Are identical twins really identical?

 

Sibling similarity in personality for monozygotic twins, dizygotic twins, and adoptees (Wikicommons)

 

 

Monozygotic and dizygotic twins who were separated early in life and reared apart (MZA and DZA twin pairs) are a fascinating experiment of nature. They also provide the simplest and most powerful method for disentangling the influence of environmental and genetic factors on human characteristics. (Bouchard et al. 1990)

 

Monozygotic twins are identical twins. They develop from a single fertilized egg and are assumed to be genetically identical. Any differences between them in mind or behavior must therefore have an environmental cause. Of course, "environmental cause" does not mean only things like diet, upbringing, education, or parental help with homework. It can also mean accidents during pregnancy or childbirth.

 

But are monozygotic twins really identical? Monozygotic twins begin to go their own ways long after the zygote has made its first division. It's actually around a week later that they begin to develop separately, when the zygote has already divided several times to form a mass of about sixteen cells. During that time, mutations may have occurred in one cell lineage or another, and not all of those mutations will be inherited by both twins. A twin may in fact develop from a single lineage or several lineages within the cell mass. The two twins may thus be genetically different.

 

Jónsson et al. (2021) have quantified these genetic differences between twins. They examined the body tissues of adult twins, specifically one sample from adipose tissue, 204 samples from buccal tissue, and 563 blood samples.  On average, one of the twins had 14 postzygotic mutations that were not present in the other. There was, however, considerable variability: 39 twin pairs differed at more than 100 loci, whereas 38 pairs did not differ at all.

 

Germ cells develop from a subset of cell lineages very early in embryonic development, and it is possible to see how twins differ genetically in their germ lines by looking at their offspring. In this case, there was a difference of 5.2 mutations between twins. Again, there was considerable variability, ranging from a minimum of no mutations at all in 207 offspring to a maximum of 8 mutations in 3 offspring.

 

If monozygotic twins are not genetically identical, we will have to revise upwards our estimates of the relative importance of nature versus nurture in different human traits:

 

Phenotypic discordance between monozygotic twins has generally been attributed to the environment. This assumes that the contribution of mutations that separate monozygotic twins is negligible; however, for some diseases such as autism and other developmental disorders, a substantial component is due to de novo mutations. Our analysis demonstrates that in 15% of monozygotic twins a substantial number of mutations are specific to one twin but not the other. This discordance suggests that in most heritability models the contribution of sequence variation to the pathogenesis of diseases with an appreciable mutational component is underestimated. (Jónsson et al. 2021)

 

In particular, we will have to revise upwards our estimates of the genetic component of intelligence, such as the 70% estimate offered by Bouchard et al. (1990):

 

Since 1979, a continuing study of monozygotic and dizygotic twins, separated in infancy and reared apart, has subjected more than 100 sets of reared-apart twins or triplets to a week of intensive psychological and physiological assessment. Like the prior, smaller studies of monozygotic twins reared apart, about 70% of the variance in IQ was found to be associated with genetic variation. On multiple measures of personality and temperament, occupational and leisure-time interests, and social attitudes, monozygotic twins reared apart are about as similar as are monozygotic twins reared together.

 

Or the 41% to 66% estimate offered by Haworth et al. (2020):

 

Although common sense suggests that environmental influences increasingly account for individual differences in behavior as experiences accumulate during the course of life, this hypothesis has not previously been tested, in part because of the large sample sizes needed for an adequately powered analysis. Here we show for general cognitive ability that, to the contrary, genetic influence increases with age. The heritability of general cognitive ability increases significantly and linearly from 41% in childhood (9 years) to 55% in adolescence (12 years) and to 66% in young adulthood (17 years) in a sample of 11 000 pairs of twins from four countries, a larger sample than all previous studies combined.

 

My criticisms

 

Why focus on germline differences?

 

I have two criticisms of the study by Jónsson et al. (2020). First, their abstract highlights the median of 5.2 mutational differences in the germline, and not the larger median of 14 mutational differences in somatic tissues.

 

Here we show that monozygotic twins differ on average by 5.2 early developmental mutations and that approximately 15% of monozygotic twins have a substantial number of these early developmental mutations specific to one of them. (Jónsson et al. 2021)

 

Yes, "heritability" refers to genes that are passed on to the next generation, but most twin studies don't include the offspring of twins. The researchers simply examine pairs of monozygotic twins and see how they differ. Any differences would therefore reflect differences in somatic tissues and not the germline, or at least not solely the germline.

 

Undoubtedly, some of the somatic mutations occurred later in development, but they would still be relevant for any study on adult monozygotic twins.

 

Do these differences really make a difference?

 

We estimate the genetic component of a mental or behavioral trait by comparing monozygotic and dizygotic twins, i.e., identical and fraternal twins. A difference between monozygotic twins is assumed to be 100% environmental, and a difference between dizygotic twins is assumed to be partly environmental and partly genetic. Therefore, we can estimate the genetic component by subtracting one from the other, right?

 

This is where the study by Jónsson et al. (2021) comes in. They argue that the genetic component is always underestimated because some of the difference between monozygotic twins is also genetic. But is that additional genetic difference large enough to make a difference? If monozygotic twins differ from each other, on average, at 14 loci, and dizygotic twins differ from each other, on average, at 1400 loci, we might as well assume that monozygotic twins are genetically identical. Any upward revision of the heritability estimate would be slight.

 

Of course, the key lies in the words "on average." Some of the twins in this study differed at more than 100 loci. More importantly, around 15% of the twins had a substantial number of "near-constitutional" mutations, i.e., absent from one twin and present in almost all the tissues of the other. In those cases, we could see big differences in development between the two.

 

It's difficult to say without a point of comparison. In other words, the same kind of study should be done on dizygotic twins. How much more variable are they genetically?

 

 

References

 

Bouchard Jr., T.J., D.T. Lykken, M. McGue, N.L. Segal, and A. Tellegen. (1990). Sources of human psychological differences: the Minnesota Study of Twins Reared Apart. Science 250(4978): 223-228. https://doi.org/10.1126/science.2218526

 

Haworth, C.M.A., M. J. Wright, M. Luciano, N.G. Martin, E.J.C. de Geus, et al. (2010). The heritability of general cognitive ability increases linearly from childhood to young adulthood. Molecular Psychiatry 15: 1112-1120. https://doi.org/10.1038/mp.2009.55

 

Jónsson, H., E. Magnusdottir, H.P. Eggertsson, O.A. Stefansson, G.A. Arnadottir, et al. (2021). Differences between germline genomes of monozygotic twins. Nature Genetics 53: 27-34 (2021). https://doi.org/10.1038/s41588-020-00755-1

The fellowship instinct

Grace Fellowship Assembly of God, Bloomington, Indiana – Fellowship is what primarily draws people to religion (Wikicommons - Vmenkov).

 

Religiosity is moderately heritable—25 to 45% according to twin studies (Bouchard, 2004; Lewis and Bates, 2013). These figures are of course underestimates, since any noise in the data gets classified as ‘non-genetic’ variability. So the estimates would be higher if we could measure religiosity better.

But what does it mean to be religious? Does it mean adhering to a single organized religion with a clergy, a place of worship, and a standardized creed? This definition works fairly well in the Christian and Muslim worlds, but not so well farther afield. In East Asia, people often have more than one faith tradition: “If one religion is good, two are better.” Moreover, 'religion' has never controlled East Asian societies to the extent that Christianity and Islam have controlled theirs, as Francis Fukuyama notes in The Origins of Political Order. This word becomes even more problematic in simple societies. Did hunter-gatherers have religion? If we take the example of the Inuit, they believed in spirits of various kinds, but those spirits were indifferent to humans and their concerns, being not at all like the fellow in the Christmas jingle: 

He sees you when you're sleeping.

He knows when you're awake.
He knows if you've been bad or good,
So be good for goodness sake!

Simple hunter-gatherers had no idea that a moral God exists. Nor did they see morality as being absolute or universal. A human action could be good or bad, depending on who was doing what to whom. Morality could not be separated from kinship. Your first moral obligation was to yourself, then to your family, then to your close kin. Beyond, who cares?

So what exactly is the heritable component of religiosity? Or should we say components? These questions were addressed by a recent twin study, which concluded that "religiosity is a biologically complex construct, with distinct heritable components" (Lewis and Bates, 2013). The most important one seems to be 'community integration,' which is the desire to be among people who befriend each other and help each other on a regular basis. Much research shows that religious people have stronger social needs than the rest of us, and they tend to lose interest in religion when such needs are no longer met. When former Methodist church members were asked why they left their church, the most common response was their failure to feel accepted, loved, or wanted by others in the congregation (Lewis and Bates, 2013).

The second most important component seems to be 'existential certainty'—belief in a controlling God who will ultimately take care of everything. Belief in divine control reduces anxiety and actually increases one's sense of personal control. As such, it provides "an epistemic buffer from a range of factors such as unpredictability, instability, and concerns over mortality that exist in this world."

In sum, this study found that community integration accounts for 45% of innate religiosity and existential certainty for 11%. These two components represent most of the genetic variability.

Just one thing. The study was done with a sample of Americans who were 85.1% Christian, the rest being mostly atheist, agnostic, or ''no religious preference." Would the results have been similar with participants from the Middle East, Africa, or East Asia?

I don’t think so. Religiosity, by its very nature, should be very sensitive to gene-culture coevolution. It's moderately heritable and serves different purposes in different cultural environments. Any one religion will favor its own ways of being and acting, and people who conform will do better than those who don’t. Thus, over successive generations, the gene pool of believers will become characterized by certain predispositions, personality traits, and other heritable aspects of mental makeup. These characteristics will tend to persist even if the believers cease to believe and become secularized.

This point is made by the authors, albeit indirectly. On the one hand, a community of believers will modify their religion to suit their social and existential needs:

[...] religion per-sé may not be the sole organization or system able to fill the niche created by human needs for community and existential meaning. The succession, displacement, and evolution of religions can be viewed in this light as the shaping of religious systems by their adherents to maximize the extent to which their needs are met.

On the other hand, a religion will modify its community of believers by favoring the survival of those with the "right" mindset and by removing those with the “wrong” mindset:

[...] this ''exchangeable goods'' notion of religion may fail to acknowledge the tight fit between religious belief and human psychology: ''religious practices and rituals co-evolved with religiously inclined minds, so that they now fit together extremely well."

In short, Man has made religion in his own image, but religion has returned the favor. In a very real sense, it has made us who we are.

References 

Bouchard, T. J. Jr., (2004). Genetic influence on human psychological traits: A survey. Current Directions in Psychological Science, 13, 148-151.

https://www.researchgate.net/profile/Thomas_Bouchard2/publication/241644869_Genetic_Influence_on_Human_Psychological_TraitsA_Survey/links/00b7d524a1ab5b5f9d000000.pdf 

Lewis, G.J. and T.C. Bates. (2013). Common genetic influences underpin religiosity, community integration, and existential uncertainty, Journal of Research in Personality, 47, 398-405.

http://www.aging.wisc.edu/midus/findings/pdfs/1268.pdf

Compliance with moral norms: a partly heritable trait?

 

Election poster from the 1930s for Sweden’s Social Democratic Party (source). Is the welfare state more workable if the population is more predisposed to obey moral norms?

 

Do we differ genetically in our ability, or willingness, to comply with moral norms? Please note: I'm talking about compliance. The norms themselves can vary greatly from one historical period to another and from one society to another.

Apparently some people are more norm-compliant than others. This is the conclusion of a recent twin study from Sweden (Loewen et al., 2013). A total of 2,273 individuals from twin pairs were queried about the acceptability of four dishonest behaviors: claiming sick benefits while healthy (1.4% thought it totally or fairly acceptable), avoiding paying for public transit (2.8%), avoiding paying taxes (9.7%), and accepting bribes on the job (6.4%).

How heritable were the responses to the above questions? The heritabilities were as follows: 

Claiming sick benefits while healthy - 42.5%

Avoiding paying for public transit - 42.3%
Avoiding paying taxes - 26.3%
Accepting bribes on the job - 39.7%

Do these results indicate a specific predisposition to obey moral norms? Or is the genetic influence something more general, like religiosity or risk-taking, both of which are known to be partly heritable? To answer this question, the authors ran correlations with other factors:

Significant correlations were exhibited for age (r=.10, p=.00), sex (r=.12, p=.00), religiosity (r=.06, p=.00), preferences for risk (r=-.09, p=.00) and fairness (r=-.10, p=.00), locus of control (r=-.03, p=.01), and charitable giving (r=.09, p=.00). However, these significant correlations were relatively weak, suggesting that our measure is not merely standing in for these demographic and psychological differences between individuals. There were no significant correlations with behavioral inhibition (r=-.00, p=.81) or volunteering (r=.01, p=.29). (Loewen et al., 2013)

The jury is still out, but it looks like compliance with moral norms has a specific heritable component.

 

Population differences

Does this heritable component vary from one population to another, just as it seems to vary from one individual to another? The authors have little to say, other than the following:

Replication in other countries should occur, as the exact role and extent of genetic and common environment-influence could change in different national and cultural contexts. Such a multi-country approach could thus offer some clues on the generalizability of our findings. (Loewen et al., 2013)

Swedes seem to be better than most people at obeying moral norms. Only 1.4% think it acceptable to claim sick benefits while healthy! Maybe that's why they've been so successful at creating a welfare state. So few of them want to be free riders on the gravy train:

Gunnar and Alva Myrdal were the intellectual parents of the Swedish welfare state. In the 1930s they came to believe that Sweden was the ideal candidate for a cradle-to-grave welfare state. First of all, the Swedish population was small and homogeneous, with high levels of trust in one another and the government. Because Sweden never had a feudal period and the government always allowed some sort of popular representation, the land-owning farmers got used to seeing authorities and the government more as part of their own people and society than as external enemies. Second, the civil service was efficient and free from corruption. Third, a Protestant work-ethic—and strong social pressures from family, friends and neighbors to conform to that ethic—meant that people would work hard, even as taxes rose and social assistance expanded. Finally, that work would be very productive, given Sweden´s well-educated population and strong export sector. (Norberg, 2006)

This is not how most of the world works. While studying in Russia, I noticed that the typical Russian feels a strong sense of moral responsibility toward immediate family and longstanding friends, more so than we in the West. Beyond that charmed circle, however, the general feeling seems to be distrust, wariness, or indifference. There was little of the spontaneous willingness to help strangers that I had taken for granted back home. People had the same sense of right and wrong, but this moral universe was strongly centered on their own families.

In sociology, the term is amoral familialism. Family is everything and society is nothing, or almost nothing. It was coined by American sociologist Edward Banfield:

In 1958, Banfield, with the assistance of his wife, Laura, published The Moral Basis of a Backward Society, in which they explained why a region in southern Italy was poor. The reason, they said, was not government neglect or poor education, but culture. People in this area were reluctant to cooperate outside of their families. This kind of "amoral familialism," as they called it, was the result of a high death rate, a defective system of owning land, and the absence of extended families. By contrast, in an equally forbidding part of southern Utah, the residents were engaged in a variety of associations, each busily involved in improving the life of the community. In southern Italy, people did not cooperate; in southern Utah, they scarcely did anything else. (Banfield, 2003, p. viii)

 

Where did Western societies get this desire to treat family and non-family the same way? To some extent, it seems to be a longstanding trait. English historian Alan Macfarlane sees a tendency toward weaker kinship ties that goes back at least to the 13th century. Children had no automatic rights to the family property. Parents could leave their property to whomever they liked and disinherit their children if they so wished (Macfarlane, 2012).

Indeed, Macfarlane argues that "Weber's de-familization of society" was already well advanced in Anglo-Saxon times (Macfarlane, 1992, pp. 173-174). This picture of relatively weak kinship ties is consistent with the Western European marriage pattern. If we look at European societies west of a line running from Trieste to St. Petersburg, we find that certain cultural traits predominate:

- relatively late marriage for men and women

- many people who never marry
- neolocality (children leave the family household to form new households)
- high circulation of non-kin among different households (typically young people sent out as servants) (Hajnal, 1965; see also hbd* chick)

Again, these characteristics go back at least to the 13th century and perhaps much farther back (Seccombe, 1992, p. 94).

Historians associate this model of society with the rise of the market economy. In other words, reciprocal kinship obligations were replaced with monetized economic obligations, and this process in turn led to a broader-based morality that applied to everyone equally. In reality, the arrow of causation seems to have been the reverse. Certain societies, notably those of northwestern Europe, were pre-adapted to the market economy and thus better able to exploit its possibilities when it began to take off in the late Middle Ages. The expansion of the market economy and, later, that of the welfare state were thus made possible by certain pre-existing cultural and possibly genetic characteristics, i.e., weaker kinship ties and a corresponding extension of morality from the familial level to the societal level.

 

References

Banfield, E.C. (2003). Political Influence, New Brunswick (N.J.): Transaction Pub.

Hajnal, John (1965). European marriage pattern in historical perspective. In D.V. Glass and D.E.C. Eversley. Population in History. Arnold, London. 

Loewen, P.J., C.T. Dawes, N. Mazar, M. Johannesson, P. Keollinger, and P.K.E. Magnusson. (2013). The heritability of moral standards for everyday dishonesty, Journal of Economic Behavior & Organization, 93, 363-366.

https://files.nyu.edu/ctd1/public/Moral.pdf  

Macfarlane, A. (1992). On individualism, Proceedings of the British Academy, 82, 171-199.

http://www.alanmacfarlane.com/TEXTS/On_Individualism.pdf  

Macfarlane, A. (2012). The invention of the modern world. Chapter 8: Family, friendship and population, The Fortnightly Review, Spring-Summer serial

http://fortnightlyreview.co.uk/2012/07/invention-8/  

Norberg, J. (2006). Swedish Models, June 1, The National Interest.

http://www.johannorberg.net/?page=articles&articleid=151  

Seccombe, W. (1992). A Millennium of Family Change. Feudalism to Capitalism in Northwestern Europe, London: Verso.

 

Where do those tensions come from?

 

Home sweet home in the Scottish borderlands. This was one of the last regions of Britain to be pacified and brought under State control. People lived in fortified homes where the second floor could be reached only by an external ladder that could be pulled up. The stone walls were up to 3 feet thick. (source – photo owned by Les Hull)

I first went to elementary school in a largely English Canadian neighborhood of Scarborough. Schoolyard fights were only occasional, and there was almost always a good reason. My family then moved to a largely Scotch-Irish town in central Ontario. There, the schoolyard fights were a daily occurrence, and they seemed to happen for no reason at all. I eventually found out the reason … something to do with “respect” or rather the lack of it.

We like to think that people everywhere respond to situations more or less as we do. If the response is anger—red boiling anger that can kill—we assume there must be a very good reason. Otherwise, the person wouldn’t be so angry.

Hence the puzzlement over the Boston bombers. What drove them to such an act? Had they been treated badly? This was the conclusion reached by Justin Trudeau, the recently elected leader of the Liberal Party of Canada:

But there is no question that this happened because there is someone who feels completely excluded. Completely at war with innocents. At war with a society. And our approach has to be, where do those tensions come from? (The National, 2013)

Actually, the Tsarnaev brothers were hardly excluded from American society. Tamerlan married the daughter of a well-off American family and lived in their spacious home. Sure, if you look hard enough, you may find evidence of exclusion. There must have been slights and indifference, perhaps jokes about his first name, but such things don’t cause normal people to kill.

“Normal” is a relative term. In other societies, people do kill for apparently trifling reasons. In Les damnés de la Terre, Frantz Fanon discusses male violence in Algeria, particularly the lack of restraint and the apparently trivial motives:

Autopsies undeniably establish this fact: the killer gives the impression he wanted to kill an incalculable number of times given the equal deadliness of the wounds inflicted.

[…] Very often the magistrates and police officers are stunned by the motives for the murder: a gesture, an allusion, an ambiguous remark, a quarrel over the ownership of an olive tree or an animal that has strayed a few feet. The search for the cause, which is expected to justify and pin down the murder, in some cases a double or triple murder, turns up a hopelessly trivial motive. Hence the frequent impression that the community is hiding the real motives. (Fanon, 2004, p. 222)

This behavioral pattern begins early in life. Parents seek not to suppress it but to channel it in the right direction, i.e., defense of the family:

In Algerian society for example, children are raised according to their sex. A boy usually receives an authoritarian and severe type of upbringing that will prepare him to become aware of the responsibilities that await him in adulthood, notably responsibility for his family and for the elderly. This is why a mother will allow her son to fight in the street and will scarcely be alarmed if the boy has a fall or if she sees a bruise. The boy of an Algerian family is accustomed from an early age to being hit hard without whimpering too much. People orient him more toward combat sports and group games in order to arm him with courage and endurance—virtues deemed to be manly. (Assous, 2005)

This pattern of behavioral development doesn’t differ completely from my own. The difference is largely one of degree. But there’s also a difference in kind: the violent male as an independent actor who fights for himself and his immediate family. For “normal” boys in Western society, male violence is legitimate only when done under orders for much larger entities: the home team, the police, the country, NATO … Everywhere else, it is evil, criminal, and pathological.

This schizophrenic attitude to violence was the subject of the Milgram experiment. You’ve probably heard of it. Assistants are told to administer ever stronger electric shocks if a subject fails on a learning task. About 65% of the assistants—the real subjects of the experiment—will increase the shock intensity up to the top end of the scale, even when the pseudo-subject pleads for cessation. Yet the same assistants act very differently if the decision is theirs. Only 1.4% of them will, on their own initiative, increase the shock intensity up to the top end of the scale (Milgram, 1974)

You may not have heard, however, that this finding holds true only for societies like our own. When the Milgram experiment was done with Jordanian assistants, they were just as willing as Americans to inflict pain under orders (62.5%). But they were more willing than Americans to inflict pain when no orders were given, with 12.5% of them delivering shocks right up to the top end of the scale (Shanab & Yahya, 1978).

How would Chechens have responded in the same situation? Or Algerians? Or Scotch-Irish? Male violence has long been viewed differently in different societies. In our own, it is stigmatized, except when done “under orders” by soldiers or the police. Some societies, however, had no police or army until recent times. Every adult male was expected to use violence to defend himself and his family. Yes, you could go to a law court to settle your differences with someone. But even if the court ruled in your favor, the sentence still had to be enforced by you, your brothers, and other male family members. That’s the way things were done. For millennia and millennia.

Gene-culture co-evolution

Humans differ from other animals in that we create a large part of our environment. We adapt not only to a physical environment of climate, landscape, vegetation, and wildlife but also to a cultural environment of our making: codified laws, behavioral norms, religious beliefs, social and political systems, and so on. We shape our environment, and this environment shapes us. To be more precise, it selects the kind of individuals who can live in it.

Initially, all adult males everywhere had to defend themselves and their families, not by paying taxes but by getting their hands bloody. This situation changed with the rise of the State. In other words, some powerful men became so powerful that they could impose a monopoly on the use of violence. Only they or their underlings could use it. Male violence had been “nationalized” and could be used only if ordered by the State or in narrowly defined situations of self-defense.

In this new pacified environment, the violent male went from hero to zero. He became a criminal and was treated accordingly. Society now favored the peace-loving man who got ahead through work or trade. This process has been described for England and other parts of Western Europe by several academics, like Gregory Clark. With the establishment of strong States toward the end of the Dark Ages, and a subsequent pacification of social relations, the incidence of violence declined steadily. Violent predispositions were steadily removed from the population, either through the actual execution of violent individuals or through their marginalization and lower reproductive success. The meek thus inherited the earth (see previous post).

Or rather a portion of it. In some parts of the earth, particularly remote mountainous areas, State control came very late. These are societies in the earliest stages of pacification. Male violence is a daily reality, which the State can only contain at best. Such is life in Chechnya … and elsewhere.

Genetics of male violence  

But is such gene-culture co-evolution possible? How susceptible is male violence to the forces of natural selection? Are some men more predisposed to violence than others? Is this a heritable trait, or something that men pick up from their peers?

A meta-analysis of twin and adoption studies estimated a heritability of 40% for aggressive behavior (Rhee & Waldman, 2002). A later twin study found a heritability of 96%, where the subjects were 9-10 year-olds of diverse ethnic backgrounds (Baker et al., 2007). This higher figure reflected the narrow age range and the use of a panel of evaluators to rate each subject. In the latest twin study, the heritability was 40% when the twins had different evaluators and 69% when they had the same evaluator. By comparison, many of us accept that homosexuality is inborn even though the heritability of that behavior is much lower: perhaps 34-39% for gays and 18-19% for lesbians (Wikipedia, 2013).

The actual neural basis remains to be sketched out. Perhaps a greater predisposition to violence simply reflects stronger impulsivity and weaker internal constraints on behavior (Niv et al., 2012). Or perhaps there is a lower threshold specifically for expression of violence. Or perhaps ideation of violence comes easier. Or perhaps the consequences of a violent act trigger feelings of pleasure. Frantz Fanon noted that the violent male seems to feel pleasure at the sight of blood. He needs to sense its warmth and even bathe in it. There is in fact an extensive medical literature about “abnormal” individuals who feel pleasure at the sight of blood and even wish to feel and taste it, whereas “normal” individuals feel disgust and often faint (Vanden Berghe & Kelly, 1964). Again, words like “normal” and “abnormal” are relative …

All of this may seem incomprehensible to nice folks like Justin Trudeau. Surely, no one in his right mind would enjoy violence. There must be another reason for such horrors. A good reason. A reason that would make sense to nice folks. Because, deep down, we’re all nice folks, aren’t we?

References

Assous, A. (2005). L’impact de l’éducation parentale sur le développement de l’enfant, Hawwa, 3(3), 354-369.

Baker, L.A., K.C. Jacobson, A. Raine, D.I. Lozano, and S. Bezdjian (2007). Genetic and environmental bases of childhood antisocial behavior: a multi-informant twin study, Journal of Abnormal Psychology, 116, 219-235.

http://cnpru.bsd.uchicago.edu/PDFs/Baker_2007_JAP_RFAB.pdf 

Fanon, F. (2004). The Wretched of the Earth, New York: Grove Press.

Milgram, S. (1974). Obedience to Authority, New York: Harper & Row.

Niv, S., C. Tuvblad, A. Raine, P. Wang, and L.A. Baker. (2012). Heritability and longitudinal stability of impulsivity in adolescence, Behavior Genetics, 42, 378-392.

http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3351554/  

Rhee, S.H. and I.D. Waldman. (2002). Genetic and environmental influences on antisocial behavior: A meta-analysis of twin and adoption studies, Psychol Bull., 128, 490-529.

Shanab, M.E. and Yahya, K.A. (1978). A cross-cultural study of obedience, Bulletin of the Psychonomic Society, 11, 267-269.

The National. (2013). Trudeau on Boston bombings, April 17

http://www.cbc.ca/player/News/ID/2380243779/

Vanden Bergh, R.L., and J.F. Kelly. (1964). Vampirism. A review with new observations, Archives of General Psychiatry, 11, 543-547.

Wikipedia (2013). Biology and Sexual Orientation,

http://en.wikipedia.org/wiki/Biology_and_sexual_orientation

 

 

The Montreal massacre. Part II

In debating the causes of the Montreal Massacre, we must confront the psychological similarities between Marc Lépine and his father. Both seem to have had low thresholds for ideation and expression of violence. Was this quick temper passed down from father to son? Or are the similarities only fortuitous?

If these psychological characteristics had passed down from father to son, they could have done so in only one of two ways. The preferred explanation is some kind of role-model conditioning, i.e., Marc Lépine looked to his father as a model for future behavior. But this seems unlikely. Marc hated his father. He repeatedly said so and reproached his mother for not doing enough to protect him from his father’s rage. Nor did he try to renew contact with his father after his parents broke up.

We’re thus left with some kind of unconscious conditioning that occurred before the age of 7 (when his parents broke up) and then began to express itself after puberty. But this too seems unlikely. For one thing, it implies a kind of infancy determinism that is no longer widely accepted in child psychology (Harris, 1998; Kagan, 1996; Kagan, 1998). As Jerome Kagan (1996) points out:

If orphans who spent their first years in a Nazi concentration camp can become productive adults (Moskovitz, 1983) and if young children made homeless by war can learn adaptive strategies after being adopted by nurturing families (Rathbun, DeVirgilio, & Waldfogel, 1958; Winick, Meyer, & Harris, 1975), then one can question the belief that the majority of insecurely attached l-year-olds are at high risk for later psychological problems. Even the behavioral differences among animals in laboratory settings are not very stable from infancy to reproductive maturity: "The findings offer meager support for the idea that significant features of social interactions at maturity are fixed by experiences in early development" (Cairns & Hood, 1983, p. 353). This conclusion affirms a discovery, now more than 20 years old, that even the stereotyped, bizarre social behaviors of 6-month-old isolated macaques can be altered by placing them with younger female monkeys over a 26-week period (Suomi & Harlow, 1972). These facts are also in accord with data on humans. Werner and Smith (1982), who followed a large sample of children from infancy to early childhood, concluded, "As we watched these children grow from babyhood to adulthood, we could not help but respect the self-righting tendencies within them that produced normal development under all but the most persistently
adverse circumstances" (p. 159).

For another thing, children behaviorally resemble their parents even if removed from parental influence shortly after birth. When adopted children are compared with their biological parents, we see moderate to high heritability in transmission of male aggressiveness (Baker et al., 2007; Barker et al., 2009; Rhee and Waldman, 2002). Furthermore, the non-genetic factors seem largely unrelated to parental influence, being either peer pressure outside the home or developmental accidents before and after birth (Harris, 1998).

Thus, to explain the psychological similarities between Marc Lépine and his father, the likeliest cause is genetic transmission. Either that or the similarities are just fortuitous.

The latter possibility should not be ruled out. When Monique Lépine sued for divorce, Rachid Gharbi strenuously denied her claims that he had abused their son. So perhaps we’re hearing just one side of the story. Remember, these proceedings happened before the liberalization of Canada’s divorce laws. Monique had to provide evidence of abuse to get her divorce.

To find out Rachid Gharbi’s side of the story, I turned to an article by an Algerian author on the “Impact of parental upbringing on child development.” The author’s first point is that Algerian upbringing is sex-specific. In boys, violent behavior is accepted and even encouraged:

In Algerian society for example, children are raised according to their sex. A boy usually receives an authoritarian and severe type of upbringing that will prepare him to become aware of the responsibilities that await him in adulthood, notably responsibility for his family and for the elderly. This is why a mother will allow her son to fight in the street and will scarcely be alarmed if the boy has a fall or if she sees a bruise. The boy of an Algerian family is accustomed from an early age to being hit hard without whimpering too much. People orient him more toward combat sports and group games in order to arm him with courage and endurance—virtues deemed to be manly. (Assous, 2005)

The purpose of this upbringing is not to suppress male aggressiveness but rather to channel it in the right direction: loyalty to the family and to tradition:

It is true that, in Arab and Muslim culture, parents are encouraged to discipline a child and to teach him obedience and submission by first using methods of communication and patience, but in the case of rebellion and especially of non-respect of Islamic laws it is recommended to use corporal punishment (e.g., a child who does not practice prayer is reprimanded as early as 10 years of age). (Assous, 2005)

Parental control is especially problematic after puberty:

Thus, during adolescence for example, the child will become more and more difficult to control. This behavioral disorder evidently pushes the parents to display more ill treatment in their authority and the schoolteachers to be more severe. (Assous, 2005)

The author presents an analysis of this corporal punishment, on the basis of cases brought to the notice of hospital authorities:

- it is directed much more at boys than at girls, by a ratio of almost 3 to 1

- it is inflicted (in order of importance) by schoolteachers, parents, neighbors, and other relatives

- it usually involves the use of blunt, non-cutting objects: a belt, a pipe, or a wire

- it is directed (in order of importance) at the head, arms or legs, belly, and chest

- the injuries (in order of importance) are multiple fractures, bruises, burns, scratches, and bites

The author goes on to note:

In Algerian society, even today, the absolute authority of parents over their children is seldom called into question by adults if it is exercised judiciously and without apparent adverse effects, and even though it often happens that more or less serious incidents cannot be avoided by parents in the grip of an intense anger that they cannot manage to control. (Assous, 2005)

Clearly, Rachid Gharbi and Monique Lépine had different notions of how young boys should be brought up. Monique came from a cultural background where corporal punishment is a last resort and usually takes the form of spanking. The preferred form of punishment is shaming: the boy is made to realize that he has done something wrong. At that point, his sense of shame will do the rest. If the boy has no sense of shame, he is considered to be abnormal, if not mentally ill.

In contrast, Algerian parents use shaming mainly to control girls. For boys, it seems to be at best a secondary or even tertiary means of control, the main ones being the threat and use of corporal punishment.

Why is child discipline so different in Algeria? The reason seems to be that violence is much more omnipresent. The average Algerian male is more ready and willing to use violence preemptively or in self-defense. Social peace is maintained largely by an implicit balance of terror: violence is deterred by the threat of retaliation—if not by the victim, then by a male relative. Evidently, the balance cannot always be maintained...

This aspect of Algerian life is described by Frantz Fanon in Les damnés de la terre:

It’s a fact, the magistrates will tell you, that four fifths of the cases heard involve assault and battery. The crime rate in Algeria is one of the highest in the world, they claim. There are no petty delinquents. When the Algerian, and this applies to all North Africans, puts himself on the wrong side of the law, he always goes to extremes (Fanon, 2004, p. 222)

The act of violence itself shows less restraint and the precipitating causes seem banal:

Autopsies undeniably establish this fact: the killer gives the impression he wanted to kill an incalculable number of times given the equal deadliness of the wounds inflicted.

… Very often the magistrates and police officers are stunned by the motives for the murder: a gesture, an allusion, an ambiguous remark, a quarrel over the ownership of an olive tree or an animal that has strayed a few feet. The search for the cause, which is expected to justify and pin down the murder, in some cases a double or triple murder, turns up a hopelessly trivial motive. Hence the frequent impression that the community is hiding the real motives. (Fanon, 2004, p. 222)

The reason for this state of affairs ultimately goes back to the recentness of central authority in Algeria. Before the French conquest in the 19th century, each family depended on its male members to defend its interests. There were law courts, but they had no power to enforce their rulings. It was up to the aggrieved party to do the enforcement.

This situation was not unique. In fact, it was typical of all human societies and remains so in many parts of the world today. It changed only with the rise of central authority and its monopoly on the use of violence. With this change, the State put an end to the worst sort of tyranny: the daily fear of being assaulted or even killed, not by a foreign invader but by someone in your own town or village. The violent male went from hero to zero.

Initially, people complied with the new order by changing their behavior within the limits of phenotypic plasticity. The result was a more peaceful society where violent males were less often imitated, celebrated, and accommodated. This shift in the mean phenotype then contributed to a slower but similar shift in the mean genotype, by creating an environment that favored the reproduction of certain individuals at the expense of others. There was thus Baldwinian selection for individuals less predisposed to violence and more predisposed to submissiveness.

This process is described by the historical economist Gregory Clark with respect to England. Once central authority had become established, male homicide fell steadily from the twelfth century to the early nineteenth. Meanwhile, there was a parallel decline in blood sports and other forms of exhibitionist violence (cock fighting, bear and bull baiting, public executions) that nonetheless remained legal throughout this period. Clark ascribes this behavioral change to the reproductive success of upper- and middle-class individuals who differed statistically in their predispositions from the much larger lower class, including predispositions to violence. Although initially a small minority in medieval England, such individuals grew in number and their descendants gradually replaced the lower class through downward mobility. By the nineteenth century, their lineages accounted for most of the English population (Clark, 2007, pp. 124-129, 182-183; Clark, 2009).

Reference

Assous, A. (2005). L’impact de l’éducation parentale sur le développement de l’enfant, Hawwa, 3(3), 354-369.

Baker, L.A., K.C. Jacobson, A. Raine, D.I. Lozano, and S. Bezdjian. (2007). Genetic and environmental bases of childhood antisocial behavior: a multi-informant twin study, Journal of Abnormal Psychology, 116, 219-235.

Barker, E.D., H. Larson, E. Viding, B. Maughan, F. Rijsdijk, N. Fontaine, and R. Plomin. (2009). Common genetic but specific environmental influences for aggressive and deceitful behaviors in preadolescent males, Journal of Psychopathology and Behavioral Assessment, 31, 299-308.

Clark, G. (2009). The indicted and the wealthy: surnames, reproductive success, genetic selection and social class in pre-industrial England, http://www.econ.ucdavis.edu/faculty/gclark/Farewell%20to%20Alms/Clark%20-Surnames.pdf

Clark, G. (2007). A Farewell to Alms. A Brief Economic History of the World, Princeton University Press, Princeton and Oxford.

Fanon, F. (2004). The Wretched of the Earth, New York: Grove Press.

Harris, J. R. (1998). The nurture assumption: Why children turn out the way they do, Free Press.

Kagan, J. (1998). Three Seductive Ideas, Cambridge, Harvard University Press.

Kagan, J. (1996). Three pleasing ideas, American Psychologist, 51, 901-908.

Rhee, S.H., and I.D. Waldman. (2002). Genetic and environmental influences on antisocial behavior: A meta-analysis of twin and adoption studies, Psychological Bulletin, 128, 490-529.

The Montreal massacre ... 20 years later

On December 6, 1989, a 25-year-old man walked into Montreal’s École polytechnique and murdered fourteen women. The event is still being debated … twenty years later.

We know the immediate cause. The murderer, Marc Lépine, felt that places like the École polytechnique were training women to take jobs that had been mainly held by men like himself. In April 1989 he had met with a university admissions officer and complained about how women were taking over the job market. Earlier still, he had spoken out to men about his dislike of feminists, career women, and women in traditionally male occupations such as the police, saying that women should remain at home and care for their families. This resentment may have been exacerbated by his inability to find a girlfriend. He was generally ill at ease around women, tending to boss them around and showing off his knowledge in front of them

For many people, the debate stops there. Marc Lépine resented women, especially ‘feminists’, and this resentment led to the Montreal massacre. For others, such resentment does not in itself explain what happened. Lépine’s personal history points to a longstanding tendency toward asociality, short-temperedness, and ideation of violent behavior, particularly after he reached puberty in the late 1970s:

Late 1970s – When his sister made fun of him for not having a girlfriend, he fantasized about her death and made a mock grave for her.

September 1981 – He applied to join the Canadian Armed Forces as an officer cadet but was rejected during the interview process because he seemed antisocial and unable to accept authority.

1982-84 – At junior college, colleagues saw him as being nervous, hyperactive, and immature.

1987 – He lost his job at a hospital because of aggressive behavior, disrespect of superiors, and carelessness in his work. He was enraged at his dismissal, and at the time described a plan to go on a murderous rampage and then commit suicide. His friends said he was unpredictable and would fly into rages when frustrated.

Some people trace this behavioral pattern to his early childhood, specifically as the son of a Catholic French-Canadian mother, Monique Lépine, and a Muslim Algerian father, Rachid Liass Gharbi. The latter’s psychological profile looks very similar to Marc Lépine’s:

Gharbi was an authoritarian, possessive and jealous man, frequently violent towards his wife and his children. Gharbi had contempt for women and believed that they were only intended to serve men. He required his wife to act as his personal secretary, slapping her if she made any errors in typing, and forcing her retype documents in spite of the cries of their toddler. He was also neglectful and abusive towards his children, particularly his son, and discouraged any tenderness, as he considered it spoiling. In 1970, following an incident in which Gharbi struck his son so hard that the marks on his face were visible a week later, his mother decided to leave. (Marc Lépine - Wikipedia)

His mother had divorced his father over the issue of abuse, which had extended to the children. Beaten by his father, Rachid Liass Gharbi, for such minor problems as singing too loudly or failing to greet him in the morning, Lépine had learned to fear him.

"He was a brutal man," Monique Lépine told the court, "who did not seem to have any control over his emotions... It was always a physical gesture, a violent gesture, and always right in the face." Monique's sister confirmed these details to the judge, although Gharbi protested that they were not true. Nevertheless, the judge awarded custody to Monique. Still, young Gamil was not free of the man until he was 7 years old, and the exposure for that long to Gharbi's temper and beliefs had a strong influence. The boy so hated him that when he was 13, he changed his name to Marc Lépine. (Ramsland, 2004)

The hypothesis here is that Gharbi exerted a profound influence on his son’s future psychological development. Some rightwing bloggers go so far as to suggest that Marc Lépine himself became a Muslim, as evidenced by the beard he grew as a young man. This is unlikely for several reasons:

– He was baptized a Roman Catholic and received no religious instruction. His mother describes him as "a confirmed atheist all his life."

– He had no contact with his father past the age of 7.

– At the age of 14, he legally changed his name from Gamil Rodrigue Liass Gharbi to Marc Lépine. This was motivated partly by hatred of his father and partly by a desire to avoid being treated as an Arab at school.

– His suicide note contains no Islamic references. In fact, his use of several Latin expressions (Ad Patres, Casus Belli, Alea Jacta Est) suggests he still felt some connection with Roman Catholicism.

– As for his beard, he grew it to cover up his acne.

O.K., so Marc Lépine was not a crypto-Muslim. But maybe he unconsciously imitated his father’s behavior. We often hear this kind of argument at trials where a violent offender is shown to have had an equally violent father. The offender should thus be judged more leniently, given his poor role-model.

In Marc Lépine’s case, this kind of argument is at the limit of credibility. Remember, Gharbi was a hated parental figure who had left Lépine’s life at the age of 7. More to the point, we see the same psychological similarity between parents and their children even when the children are taken away shortly after birth and put up for adoption:

… compared to genetic children, American adoptees have a higher overall risk of contact with mental health professionals, specifically for eating disorders, learning disabilities, personality disorders and attention deficit hyperactivity disorder … They also have lower achievement and more problems in school, abuse drugs and alcohol more, and fight with or lie to parents more than genetic children …

… Adoptees may be genetically predisposed to negative outcomes at higher rates than the general population. Genetic factors clearly contribute to alcohol and drug addiction, as well as to some mental disorders like attention deficit hyperactivity disorder and schizophrenia …. An association between nonviolent criminality has been found between European adoptees and their genetic parents … Furthermore, research with Swedish adoptees suggests 55-60% of their educational performance is explained by genetic factors, and that the number of years of school adoptees complete is significantly related to how many years their genetic mothers completed
... (Gibson, 2009).

On the specific issue of male aggressiveness, we see moderate to high heritability when adopted children are compared with their biological parents. A heritability of 40% is suggested by a meta-analysis of 51 twin and adoption studies (Rhee & Waldman, 2002). A later twin study indicates a heritability of 96%, the subjects being 9-10 year-olds from diverse ethnic backgrounds (Baker et al., 2007). This higher figure is due to the closer ages of the subjects and the use of a panel of evaluators to rate each of them. According to the latest twin study, heritability is 40% when the twins have different evaluators and 69% when they have the same evaluator (Barker et al., 2009).

This is not to say that the Montreal massacre was genetically inevitable. If Lépine had found a girlfriend, who would have put up with him, he would have probably become a man like his father but nothing more serious. The tragedy on December 6, 1989 resulted from three interacting factors: 1) a latent predisposition to violence, probably in the form of low thresholds for ideation and expression of violent behavior; 2) lack of close friends, especially female friends; and 3) an enabling ideology.

References

Baker, L.A., K.C. Jacobson, A. Raine, D.I. Lozano, and S. Bezdjian. (2007). Genetic and environmental bases of childhood antisocial behavior: a multi-informant twin study, Journal of Abnormal Psychology, 116, 219-235.

Barker, E.D., H. Larson, E. Viding, B. Maughan, F. Rijsdijk, N. Fontaine, and R. Plomin. (2009). Common genetic but specific environmental influences for aggressive and deceitful behaviors in preadolescent males, Journal of Psychopathology and Behavioral Assessment, early view.

Gibson, K. (2009). Differential parental investment in families with both adopted and genetic children, Evolution and Human Behavior, 30, 184-189.

Lépine, Monique & H. Gagné. (2008). Aftermath, Viking.

Lépine, Marc. (1989). Lettre de Marc Lépine,
http://www.philo5.com/Feminisme-Masculisme/890612%20Lettre%20de%20Marc%20Lepine.htm

Marc Lépine - Wikipedia

Ramsland, K. (2004), Gendercide – The Montreal Massacre.
http://www.trutv.com/library/crime/notorious_murders/mass/marc_lepine/10.html

Report of Coroner’s Investigation http://www.diarmani.com/Montreal_Coroners_Report.pdf

Rhee, S.H., and I.D. Waldman. (2002). Genetic and environmental influences on antisocial behavior: A meta-analysis of twin and adoption studies, Psychological Bulletin, 128, 490-529.