The taint of the Minnesota twin studies lingers on

Except when it doesn’t bother with the DZ part.

For me, it all began with the Mike Douglas show in the 1970s. If you’re not old enough to remember, that was an afternoon talk show, pre-Oprah, pre-Ellen, etc., sort of a primordial congenial-host-with-a-panel-of-guests kind of thing, and my mother often watched it, just as I was coming home from school. That’s where I learned about the Minnesota twin studies, as a nerdy teen in middle school/high school. I found that kind of stuff fascinating, anything about science would draw me to the TV. Or science-fiction/horror movies, although my mother tended not to have those on.

Douglas is the one on the left.

So I’m watching this, expecting to learn a little biology, but the Minnesota people (it might even have been Bouchard, I don’t recall) were doing a dog-and-pony show, very light on the science and rich in pandering to people’s biases about human nature, and my developing skeptical antennae were twitching. I remember them talking about how one pair of twins separated at birth had both grown up to be firemen. My future job was written in my genes, really? Another pair were married to women with the same first name. Now just hold on there, you’re telling me that somewhere in my genome was a hard-coded response to potential mates based on the sound of their name? Worse, another pair had given their dogs the same name (not the same name as their wives, the two dogs had the same name). There was no evidence that maybe there was a single locus for wife’s name/dog’s name.

I was taken aback. This sounded like complete bullshit. Are you telling me I can’t trust Mike Douglas?

I started researching the topic, back in the days when there was no google, and you had to physically go down to the library and read books to figure out what was going on. I quickly found lots of material, besides the sheer unbelievability of the nonsense they were spewing on daytime TV, that questioned the whole idea. It wasn’t hard. Now that I do have Google, here’s an an article that points out the methodological problems of twin studies.

  • Twins aren’t actually separated at birth. In these studies, 33% were separated after a year or more spent growing up together;
  • 75% of the pairs of twins still had contact with each other while growing up;
  • More than half (56%) were raised by a close family member;
  • In 23% of cases, the twins ended up being raised together again at some point or lived next door to each other.

Besides the fact that they were obviously cherry-picking coincidences for talk-show audiences, their premises were deeply flawed. These were bad studies with exaggerated conclusions drawn from flimsy data.

That link will also take you to this paper, A Reevaluation of the 1990 “Minnesota Study of Twins Reared Apart” IQ Study. It’s a damning analysis of one crucial result from the twin studies.

In 1990, Thomas J. Bouchard Jr. and colleagues published the widely cited 1990 “Minnesota Study of Twins Reared Apart” (MISTRA) Science IQ study. To arrive at the conclusion that “IQ is strongly affected by genetic factors,” Bouchard and colleagues omitted their control group reared-apart dizygotic twin (DZA) IQ score correlations. Near-full-sample correlations published after the study’s 2000 end point show that the reared-apart monozygotic twin (MZA) and DZA group IQ correlations did not differ at a statistically significant level, suggesting that the study failed the first step in determining that IQ scores are influenced by heredity. After bypassing the model-fitting technique they used in most non-IQ MISTRA studies, the researchers assumed that the MZA group IQ score correlation alone “directly estimates heritability.” This method was based on unsupported assumptions by the researchers, and they largely overlooked the confounding influence of cohort effects. Bouchard and colleagues then decided to count most environmental influences they did recognize as genetic influences. I conclude that the MISTRA IQ study failed to discover genetic influences on IQ scores and cognitive ability across the studied population, and that the study should be evaluated in the context of psychology’s replication problem.

Whoa. So the control group for their study of IQ in separated monozygotic twins, who are mostly genetically identical, was supposed to be measurements of IQ in dizygotic twins, who share on average 50% of their genes. That’s basically an essential comparison, as far as I’m concerned.

The Bouchard paper didn’t bother to do that comparison!

My mind is blown. They had the data, they must have done the statistical analysis, but they didn’t publish it in this well-known paper. They instead just compared identical twins to each other without bothering to look at how similar or different ordinary brothers and sisters were to each other, and declared that the numbers they got were sufficient to declare IQ to be significantly heritable!

The paper above dived in and re-did the analysis with the MZ twins and the DZ twins, and found that IQ was no less heritable in DZ twins than MZ twins. This does not fit what was expected if IQ was determined by genetics alone. Environment must play a significant role.

Never fear, hereditarians! Bouchard et al. had a prepared excuse to cover that eventuality. You see, environment is genetic!

We have seen that after bypassing their model-fitting procedures and their DZA control group data, Bouchard and colleagues based their conclusions about IQ heritability on the claim that the MZA correlation alone “directly estimates heritability.” However, they reached their conclusions only because they decided to count most environmental influences as genetic influences.

Bouchard and colleagues wrote in their 1990 Science article that one of the three “implications” of their genetic “findings,” and of behavioral genetic findings in general, was that MZA behavioral resemblance caused by the impact of environmental influences “is counted as a genetic influence,” because MZA pairs’ “identical genomes” cause them to create more similar environments for themselves (pp. 227–228). They continued,

MZA twins are so similar in psychological traits because their identical genomes make it probable that their effective environments are similar.… It is a plausible conjecture that a key mechanism by which the genes affect the mind is indirect, and that genetic differences have an important role in determining the effective psychological environment of the developing child. (Bouchard et al., 1990a, pp. 227–228)

The above statement is not an “implication” of the researchers’ findings; rather, it is an assumption upon which they based their findings.

Wow. That is remarkable. So everything is genetic! Therefore they didn’t have to worry about other variables or the confounding effect of differences in environment (or in the case of their flawed, not-actually-raised-apart twin studies, similarities in the environment) because, no matter what result they got, it was genetically determined.

I said at the outset that I was having problems accepting these twin studies when I was 15 years old. I was not a super genius 15 year old. As a teenager, I hadn’t even taken any classes in basic genetics, and even if I had, my experience of middle school science teaching tells me it would have been mediocre. I don’t think the published work of intelligent, established scientists should be rejected because it makes a teenager queasy.

But, man, the stuff they were trotting out on the talk show circuit was embarrassing. Somebody among them must have had similar reservations, and you’d think they would have tried to inject some meat into those public events. Why didn’t they? What was going on at the University of Minnesota?

It seems that Bouchard had some deeply seated bigotries, and he got the answers he wanted.

In a pre-MISTRA 1976 chapter entitled “Genetic Factors in Intelligence,” Bouchard argued in IQ-hereditarian fashion that “human intelligence,” as supposedly measured by IQ tests, “is largely under genetic control,” that social “class differences in intelligence have an appreciable genetic component,” and that due to reproduction patterns, the possibility of a decline in national intelligence “should be subject to continual scrutiny” (Bouchard, 1976, p. 193). Two decades later, Bouchard (1995, p. 417) and Lykken (1995, pp. 216–217) endorsed Richard Herrnstein and Charles Murray’s conclusion in The Bell Curve that “both genes and the environment have something to do with racial differences” in IQ scores (Herrnstein & Murray, 1994, p. 311).

Holy crap! I don’t think Bouchard said those things to Mike Douglas.

It’s clear that we’re still seeing the legacy of Francis Galton and eugenics, that too many scientists have a bias favoring genetic determinism. We’ve been struggling to eradicate the weedy toxins of eugenics, but we have to dig deeper and clear out the ongoing poison of these badly done twin studies. We’re probably going to have to bear that burden for at least another century.

Then we have to start on all the badly done GWAS studies…

Are you arguing that genetics supports your racism?

The American Society for Human Genetics begs to differ.

As the American Society of Human Genetics (ASHG) joins others in deepest sorrow and outrage over the unfathomable recent tragedies in Uvalde, Texas and Buffalo, New York, the human genetics community is appalled at the news that the shooter in the hate-fueled mass killing in Buffalo rooted his racist beliefs by misusing and misrepresenting the science we strive to advance each day. As we have in 2018 and again in 2020, the human genetics community rejects in the strongest possible terms any attempt to twist and warp genetics knowledge to advance bogus racist ideology or try to legitimize through science the fundamental hatred that forms white supremacy’s evil core.

The fundamental fact from human genetics is this: the human genome tells the profoundly powerful story of a single humanity – one species able to thrive by adapting in subtle but important ways to our environmental and evolutionary forces over thousands of years in every corner of the planet. That variation is an enormous and profound strength and is central to efforts to understand and apply this knowledge to serve humanity.

As scientists and citizens in this one humanity, it is our duty to condemn falsehoods that enflame violence and to champion scientific knowledge and fact. ASHG’s hearts, minds and long-term goals remain fully committed to advancing equity, diversity and inclusion in science, health and society.

Genetics is far messier than most people know, so a good rule of thumb is to question simple answers.

Ancient Romans were diverse? Who would have thought it?

I wouldn’t have guessed that they’d ever get DNA from the dead of Pompeii, but they have. It’s not complete — heat isn’t compatible with DNA preservation — but they were able to make some mundane conclusions.

The man’s genome assembly had just 0.42x coverage, indicating that the reads had little overlap, and there were gaps. Still, according to Scorrano, the sequence was good enough to analyze certain aspects of the DNA. The results suggested the Pompeian man was genetically similar to modern Mediterranean populations and, when compared to other published genomes from ancient Rome, that he was closely related “to Imperial Roman Age individuals,” Scorrano says, adding that that’s what the team expected to find. But at the same time, he notes that Rome was packed with people from diverse genetic backgrounds back then. In fact, the markers of the man’s maternal and paternal lineages were absent among those previously published sequences, which suggests the region had high genetic diversity during that time.

The Italian Peninsula was “incredibly heterogeneous” when Vesuvius erupted—people were “coming from all over the empire” into Rome or into port cities like Pompeii, says University of Chicago archaeologist Hannah Moots, who did not participate in the study but has previously characterized the genomic pool of ancient Rome. It is exciting to have genomes from Italian regions outside Rome, she says, adding that looking at sites like Pompeii is “really interesting” because they can provide insights into more rural areas.

Mundane isn’t bad — it’s what was expected. And they did find some novel markers. Just learning that Roman society was diverse is a good reminder to all those people who think monocultures are superior.

What are the responsibilities of geneticists?

Still works. Just replace “philosophy” with “genetics”

Janet Stemwedel has published an essay in Scientific American. It’s good. You should go read it. It’s also on a subject that I, someone who teaches genetics to college students, worry about. All you have to do is look at racists on the internet, or any of those gomers of the “Intellectual Dark Web”, and you’ll find them chattering away about their version of genetics, citing genetics papers they’ve read or glanced at, but barely understand, and drawing sweeping, and unlikely, conclusions from, for instance, GWAS studies. We’re all so interested in what we can do that we aren’t cautious enough about saying what we can’t do, and what are the invalid interpretations that can trap people searching for genetic certainty in their genomes.

She has some strong suggestions.

For one thing, they [scientists] must be frank and vocal about the weakness of studies that purport to find correlations between race and differences in traits like intelligence or propensity violence. This includes methodological weaknesses like treating IQ as a good proxy for intelligence, or treating “race” as something with clear genetic grounding. A finding that particular genes or sets of genes are associated with a complex behavior does not demonstrate a causal relation or rule out the importance of environmental factors—and indeed, the assumption that genes and environment vary independently is usually false. An average difference in a trait associated with a set of genes between two populations does not rule out that the individual variations within those populations may be greater than the average difference between populations. All of which is to say it’s hard to draw conclusions that are strong, clear and well-supported from much of this work. To the extent that race science is just bad science, scientists have a duty to call it out, rather than letting it stand unchallenged.

I’ve been thinking that I ought to incorporate one of Richard Lewontin’s books into my genetics class — something like It Ain’t Necessarily So : The Dream of the Human Genome and Other Illusions, maybe. The catch is that in a traditional genetics course, we have an obligation to teach the core concepts, and taking time to teach about how genetics is misused is sometimes premature.

For another thing, scientists must do some soul-searching about why they are so motivated to look for evidence that traits like intelligence or propensity to violence are written in our genes, or that they would be different for people in different racial groups. Of all the bits of truth they could discover about our complex world, why this focus? Could it be that scientists are following their preexisting hunches, biases that come from being humans living in a culture built around those biases—or that funders are seeking scientific validation for their biases? Any scientist who dismisses this possibility has forgotten that objectivity requires the communal project of scrutinizing scientific conclusions to find how they might be mistaken.

I’ve got a few awful books on my bookshelf, often written by evolutionary psychologists, that make me wonder about the mental state of the authors. They have some grand theory about human behavior that I know can’t possibly be backed up by significant genetics research, but apparently the public wants that nice pat answer to explain why everything is the way it is.

Also, a lot of those kinds of books seem to be written by professors of marketing. Seriously, if you see a book that purports to be about biology, and the author is employed in a business school, don’t waste your time. Which leads into Stemwedel’s next point…

There’s a further question scientists ought to ask themselves when reflecting on why they study the scientific questions they do: What will the knowledge I’m building be good for? How could it be put to use? Do scientists imagine that a finding of genetic differences in intelligence among racial groups would be used to drive more school funding to Black and brown communities, or as a justification to focus school funding on white communities? Or that a finding of genetic differences in propensity for violence among racial groups would be used to do anything but double down on current overpolicing of communities of color?

In the case of James Watson, for example, I think he’s made a career of trying to buttress evidence that he is an intrinsically superior person. They didn’t call him Lucky Jim for nothing — he stumbled into a major discovery, and I wonder if he wonders what might have made him so fortunate. It can’t possibly be that anyone with the right training could have done it, so he finds a refuge in the fact that he’s Scots-Irish. Others know that the status quo has treated them well, so they want to perpetuate what is currently a racist society for the benefit of themselves and their children. Others, I think, are so steeped in a culture of racial bias that they don’t even think about it — black people must be inferior, so let’s search for a rationalization for holding what is an odious belief.

It’s probably a messy mix of all of those things, and more. I’m pretty sure that if genetics has broad fuzzy edges that psychology is probably even worse.