the genetic substrate of “maleness”—would carry into the molecular era, and continues to infl uence both popular and scientifi c conceptions of the Y chromosome today.
A DOUBLE DOSE OF MALENESS
Research on the human Y chromosome, the genetic marker of male sex and the carrier of the testes-determining gene, began in the 1950s. First observed in insects in 1905, the Y’s function in humans was disputed until 1959, when the fi rst trait was linked to the human Y: the male sex- determining factor.9 In 1959 and 1960, a series of clinical case reports showing XXY, XXXY, and even XXXXY genotypes leading to normal (if infertile) phenotypic males fi rmly established the Y—not the X, as previ- ously believed—as the marker of male sex (see fi g. 5.1).10
Figure 5.1. Sex chromosome aneuploidies demonstrating that the Y chromosome carries the male sex- determining factor. Reprinted from K. R. Dronamraju, “The Function of the Y-Chromosome in Man, Animals, and Plants,” Advances in Genetics 13 (1965): 227–310, with permission from Elsevier.
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Despite its link to male sex determination, the Y, an unusual chro- mosome that is one-twentieth the size of the X, was of little interest in the early 1960s. It was considered too skittish and small for cytogenetic analysis. Most geneticists assumed that it was genetically inert, carrying little other than the male testes-determining gene, until blood samples collected during routine physicals of 197 patients at a high-security psychiatric hospital in 1965 revealed an unexpectedly large number of males—3.5 percent—with an extra Y chromosome.11
Patricia Jacobs, the Edinburgh cytogeneticist famous for identifying the Klinefelter’s (XXY) genotype in 1959 at the precocious age of twenty- three, conducted the study. In the 1965 Nature paper reporting the study’s fi ndings, Jacobs hypothesized that “an extra Y chromosome predisposes its carriers to unusually aggressive behavior” and that “we might expect an increased frequency of XYY males among those of a violent nature.”12 Jacobs’s attribution of the larger representation of XYYs in security facili- ties to a double dose of Y-linked aggression framed the next fi fteen years of research on the human Y chromosome.
In a 2006 interview, Jacobs recounted the path of reasoning that led her to hypothesize a link between the Y and aggression. In 1960, reading a Swedish study that showed an overrepresentation of extra-X, or XXY, individuals in institutions, Jacobs noticed an apparent overrepresenta- tion of the very rare genotype XXYY. As Jacobs recalls, “a very signifi - cant proportion were XXYY . . . and I said to [my colleague]: ‘That’s far too many XXYYs . . .’ and he said ‘No, it’s just chance.’ I thought, I don’t think it is.”13
The arrival of the XYY male initiated the fi rst serious cytogenetic stud- ies of the Y chromosome. Research on the so-called supermale fl ourished in the United States, Britain, and Denmark during the 1960s and 1970s. The so-called XYY syndrome was a mainstream target of investigation in the most prestigious journals of biology, genetics, and cytogenetics. In 1970, the US National Institutes of Mental Health (NIMH) published an eighty-page “Report on the XYY Chromosome Abnormality,” a move that conveyed a high-level sense of urgency about XYY males and fortifi ed the impression that XYY was a veritable medical disorder and a serious factor in criminal sociopathy.14 The link between XYY and aggression was hotly pursued. According to the Pubmed research database, by 1970, nearly two hundred papers on the link between XYY and aggression had appeared in the scientifi c literature. Between 1960 and 1970, XYY re- search comprised 82 percent of all published scientifi c studies on the human Y chromosome. It accounts for 28 percent of the entire body of
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A Chromosome for Maleness 85
Y chromosome research generated in the quarter-century between 1960 and 1985.15
XYY research propelled the Y into the cultural lexicon as a molecu- lar symbol of masculinity, similar to testosterone. Extensive print and television media images of XYY criminals tended to accentuate their height, muscularity, and sexuality. High school and college biology and psychiatry textbooks in the 1970s rapidly incorporated the idea of the XYY super-aggressive male, often featuring an image of 1970s serial killer Richard Speck (though Speck was not, in fact, XYY). Popular cultural forms reinforced this link between the Y and masculine behavior. As Jer- emy Green, a British science studies scholar whose 1985 account of the XYY episode remains the principal secondary historical literature on it, records, “by the early 1970s, there had been at least two ‘thriller’ fi lms in which the main character is a violent criminal driven by a chromosome abnormality, a series of crime novels with an XYY hero (who constantly wrestles with his inner compulsion to commit crimes), and as a spin-off from the novels, a TV series called ‘The XYY Man’” (see fi g. 5.2).16
Writers and cultural critics began using the term “Y chromosome” as a synecdoche for a man. The Oxford English Dictionary cites Peter Cave’s 1974 Dirtiest Picture Postcard as the earliest English-language usage of the Y chromosome in a nonscientifi c text: “You’ve buttonholed me to give me long and boring lectures upon Germaine Greer, the faulty Y chro- mosome and the drudgeries of housework and child-bearing.” In 1982, Edgar Berman wrote in The Compleat Chauvinist, “from that constantly on-the-make little tree mouse . . . to Mailer the magnifi cent, the DNA of the male Y chromosome has programmed us to lead our sisters.”17
It took enormous resources and more than a decade of work by mul- tiple research groups to reverse Jacobs’s initial conjecture. Through large epidemiological studies published in 1976 and 1977, researchers proved that 97 percent of XYY individuals will never commit a crime, that the higher prevalence of XYYs in security institutions than the general population was due, if anything, to slightly lower median intelligence, that their offenses were actually less aggressive and violent than those of their fellow XY inmates, and that the only phenotype reliably asso- ciated with XYY was increased height.18 This profi le of the XYY male showed that any behavioral differences in XYYs were due to a generalized developmental effect, consistent with a chromosome imbalance, not a double dosage of Y-chromosomal genes specialized for aggression or vio- lence. XYY vanished almost completely from the scientifi c literature by 1980.
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Figure 5.2. XYY Man book cover. Reprinted from Kenneth Royce, The XYY Man (New York: McKay, 1970).
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A Chromosome for Maleness 87
BIAS IN XYY RESEARCH
Today the XYY syndrome stands as an exemplar of discredited science and poor genetic reasoning. The overwhelming majority of interpreters agree that XYY research in the 1960s and 1970s was marked by bias, distortion, and gaps in reasoning. Methodological failings of these stud- ies, many of which were raised at the time, included:
1. Small sample size. XYY individuals are very rare (about 1 in 1,000
males). In the small institutionalized populations studied, a single
false positive would dramatically change the estimate of prevalence
rates of XYY in prisons.
2. Biased samples. Researchers studied XYY only in incarcerated individ-
uals in “high-security” institutions and did not study nonincarcer-
ated men. This was, of course, a biased sample, including only indi-
viduals already deemed “criminal” or “aggressive.”19
3. Lack of double-blind protocol. Most early studies, including the 1965
study by Jacobs, did not use double-blind procedures, but set out spe-
cifi cally to screen for XYYs. This created the likelihood that “wishful”
false positives slipped into the data.
4. Poorly defi ned phenotype. The phenotype of “aggression,” which was
defi ned by the fact of subjects’ incarceration rather than specifi c be-
haviors they exhibited, lacked rigor.
5. Neglect of environmental variables. XYY researchers failed to profi le the
family, social class, and medical background of their subjects, data es-
sential for testing the viability and strength of any behavioral genet-
ics claim.
6. Lack of plausible mechanism; no experimental confi rmation. Researchers
never offered a molecular or evolutionary mechanism for how an ex-
tra Y might carry the specifi c behavioral phenotypic consequence of
criminal aggression, nor did they propose, or attempt to carry out,
human or model organism experiments that might test this causal
link.
The XYY theory also leaned on questionable biological assumptions and ignored contradictory evidence. Two issues in particular stand out. First, the XYY hypothesis defi ed the conventional framework for under- standing how supernumerary chromosomes affect phenotype. As Green noted, researchers assumed that the Y chromosome “would make a spe- cifi c contribution to violence or aggression, instead of having the generally impairing effects associated with an extra chromosome.”20 According to
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this double-dosage model, the extra Y doubled the contribution of a pu- tative gene for “aggression” in a male, rather than producing complex, global developmental effects, as in the case of Down’s syndrome (trisomy 21). Second, XYY researchers ignored a supremely problematic piece of evidence that contradicted the idea that a connection between the Y and aggression exists. Despite the fi nding that extra-X, or XXY, men were as prevalent as XYY individuals in security institutions, researchers associ- ated aggression with the Y chromosome and not the X.
For all of these reasons, scholars today often hold up XYY studies as a classic example of poor reasoning in human behavioral genetics. Despite this, scientists invested nearly two decades of research efforts and fund- ing in XYY studies. Even principal actors in the XYY controversy are at a loss to explain what went wrong in retrospect. Refl ecting on the research blunders of XYY studies, Saleem Shah, the head of the NIMH juvenile crime unit and coauthor of several key publications on XYY, has said, “It is diffi cult to know what people’s motives were for doing these studies. I have given up trying to fi gure out what the real facts are, because I do not know what they were. It depends, I suppose, on what you consider ‘real.’”21 In the aftermath of the XYY episode, geneticist Jonathan King, a critic of the XYY studies, was similarly fl ummoxed: “The interesting question is why the whole history of studies in this fi eld were [sic] so full of biases and distortions. . . . Valid criticisms of those studies were made from the very beginning. They had much publicity and for various rea- sons were not widely circulated.”22
The received view of XYY research among scientists today is as an “embarrassing” incident of mishandled public relations in the history of behavioral genetics.23 In the decades following the XYY episode, many scientists disavowed it as a case of media sensationalism, portraying the idea of the XYY supermale as a marginal theory that was rapidly de- bunked and renounced by geneticists but that nevertheless lived on in the media.24 For instance, James Watson’s important textbook, Recom- binant DNA, mentions XYY, but only as a cautionary tale of a poorly con- ceived line of research, which because of media distortion and amplifi ca- tion wrongly stigmatized XYY individuals.25
In his 1985 study, Green, a scholar in science studies and communi- cations, analyzed media coverage of XYY research. Green showed that it was prominent scientists who hyped the XYY hypothesis, drawing on popular “expository strategies,” while journalists were more willing than the scientists to raise questions and rein in incautious interpretations of the link between XYY and aggression.26 Indeed, scientists used news- paper interviews “as an opportunity to present their more creative, and
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A Chromosome for Maleness 89
less empirical interpretations and speculations.”27 Green concluded that the media did not create a “myth” of the hyperaggressive XYY male, but accurately conveyed the already sensationalized endorsement that scien- tists gave to this image of XYY men.
Green attributes scientists’ fever for the XYY hypothesis, despite its weak foundations, to two historical factors. He suggests, fi rst, that an “upsurge of interest in crime . . . [and] the apparent failure of programs based on social intervention” in the 1960s and 1970s stimulated research on human aggression and encouraged researchers to overstate their claims.28 Unfortunately, any evidence for the existence of a connection between crime waves in the 1960s and 1970s and XYY research is tenu- ous. While it is certainly plausible that XYY researchers imagined that genetic studies could help to solve crime problems, any such hope would have been in the broadest of generalities. Crime was not a matter of seri- ous academic interest, nor of any demonstrative applied practice, among XYY researchers. Cytogeneticists with no specialty in crime led the re- search effort. Their use of men in prison populations as study subjects was a matter of happenstance and convenience of access, not interest in criminal behavior. Biologists, not criminologists, were the principal agents of XYY research. Indeed, biological theories of criminal behavior ran directly against the current of the fi eld of criminology at the time.
In contrast, amongst US geneticists, the notion that genetics could explain individual and community variations in behavior was profes- sionally and institutionally on the rise during these exact years. The fi rst textbook on behavior genetics appeared in 1960.29 The fi eld entered the wider public and scientifi c consciousness with Arthur Jensen’s infamous 1969 article asserting that the racial IQ gap was genetic and hereditary.30 In 1970, the Behavior Genetics Association and the fi rst scientifi c journal devoted to the subject were founded. Aggression was a topic of particu- lar interest in this fi eld. During the 1960s and 1970s, psychiatrists were beginning to conceptualize human aggression as a brain abnormality with an organic and likely a genetic basis.31 As we shall shortly see, this newly intense focus on innate and inherited human behavioral traits also found traction in other fi elds, including ethology, physical anthro- pology, and sociobiology.
The spread of these developments to applied fi elds such as criminol- ogy would come later.32 Mainstream criminology in the 1960s still asso- ciated crime primarily with mental health, youth, and social class, factors that were understood to impact males and females differentially because of the cultural infl uence of sex roles.33 There were few sympathetic ears for the XYY hypothesis in the crime control community. While some
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geneticists, such as Richard Lewontin and Jonathan Beckwith, criticized XYY studies, aggression researchers from psychology, endocrinology, and criminology, more sensitive to the nuances and methodological require- ments of behavior studies, led the way and were among the earliest and most vocal critics of XYY research.34
The second factor named by Green is the competitive race for chro- mosomal disease correlations during the 1960s heyday of cytogenetics. XYY surfaced at the height of cytogenetics, just after new techniques had given rise to a series of dramatic fi ndings that linked chromosome abnormalities to human phenotype, including the unambiguous associa- tion of Down’s syndrome with the presence of an extra chromosome 21. Like the gene-discovery race of the 1980s, in the late 1950s and early 1960s researchers competed to identify new chromosomal abnormalities, hyped as the key to much of human diversity as well as to the origins of debilitating diseases and birth defects.35 Green suggests that researchers, swept up in the frenzy, prematurely and overconfi dently linked dramatic behavioral effects with the XYY genotype. Yet despite this heady im- mediate scientifi c context of XYY research, there are not parallel cases of fl agrant bias and runaway hypothesizing in the case of other non– sex chromosome abnormalities during this period. That is, something in particular about the notion of an extra sex chromosome led researchers astray. To account for the specifi cities of the methodological errors and biases that characterized XYY research, we must look to another cen- tral aspect of the development of the hypothesis: popular and biological ideas about gender in the 1960s and 1970s.
BIOLOGICAL THEORIES OF SEX DIFFERENCE
IN THE 1960S AND 1970S
In what follows, I argue that prevailing biological theories of sex differ- ences constituted the background explanatory framework within which XYY theories were received and understood in the 1960s and 1970s. XYY studies originated not among psychologists or criminologists, but among molecularly inclined biologists and those in the nascent fi eld of behavio- ral genetics, who treated XYY research primarily as concrete evidence of a genetic basis of behavioral differences between the sexes. Specifi cally, the XYY supermale hypothesis was conceived, and received, within an associative framework of biological claims about male aggression, human nature, and sex and gender difference in the 1960s and 1970s.
During the mid-twentieth century, physical anthropologists devel-
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A Chromosome for Maleness 91
oped a theory of human cultural evolution centered on the “man the hunter” and “woman the gatherer” gender roles. The idea that men are primarily adapted to be hunters—aggressive, competitive, physical, ac- tive—became the foothold for theories of human sex differences across many areas of biology. Man-the-hunter came to be understood as an ex- planation for why, as Lewontin, Rose, and Kamin quipped in their fa- mous critique of this view of human nature, Not in Our Genes, “today men are executives and women are secretaries” and “why we sometimes behave like cavemen.”36 As Lewontin and colleagues noted, such argu- ments were ideologically convenient, entering a contentious wider soci- etal debate over gender roles in the 1960s and 1970s. Just as women’s lib- eration movements were challenging the traditional gender order, a new science emerged that suggested, wrote Lewontin et al., “that sexual divi- sions have emerged adaptively by natural selection, as a result of the dif- ferent biological roles in reproduction of the two sexes, and have evolved to the maximal advantage of both; the inequalities are not merely inevi- table, but functional, too.”37
Texts publicizing these theories of the evolution of human sex differ- ences, such as Desmond Morris’s The Naked Ape (1967), Lionel Tiger’s The Imperial Animal (1971), and David Barash’s The Whisperings Within (1979), circulated widely during the 1960s and 1970s.38 This literature, which would form the foundations of the new fi eld of sociobiology, portrayed modern man as an animal honed by evolution for violence and conquest, a beast contained and restrained by the manners and restrictions of con- temporary society. The claim that males are naturally more aggressive than females was arguably the central premise of sociobiological theories of biological sex roles.39 Sociobiologists cited men’s higher aggression to explain why they are better at math and abstract thought, more suited for leadership roles, prone to rape, attracted to pornography, and ill suited for monogamy. Men’s innate aggression was even said to explain features of human culture and society such as capitalism, imperialism, and war.
In the context of this general approach to the evolutionary history of sex differences, the XYY male appeared as a well-timed confi rming example. Within this associative framework, XYY offered a forceful piece of evidence that a certain level of male aggression—in the ordinary XY male—was both normal and natural. As Curt Stern, the eminent Ameri- can geneticist and author of the authoritative genetics textbook of the 1960s, speculated in a 1968 New York Times article on XYY, “the female sex owes its gentleness to the absence of a Y chromosome and the nor- mal male his moderate aggressiveness to the single Y.”40 Kurt Hirschhorn, chief of medical genetics at Mt. Sinai School of Medicine, explicitly con-
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92 Chapter Five
nected XYY research to then-emerging sociobiological conceptions of masculinity and aggression:
What if the genes for aggression and tallness do exist in the Y? They
would have had survival value for the caveman, and there might
have been an evolutionary selection for them. But civilized man has
been breeding against aggressive genes. . . . The average male has
just the single Y. Now, today, we fi nd a man who gets a double dose
of Y’s; it’s understandable that they might well be too much for him
to handle.41
This logic appears in the actual research studies as well. As one XYY study stated, “the XYY genotype may be seen as highlighting the associa- tion between maleness and violence. . . . If the genes on a single Y chro- mosome of a given individual are such as to produce a tendency toward marked aggression, then a double dose of such a Y chromosome would be expected to lead to extreme aggression.”42 Consistent with sociobio- logical models of sex differences, here the Y chromosome is portrayed as encoding atavistic traits, once adaptive, that emerge when the Y dosage is upped by an accident of nature. Within the biologically determinist and traditional gender-ideological worldview of sociobiology, many received the association between the Y and aggression as confi rmation of the nat- uralness of normal male aggression and as evidence that contemporary gender roles are based on innate biological sex differences.
ACCOUNTING FOR BIAS IN XYY RESEARCH
Understanding the infl uence of the emergent sociobiological model of sex differences in 1960s and 1970s biology helps make sense of the unstated assumptions and inferences that glued the XYY hypothesis together. To proceed with the hypothesis of Y-linked aggression, researchers had to ignore standard explanatory frameworks and data that clearly opposed it. The alignment between a model of the Y chromosome as specialized for male-stereotyped behavior and mainstream contemporary theories of sex differences made this possible. Compared to XX individuals, XY individuals were overrepresented among violent criminals, so research- ers reasoned that XYY individuals should be expected to be even more overrepresented. As Jacobs recalls, “so I thought, that’s very funny isn’t it? Maybe the Y is affecting their behavior. Well that’s quite likely isn’t it? If you stop and think about it, ninety-eight percent or some such number
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A Chromosome for Maleness 93
of the prison population are males. So you can’t say the Y has got nothing to do with behavior.”43 Friedrich Vogel and Arno Motulsky would later summarize the chain of reasoning in their 1979 genetics textbook: “Nor- mal men are more aggressive than normal women; normal men have one Y chromosome, women do not. Hence, if someone has two Y chro- mosomes, he should be twice as aggressive as normal men.”44 The cru- cial point here is that Jacobs’s hypothesis was not specifi cally about XYY males; rather, it was that we should expect the Y chromosome to contain the genes for stereotypic male traits, aggression foremost among them. That the Y was the obvious substrate of maleness went unquestioned, not just by Jacobs but by most geneticists at the time.
The XYY “supermale” theory fl ew in the face of customary ideas about extra chromosomes. Geneticist Park Gerald, leader of a major Harvard XYY study, called the XYY complement a “supermaleness syndrome” in a press conference, and the New York Times quoted geneticist Curt Stern referring to XYY as “double Y aggressiveness.”45 Yet, the prevailing hy- pothesis at the time was that chromosomal disorders, such as Down’s syndrome (trisomy 21), produced phenotypic abnormalities by general chromosomal imbalance, rather than through the duplication of specifi c genetic material. An additional chromosome was thought to produce an imbalance of gene product and not a simple doubling of it. Explaining chromosomal aneuploidy in his 1965 textbook An Introduction to Human Genetics, Eldon Sutton, who would become president of the American Society of Human Genetics in 1979, nicely captured this prevailing view: “Since the genes on a particular chromosome may be quite unrelated in their primary action, trisomy would disturb many apparently unrelated functions.”46 Genes work together in complex regulatory relation. An ex- tra chromosome can have very specifi c characteristic effects, but these effects are unlikely to simply be “more” of what the genes normally do. Rather, an extra chromosome results in a general, stochastic develop- mental effect of multiple mistimed or diverted genetic pathways. This was the consensus view of the phenotypic consequences of chromosome aneuploidy. Despite this, the leading explanation of the link between XYY and crime in the biology community assumed that the XYY simply provided a double dose of male aggression.
Gender conceptions played a critical role in shaping the conceptual framework within which researchers crafted the XYY theory and help to explain why researchers pursued a double-dosage explanation of super- numerary chromosome behavior in the case of XYY. The symbolic iden- tifi cation of the Y with masculinity, and the confl uence of the double- dosage model of XYY with dominant proto-sociobiological theories that
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saw human males as possessing a “beast within,” led researchers, in the case of XYY, to assert the unlikely double-dosage model over the more validated chromosome imbalance model.
By the mid-1970s it had dawned on many researchers that males with an extra X (XXY or Klinefelter’s males) were also overrepresented in secu- rity institutions. A double-X chromosome complement in males looked to be as predictive of criminality as the XYY complement. Researchers did not know quite what to do with this bedeviling fact. Jarvik et al., among the earliest to raise the issue of XXYs, wrote in 1973: “It would seem . . . that patients in mental hospitals are more prone to have an extra sex chromosome than men in the general population, but that the tendency is nonspecifi c, the probability of an extra X chromosome being as great as that of an extra Y chromosome.”47 Jacobs conceded in 1975 that “the excess of males with an abnormal chromosome constitution in mental- penal settings is not confi ned to XYY individuals but also applies to XXY men.”48 In 1976, Witkin et al. ventured that an extra X or Y may lead to similar behavioral phenotypes with regard to crime: “The similarities between the XYYs and the XXYs suggest that . . . the consequences of an extra Y chromosome may not be specifi c to that chromosomal aberration but may result from an extra X chromosome as well.”49
The profi les of XXYs and XYYs in high-security institutions were in- distinguishable in terms of kinds of crimes committed and representa- tion in institutions of incarceration. Nonetheless, no research program was initiated to study the correlations between double-X and aggression. The association of the XXY with crime had to be ignored or dismissed to sustain the hypothesis of a specifi c association between the Y and aggression. A gendered schema that localized maleness to the Y, along with a corresponding association of the X and femaleness, facilitated the dismissal of the problem that XXY posed to the XYY theory.50 Attempt- ing to hold together the logic of the Y-aggression association, researchers proposed that the presence of XXYs in high-security institutions might be due to different behavior than their XYY counterparts. The hyperfem- inine manners of XXYs—their passivity, emotionality, and subpar intel- ligence—landed them in prisons, while the hypermasculinity of XYYs— their aggression and impulsiveness—led to their institutionalization.
In the 1970s, scientists brought a gendered schema for understand- ing the Y chromosome into their delicate hairsplitting to explain equal XXY and XYY representation in criminal institutions. Leading human population cytogeneticist Michael Court Brown, of the University of Ed- inburgh, for instance, attributed Klinefelter’s criminality to low intelli-
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gence, asserting that XXYs specialized more in property offenses in the range “from larceny to child stealing.”51 In contrast, XYY criminality, he claimed, was due to an “aggressive,” “disturbed pattern of behavior,” “so violent and aggressive that they require to be kept in conditions of maxi- mum security.”52 Geneticist Edward Novitski, author of one of the most widely used human genetics textbooks of the 1970s, solved the quandary by claiming that XXYs show “failure in accomplishing some task, or an inability to do so, a pattern different from that of an XYY.”53 In contrast, he wrote that XYYs show “behavioral problems related to the impulsive, exaggerated performance of a deed that is carried out without regard for the long-range consequences.”54 Reproducing a familiar gendered binary, here XXY criminality results from feminine ineffectiveness and passiv- ity, while XYY criminality is a consequence of a masculine overactive personality. In a similar vein, in the 1980 version of his textbook, Sutton characterized the XXY’s troubles as due to “a slightly increased risk of di- minished intellect and of emotional instability,” while XYY displays “de- structive” sociopathy: “The expression is one of increased impulsiveness with little perception of future consequences.”55 In this case, XXY is fem- inized as overly emotive and XYY masculinized as cold and unfeeling.
Male identifi cation of the Y, along with a corresponding female iden- tifi cation of the X, contributed to a distorted model of the genetics of male aggression and led XYY researchers in the 1960s and 1970s to ne- glect alternative models of the relationship between sex chromosome ab- normalities and behavioral phenotype. Gender beliefs help to explain this stubborn identifi cation of the Y chromosome with maleness and aggression, and the inability of midcentury XYY research to see, take up, or account for a similar criminal profi le of multiple-X-chromosome individuals.
THE FOLDING OF XYY RESEARCH
By 1982, Patricia Jacobs, delivering an address to the American Society of Human Genetics, would refl ect back on “the end of an era” of XYY research (and cytogenetics as a whole), now eclipsed by the “day and age of restriction enzyme polymorphisms, transposable genetic elements, in- trons and exons.”56 After the downfall of XYY, Jacobs left the high-status Edinburgh cytogenetics lab for Hawaii, “for an empty laboratory in a corner of the anatomy department,” and shifted her attention away from the human Y chromosome.57
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For most, the 1976 study published in Science by American psycholo- gist Herman A. Witkin and colleagues put the XYY hypothesis to rest.58 The study included all 4,558 Copenhagen-born males in the Danish na- tional draft registry whose height was greater than 184 centimeters (a subgroup expected to contain a higher rate of both XYY and XXY males than the general population). Researchers visited the subjects’ homes to take buccal smears and blood samples for chromosomal analysis, an ex- haustive effort in which subjects not found at home “were subsequently revisited, up to a total of 14 times in the most extreme instance.”59 Exam- ining claims of an association between XYY and criminality, the study found no difference in the rate of aggressive crimes between XYY and XY individuals. It showed that XYY individuals on average have slightly lower IQs and are a bit taller than the general population, which they speculated may account for their elevated rates of criminal detention. Finally, it showed that the rate of criminal detention for XXY and XYY males was identical. As the authors concluded, “no evidence has been found that men with either of these sex chromosome complements are especially aggressive. Because such men do not appear to contribute par- ticularly to society’s problem with aggressive crimes, their identifi cation would not serve to ameliorate this problem.”60
Suspicions of some underlying truth to the supermale syndrome, however, persisted among some even after the hypothesis was discred- ited in most geneticists’ eyes. In the aftermath, some cytogeneticists be- lieved that research on the XYY hypothesis had been snuffed out before the association between Y and aggression had been thoroughly explored. For some in the Edinburgh, Harvard, Johns Hopkins, and NIMH cytoge- netics communities who had promoted the hypothesis, the perceived proximate cause of the demise of XYY research was public controversy, not an empirical dead end.
In 1975, a controversy erupted over genetic screening for XYY in new- born males at Harvard University’s teaching hospital, Boston Women’s Hospital. One of the largest and most ambitious studies of the phenotypic effects of XYY in young boys, the study described its broad aim as the elucidation of the genetic substrates of sex differences. Wrote Park Ger- ald, the study’s lead investigator and founder of Harvard’s fi rst human genetics research and training program, “we began the study to under- stand the important connection, if any, between genetics and behavior differences between the sexes.”61 The specifi c goal of the study, funded by the NIMH Center for Juvenile Crime, was “a more precise estimation of the risk, if any, to XYY children likely to develop aggressive or psycho-
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A Chromosome for Maleness 97
sexual pathology.”62 Parents of boys identifi ed as XYY would be informed that their child had a sex chromosome abnormality; XYY boys would be subsequently tracked over the years through parental interviews, psycho- logical observations of play and classroom behavior, and other physical and mental measures. It was the largest and most ambitious study of XYY children to date.
Science for the People (SFP), a national group of American leftist sci- entists with a lively cohort at Harvard and MIT, took issue with the XYY study’s biologically determinist model of human behavior and rallied university, legal, and media avenues to stop the study.63 Initiated in 1968 at the height of antinuclear and antiwar activism, SFP fi rst became widely known for its condemnation of Arthur Jensen’s 1969 argument that ge- netic differences account for the IQ and educational achievement gap between whites and blacks in the United States. Later, SFP drew up force- ful responses to E. O. Wilson’s 1970s reinvigoration of neo-Darwinist so- ciobiology, which the SFP condemned as racist, sexist, and biologically determinist.64 Taking on the Harvard XYY study in 1975, SFP charged the study’s lead scientists with serious ethical violations and methodological oversights. The Harvard study allegedly acquired subjects by providing an open-ended consent form to expectant mothers while they were in labor. The study failed to include controls (non-XYY children would not be tracked alongside the XYY subjects). It also dropped the double-blind protocol for individuals identifi ed as XYY. As SFP argued, this created the possible scenario of a self-fulfi lling prophecy. Parents informed of a child’s “high-risk” status may change their behavior toward the child; in turn, XYY boys might meet their parents’ worries with aggressive and acting-out behavior. Parents would then report this behavior to research- ers, creating a feedback loop of confi rmation. If this were to occur, it would seriously undermine the study’s fi ndings by making it diffi cult, if not impossible, to untangle the effects of an extra Y from other fac- tors. SFP argued that the Harvard study did not possess the rigor and scientifi c merit necessary to justify the study’s risks. These risks included the stigmatization of XYY boys, who were too young to consent to the research themselves, by identifying them with the aggressive supermale stereotype. SFP’s campaign, and the public uproar it created, brought the Harvard study to an end in 1975, cutting the last thread of the XYY the- ory’s scientifi c credibility and effectively ending institutional support for future XYY research.
The history of research into the Y chromosome and aggression re- mains a sore subject for many who were involved. Jacobs perceived the
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end of XYY research as purely a case of censorship by the academic left. As Jacobs said in her 1982 address:
[XYY] should have provided a useful, objective tool in the rational
study of human behavior. Instead it aroused fi erce and acrimonious
controversy that resulted, at least in the United States, in the ces-
sation of virtually all research aimed at objectively identifying sex
chromosomally abnormal individuals and understanding the effect
of the additional chromosome on their development and behavior.
Why did this happen, and can we, with hindsight, try to insure that
such an episode is never again allowed to sully human genetics?65
To this day, Jacobs remains convinced that there must be an association between the Y and aggression, stating in a 2006 interview: “And they try to tell me the Y has nothing to do with it. Absurd!”66
Some researchers concluded (and remain convinced to this day) that while an XYY syndrome had not been proven, it also had not been defi ni- tively disproved. The question could simply not be adequately studied, ei- ther because of present methodological limitations or the political climate. Exemplary is one of the last scientifi c commentaries on XYY, published in 1978. The authors reiterate the overrepresentation of XYYs in criminal in- stitutions, concluding vaguely that “since it is probable that there is con- siderable variability in the phenotypic development of XYY males, it is inappropriate to allude to an XYY syndrome.”67 Rather than denying an association between XYY and aggression, the authors hedge, instead label- ing the problem infeasible to study: “Since we lack an adequate system for classifying human aggressive behaviors and determining the base rates for different aggressive behaviors in the background population, we can- not state defi nitely whether there is an increase in aggressive behavior associated with this genotype.”68 The paper rebukes neither the crude model of genetic control of behavior nor the doubling hypothesis that underpinned the XYY theory. The view that there is still more to be explored in the relation- ship between the Y, aggression, and masculinity, was a not- uncommon understanding of the outcome of the XYY studies among members of the genetics community, even as XYY studies came to an end.
The XYY affair, along with Jensen’s infl ammatory race and IQ claims, left an indelible mark on the course of genetic science, derailing the emer- gent fi eld of behavioral genetics. Many geneticists turned away from the new project of behavioral genetics in response to the poor science and unsavory overstatements of the XYY “supermale” syndrome and Jensen’s race and IQ claims—two humiliating episodes in the history of behav-
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A Chromosome for Maleness 99
ioral genetics that remain forever paired in the minds of many. Cases such as the supposed XYY supermale so tarnished behavioral genetics’ reputation that it would be decades before the fi eld would emerge from the shadows. Chromosomal correlations with human behavior were off the table. As Robert Michels, professor of psychiatry at Cornell Medical School, stated of the XYY dust-up:
the real cost of all this is that I will tell every young psychiatrist or
physician or medical student wanting to do research on anything of
social relevance to recognize that it is immensely expensive in terms
of time and personal career because there are a lot of people in the
world who are going to bother you if you do it. It would really make
sense . . . to review whether there is something you can’t do in bean
metabolism or some kind of pigeon behavior because it is safer to
work that way in our present society.69
Indeed, by the late 1970s, research was trending toward molecular ap- proaches to genetics. Human behavior research on the Y chromosome did not present a testable, causal-mechanistic hypothesis and rigorous experimental system in the way that molecular approaches emerging in medical research or model organism biology could now offer. The com- ments of MIT biologist Jonathan King, one of the principal critics of the Harvard XYY study, make clear the role that this normative shift toward the molecular and the mechanistic played in the demise of XYY studies:
Our objection was to the attempt to link the XYY chromosome to
abnormal social behavior in very young children. . . . That was our
critique. If someone says to me, I am interested in the way that the
mitotic spindle forms in a cell that has an extra Y chromosome, fi ne.
If someone says to me, I am interested in what happens to women’s
ovaries or men’s seminiferous tubules that causes chromosome
damage, fi ne. . . . If someone said to me I want to look at the level
of histone biosynthesis in nuclei in XYY males, I might say yes. If
someone said I want to look at the relationship between XYY and
the frequency of temper tantrums, I do not know. I would probably
suspect that it lacks a valid scientifi c or medical foundation.70
In the face of attacks and empirical dead ends, XYY researchers would follow King’s lead. They would indeed retreat to “molecular analysis” of the Y chromosome rather than attempting to correlate karyotypes and human behaviors. Yet, as we shall see, even as the association between
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the Y and aggression was discredited, the model of the Y as the “chromo- some for maleness” marched forward, unexamined.
FROM XYY TO THE Y CHROMOSOME
Today it is common for sex chromosome geneticists to distance them- selves from XYY studies. In the 2003 Nature paper announcing the suc- cessful sequencing of the human Y chromosome, for example, project leader and MIT scientist David Page positioned the event as the reversal of a century of prescientifi c dogma about the Y chromosome.71 According to Page, prior to molecular analysis, biologists assumed that the Y was a “genetic wasteland” involved in no processes other than testes determi- nation. Beginning in the mid-1980s, Page said, geneticists reversed this view by bringing “recombinant DNA and genomic technologies to the Y chromosome, culminating in molecularly based conclusions about its genes.”72 The result, Page claimed, was a new model of the Y chromosome as gene-rich and specialized for maleness. This genealogy of Y chromo- some research conspicuously erases the era of Y chromosome research in the 1960s and 1970s.
XYY studies were high-profi le, mainstream cytogenetic research that represented the primary work on the human Y chromosome for two dec- ades. XYY spurred interest in the gene content and natural history of the Y, technologically and model-theoretically prepared the ground for future Y chromosome research, and rallied researchers and resources to the study of the Y. XYY research also helped to cement a working model of the Y chromosome as the chromosome for maleness that, as chapters 7 and 8 will demonstrate, remained extremely infl uential in the coming decades.
The presence of XYY as a reference point and instigating research model for understanding the genetics of the Y chromosome is evident in the primary literature, even after the XYY supermale theory was eclipsed. A 1975 Nature article on the mouse Y chromosome, for example, referred to “the XYY karyotype in man” as part of “a growing body of evidence for the involvement of the Y chromosome in the inheritance of particular characteristics.”73 In 1976 in the same journal, researchers at Johns Hop- kins reported the use of cells from XYY males in an experimental system to locate and validate the existence of Y-specifi c genes.74 They argued that the Y chromosome is made up of male-specifi c sequences, as opposed to only material that also appears in duplicate on the X. The authors con- cluded that “correlating the presence of these sequences with the various
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A Chromosome for Maleness 101
phenotypes associated with particular qualitative abnormalities of the Y chromosome” may help reveal its male-specifi c function.75
XYY studies also led to the development of cytogenetic technologies for studying the Y chromosome. A 1970 Nature editorial noted the “fever of excitement” incited by a new staining test that “makes part of the hu- man Y chromosome fl uoresce particularly brightly.” The editors wrote, “this is an important time saver for those engaged in screening human populations for XYY males, the possessors of an extra Y chromosome who tend, as adults, to be found in prisons slightly more often than it seems they should be.”76 These new techniques, crucial to late 1970s and early 1980s Y chromosome studies, were developed through intensive research on the XYY supermale.
XYY research contributed to substantive and lasting lines of research on the functional genetics of the Y chromosome. As Reed Pyeritz, a bi- ologist at Johns Hopkins, would state in a 1980 public forum on XYY research:
Molecular geneticists are devoting much effort these days to map-
ping human chromosomes. . . . The Y chromosome is a unique chro-
mosome. It contains certain DNA sequences which are repetitious
and which have been mapped to the Y chromosome; XYY cells have
actually been used in this research to prove that the DNA sequences
are Y-specifi c. In other words, men with the XYY karyotype have
twice as much of this DNA. These are the sorts of molecular and
biological applications of knowledge about XYY that have clinical
applications and potential value.77
XYY studies are woven into the history of Y chromosome research in ways that are at once instrumental and grounded in a conceptual under- standing of the Y as the chromosome for maleness.
As research shifted from XYY to genetic analysis of the “normal” Y, a model of the Y as gene-rich, rather than inert, and specialized for “male- ness,” not just the testes-determining gene, continued to motivate re- searchers. By the early 1980s, research on aggression in XYY males gave way to studies of Y chromosome polymorphisms and to structural analy- sis of the Y and, by the mid-1980s, to a search for sex-determining, fertil- ity, and other male-specifi c genes on the Y. While the association between Y and aggression had taken a hit with the decline of the XYY hypothesis, the concept of the Y as the biological kernel of maleness survived.
In noting these connections between XYY research and later molecu-
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lar and genomic studies of the Y chromosome, I do not mean to tar to- day’s Y chromosome research with the same blatant methodological er- rors that characterized XYY studies. Rather, the aim is to document how assumptions about the Y as the chromosome for maleness were formed through, and in relation to, historically specifi c scientifi c research agen- das and gender politics. Neglecting the role that the gendered assump- tion that the Y is the chromosome for maleness played in the XYY epi- sode, researchers today run the risk of not fully embracing its cautionary lessons.
9
The widespread idea of the Y as the chromosome for “maleness” owes its origins to XYY supermale theories of the 1960s and 1970s. While there had been speculation about the possibility of some male traits on the Y chromosome prior to the 1960s (see chapter 4), the XYY episode is when the conviction that the Y represents the genetic essence of male- ness fi rst entered human genetics. This conviction played a central part in the notorious methodological errors and biases that characterized XYY research. The notion of the Y as the “chromosome for maleness” remains strongly embedded in popular and scientifi c discourse today—evidence of the abiding appeal of the idea of a simple gender binary, writ molecu- lar in the human genome. The lasting contribution of the scientifi c char- acterization of double-Y individuals as bigger, more aggressive, and more sexual males would be to cement and amplify the association between the single Y and maleness.
Richardson, S. S. (2013). Sex itself : The search for male and female in the human genome. University of Chicago Press. Created from ucsd on 2023-10-14 20:13:57.
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