The New York Times Celebrates Twin Research Yet Again


In July, 2015 an article was published in the New York Times Magazine about a pair of male Colombian MZ twins (monozygotic, identical), where one member had been accidentally switched at birth with the member of another MZ pair. Each pair had grown up believing that they were a set of DZ twin pairs (dizygotic, fraternal). Because they were switched, both pairs were in fact genetically unrelated to each other. The author of “The Mixed-Up Brothers of Bogotá,” Susan Dominus, told the story of how these pairs had been switched at birth, and how they were reunited as young adults.1

This is a fascinating human interest story. However, as often happens in articles of this type, Dominus presented the human interest angle in the context of the “nature-nurture question” and the alleged scientific findings from earlier behavioral genetic twin research. Leading twin researchers are frequently called upon as experts in these types of articles—in this case behavioral geneticist Nancy Segal, who travelled to Colombia to meet and assess the twins. Dominus attempted to weave the behavioral genetic perspective into the story of the Colombian twins’ lives. The genre goes back at least to 1979, with the discovery of Jim Lewis and Jim Springer of Ohio, commonly referred to as the “Jim Twins,” who were separated at birth and were reunited at age 39.2 The Jim Twins were said to share a “spooky” set of similarities, such as the names of their wives and children, career choices, preferences for particular brands of beer and cigarettes, and favorite holiday vacation spots as teenagers. The stories of the Jim Twins and other such pairs have been told and retold ad nauseam in the mainstream media over the past four decades in support of the view that hereditary influences on human behavioral differences have a powerful impact. In fact, these stories suggest nothing of the kind.3 Dominus also mentioned the Jim Twins, who for her “seemed to have been wholly formed from conception, impervious to the effects of parenting, siblings or geography.”

Turning to studies of reared-together pairs, Dominus cited MZ-DZ twin method comparisons, where MZ pairs usually correlate much higher (resemble each other more) than same-sex DZ pairs for the behavioral characteristic in question. Like most journalists, she accepted at face value researchers’ claim that reared-together MZ-DZ comparisons are able to “tease out how much variation within a population can be attributed to heredity and how much to environment.” Also like many journalists, she failed to mention that this conclusion is based on the controversial behavioral genetic assumption that genetic and environmental influences are additive (as opposed to interactive), and that their variances can be partitioned into genetic and environmental components.4 In the process, Dominus tacitly endorsed what critics argue is the fallacious use of heritability estimates in human behavioral research.

Dominus also did not mention that twin researchers must assume that reared-together MZ and DZ twin pairs grow up experiencing the same types of environments (the twin method’s MZ-DZ “equal environment assumption,” or “EEA”), or that critics have argued for decades that this assumption is utterly false. Dominus cited a 2015 twin method meta-analysis (analysis of combined studies)5 as providing additional evidence that “any particular trait or disease in an individual is about 50 percent influenced by environment and 50 percent influenced by genes.” However, combining many individual behavioral twin studies, each misinterpreted in favor of genetics, still does not add up to a genetic finding.

In her discussion of the finding that environmental experiences can switch genes on and off “epigenetically,”6 Dominus wrote of “the myth of identical twins.” She quoted a researcher who found that some newborn twins are more similar epigenetically to an “unrelated baby” than to their MZ co-twin, but failed to mention that this finding undermines another basic assumption of twin research, which holds that MZ pairs are genetically identical to each other from conception and remain that way during their entire lives.7 The authors of a leading behavioral genetics textbook, for example, wrote that twin studies are based on “pairs of identical [MZ] twins, who are genetically identical.”8 Dominus noted that “traditional twin studies were perceived to be seeking the immutable” gene, but the discovery of epigenetic processes itself undermines the conclusions twin researchers arrived at, and continue to arrive at, on the basis of traditional twin studies. Unable or unwilling to question the controversial basic assumptions of twin research, or to highlight the arguments of twin research critics, Dominus discussed epigenetics in the context of behavioral genetic research, and implied that epigenetic discoveries were consistent with behavioral genetic findings and theories.

After Segal found that the separated Colombian MZ pairs were less alike behaviorally than she had expected, Dominus quoted her as saying, “I came away with a real respect for the effect of an extremely different environment.” It is typical of behavioral genetic tunnel vision that Segal could reach this conclusion only by observing twins, and by ignoring the obvious worldwide effects that living in extremely different environments (not to mention extremely different eras) have on human behavioral differences in general.

Historically, the Times and other mainstream (corporate) media outlets have reported on genetic and biological theories of human behavioral differences from the perspective that these influences are important, usually quoting the statements of scientists and twin researchers who promote these positions, while largely ignoring the views of their critics. The genetic determinist theories they often promote coincide with the interests of the economically and politically powerful sections of American society (including the drug companies), who finance and promote the research. These groups have an interest in focusing on biology and genetics (blaming the body), and in diverting attention from the psychological and physical damage caused by poverty, racism, child abuse, war, sexism, and many other types of trauma and oppression.9 In the United States, six corporate media companies control 90% of the information that Americans read, watch, and listen to.

In their 1988 book Manufacturing Consent, Edward S. Herman and Noam Chomsky  concluded that “the ‘societal purpose’ of the media is to inculcate and defend the economic, social, and political agenda of privileged groups that dominate the domestic society and the state.”10 To cite a current example, the Times continues to engage in what one writer characterized as “Orwellian” reporting on the current crisis in Ukraine in support of U.S. foreign policy, and continues to support the oppressive U.S.-backed Kiev “Maidan” regime.11 The article on the Colombian twins illustrates how the Times and other mainstream sources continue attempts to “manufacture consent” in the genetics of behavior area as well

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  1. Dominus, S., (2015, July 9th), The Mixed-Up Brothers of Bogotá, New York Times Magazine.
  2. For an early New York Times discussion of the “Jim Twins,” see Chen, E., (1979, December 9th), “Twins Reared Apart: A Living Lab,” New York Times Magazine, pp. 114-123.
  3. Dusek, V., (1987), Bewitching Science, Science for the People, 19, (6), 19-22;  Joseph, J., (2004), The Gene Illusion: Genetic Research in Psychiatry and Psychology under the Microscope, New York: Algora; Joseph, J., (2015), The Trouble with Twin Studies: A Reassessment of Twin Research in the Social and Behavioral Sciences, New York: Routledge
  4. For a critique of this theory, see Keller, E. F., (2010), The Mirage of a Space between Nature and Nurture, Durham, NC: Duke University Press.
  5. Polderman et al., (2015), Meta-Analysis of the Heritability of Human Traits Based on Fifty Years of Twin Studies, Nature Genetics, published online 5/18/2015. doi:10.1038/ng.3285
  6. Epigenetics is the study of how the expression of genetic characteristics is modified by environmental influences or other mechanisms without a change to the DNA sequence.
  7. Charney, E., (2012), Behavior Genetics and Postgenomics, Behavioral and Brain Sciences, 35, 331-358.  
  8. Plomin et al., (2013), Behavioral Genetics (6th ed.), New York: Worth Publishers, p. 35.
  9. See Chase, A., (1980), The Legacy of Malthus: The Social Costs of the New Scientific Racism, Urbana, IL/Chicago: University of Illinois Press (originally published in 1977).
  10. Herman, E. S., & Chomsky, N., (1988), Manufacturing Consent: The Political Economy of the Mass Media, New York: Pantheon, p. 298.
  11. With Ukrainian government complicity, far-right and ultranationalist groups have carried out massacres and assassinations of opponents, including the May 2, 2014 Odessa Massacre.


Mad in America hosts blogs by a diverse group of writers. These posts are designed to serve as a public forum for a discussion—broadly speaking—of psychiatry and its treatments. The opinions expressed are the writers’ own.


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  1. I was taken away from my foster family and sent to be experimented on with shock treatment at the age of six. This was based partly on the BS that “schizophrenia” was inherited, in my case supposedly, from my mother. (But mostly on the practice of treating foster children as easy subjects of drugging and psychiatric abuse.) So all this persistence of genetic theories about “mental illness” has a high importance to me.

    And as Jay Joseph shows, the persistence of these lies, presented as scientific facts, comes down to the profit and power of psychiatry and (nowadays) the drug companies. His arguments may seem very technical, but they are important, because this pseudoscience affects the lives of many thousands of people.

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    • Jay: I like that you include foreign policy in your discussion by mentioning
      Chomsky and Herman. Unfortunately, most Americans rely on mainstream
      media-news and entertainment-for their views of the world. In the third or fourth episode
      of season two of the Blacklist, the plot delves into the violence gene (warrior gene on the show) as well as mentioning secret government programs of thought control such as MK Ultra). This gave me the opportunity to explain a little about this to my wife, who is a health care professional. From what I remember, younger siblings of Juvenile
      delinquents were given spinal taps as a means of uncovering “the violence gene.”
      Activists pushed back against a violence gene conference in the DC area, and until the Blacklist episode I have heard nothing else about it. It is safe to say, however, that we still live in the shadow of the Eugenics Movement.

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  2. Thanks for the critic of the New York Times Magazine.

    Did you write the author Susan Dominus , with a short critic ?

    from the article [ the identical twins reared apart who each showed up for research wearing seven rings, or the reared-­apart sisters who rubbed their noses the same way and called it ‘‘squidging.’’]

    The wearing of rings is a cultural phenomenon.
    How many different ways are there to rub ones nose?

    Do they breath , eat, and use the bathroom the same way?

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  3. Once again, a really great article. I was wondering if you could offer additional insight.

    When looking at the data in numbers and the way twin studies have been put together, I too cannot help to see the major flaws, such as the EEA and the cohort effect and the bias in how volunteers come to the studies. From the data, along with the fact that little to no actual genetic proof has been found, I am lead to believe that if genes play a role in such things like personality, mental disorders, etc, then it is a relatively small amount, and environment has great power in modifying whatever genetic contribution there would be.

    However, then I read these amazingly coincidental stories of twins raised apart. Stories like the Jim Twins. And the giggle sisters. And the New Jersey fire fighters. Some of it I can easily dismiss as physical attributes. Some of it purely due to chance out of their control. Some of it merely due to the era in which they were raised and other cohort effects. But then there is the heap of stuff like responding exactly the same on tests. Writing the same exact odd ball sentence in different rooms when asked to write a random sentence, and making a nervous typo in the same spot. Calling scrunching your nose with your hand “squidging.” Being almost indistinguishable personality wise. Doing the same four jobs throughout life in the same order. All of these could be called coincidence, but these stories truly seem to be so outrageous as to defy environment, genetics, and cohort effects. And all of a sudden I am confounded again and fall into the pit of thinking we are all merely acting out genetic legacies.

    I know you are familiar not only with these studies, but of others as well, and I have read all of your articles where you attempt to debunk them. And like I said, I think you do to a certain extent.

    Obviously, if the Minnesota studies came up with hertibility estimates of roughly .50, I am guessing that either the twins mentioned above had a vast number of unreported dissimilarities, or that the few pairs mentioned were rare exceptions, despite the fact that Nancy Segal says they happen with reared apart twins more often then not. Do you know for a fact if non-similar twin data was dropped or not included? Or do you have any insight regarding how similar twin brain wiring seems to be when it comes to the thought process? (Writing the same sentence?).

    In summary, I really want to believe that I am not merely a product of my biological heritage, and that i have some degree of “free will” and that the many unique parts of who I am (my humor, quirky habits, original thoughts) do not simply lie in some gene expression, and that if I had a twin, I’d be looking in an identical mirror of the soul. That’s why I think your work is so important, since media and researchers can be quoted saying outrageous lies not grounded on anything resembling good science. (Showing how all data was extrapolated, interpreted, and fully open to peer review with solid proof of the mechanism that shows how the phenomena happens). Thoughts? Ideas? Other conspiracies you have proof of?

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  4. Dear Jinxer,

    These are very good questions. In my most recent book, “The Trouble with Twin Studies,” as well as my 2004 book “The Gene Illusion,” I explained why these stories about supposedly reared-apart twin pairs do not prove or even suggest anything about genetic influences on behavior. I am hoping to post something in my MIA blog on this topic by mid-January. Please look for it. Some of the points I raised in my earlier MIA blog on reared-apart twin studies relate to individual pairs as well.

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  5. Thanks Jay! I love your past articles on reared apart twins, and gene illusions, and look forward to additional information that you may have not addressed in past articles. I think the anecdotes, rather than the data, is the biggest obstacle to those arguing against the genetic paradigm, and the more we can look at those extreme stories and report on the differences that are there but don’t get reported, we can chip away at the biased explanations we have been given. People are swayed by hearing of twins raised apart both flushing before they go, wearing rubber bands on their wrists, etc. I have heard Segal’s take on this extensively, and though I see glaring holes in her thinking (her study of non related look a likes, for instance, proves nothing because the lookalikes are not together and interacting with the same individuals together) she is quite convincing on her tangents of all these unique quirks and testing done.

    Thank you for being a balance in a much biased debate

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