The New York Times Magazine has a long, interesting nature vs. nurture article about two pairs of identical twins who were switched soon after birth in the hospital in Colombia. Two of the boys were raised as fraternal twins in the big city of Bogota, while the other two were raised as fraternal twins in an isolated farming village a five-hour walk from the nearest road. The country boys eventually moved to Bogota and got jobs as butchers, where the city boys had white collar jobs. Eventually, mutual acquaintances and Facebook helped bring them together.

The only problem with the article is that it lacks a simple grid to help you keep straight in your head the four names, so I constructed the one above for your convenience when reading.

Here’s a short verbal cheat sheet as well, numbering them 1 to 4 from left to right in the top row, then left to right in the bottom row:

1. Jorge: conceived in city, raised in city, engineer, identical twin of William, adoptive brother of Carlos

2. Carlos: conceived in country, raised in city, accountant, identical twin of Wilber, adoptive brother of Jorge

3. William: conceived in city, raised in country, butcher shop manager, identical twin of Jorge, adoptive brother of Wilber

4. Wilber: conceived in country, raised in country, butcher, identical twin of Carlos, adoptive brother of William

The city-conceived identical twins Jorge and William look a little like a more mestizo version of the Mexican movie star Gael Garcia Bernal. The country-conceived Carlos and Wilber look a little like the late Venezuelan president Hugo Chavez, a triracial pardo.

The country-raised boys were raised in a two-parent peasant family and didn’t get much education, while the city-raised boys were raised by a single mother housekeeper, but went to pretty good public schools.

Nancy Segal, a professor at Cal State Fullerton who worked on the famous Minnesota Twins study under Tom Bouchard and has since become the Queen of Twins, makes a central appearance in the article.

The Mixed-Up Brothers of Bogotá After a hospital error, two pairs of Colombian identical twins were raised as two pairs of fraternal twins. This is the story of how they found one another — and of what happened next. By SUSAN DOMINUS JULY 9, 2015

I’ll excise most of the personal stuff, which is pretty interesting although hard to follow without my photo grid above.

… By studying the overlap of traits in fraternal twins (who share, on average, 50 percent of their genes) and the overlap of those traits in identical twins (who share 100 percent of their genes), scientists have, for more than a century, been trying to tease out how much variation within a population can be attributed to heredity and how much to environment. ‘‘Twins have a special claim upon our attention,’’ wrote Sir Francis Galton, a British scientist who in the late 19th century was the first to compare twins who looked very much alike with those who did not (although science had not yet distinguished between identical and fraternal pairs). ‘‘It is, that their history affords means of distinguishing between the effects of tendencies received at birth, and those that were imposed by the special circumstances of their after lives.’’ Galton, who was Darwin’s cousin, is at least as well known for coining the term ‘‘eugenics’’ as he is for his innovative analysis of twins (having concluded, partly from his research, that healthy, intelligent people should be given incentives to breed more). His scientific successor, Hermann Werner Siemens, a German dermatologist, in the early 1920s conducted the first studies of twins that bear remarkable similarity to those still conducted today. But he also drew conclusions that for decades contaminated the strain of research he pioneered; he supported Hitler’s arguments in favor of ‘‘racial hygiene.’’ In seeking genetic origins for various traits they considered desirable or undesirable, these researchers seemed to be treading dangerously close to the pursuit of a master race. Despite periods of controversy, twins studies proliferated. Over the last 50 years, some 17,000 traits have been studied, according to a meta-­analysis led by Tinca Polderman, a Dutch researcher, and Beben Benyamin, an Australian, and published this year in the journal Nature Genetics. Researchers have claimed to divine a genetic influence in such varied traits as gun ownership, voting preferences, homosexuality, job satisfaction, coffee consumption, rule enforcement and insomnia. Virtually wherever researchers have looked, they have found that identical twins’ test results are more similar than those of fraternal twins. The studies point to the influence of genes on almost every aspect of our being (a conclusion so sweeping that it indicates, to some scientists, only that the methodology must be fatally flawed). ‘‘Everything is heritable,’’ says Eric Turkheimer, a behavioral geneticist at the University of Virginia. ‘‘The more genetically related a pair of people are, the more similar they are on any other outcome of interest’’ — whether it be personality, TV watching or political leaning. ‘‘But this can be true without there being some kind of specific mechanism that is driving it, some version of a Huntington’s-­disease gene. It is based on the complex combined effects of an unaccountable number of genes.’’ Arguably the most intriguing branch of twins research involves a small and unusual class of research subjects: identical twins who were reared apart. Thomas Bouchard Jr., a psychologist at the University of Minnesota, began studying them in 1979, when he first learned of Jim and Jim, two Ohio men reunited that year at age 39. They not only looked remarkably similar, but had also vacationed on the same Florida beach, married women with the same first name, divorced those women and married second wives who also shared the same name, smoked the same brand of cigarette and built miniature furniture for fun. Similar in personality as well as in vocal intonation, they seemed to have been wholly formed from conception, impervious to the effects of parenting, siblings or geography. Bouchard went on to research more than 80 identical-­twin pairs reared apart, comparing them with identical twins reared together, fraternal twins reared together and fraternal twins reared apart. He found that in almost every instance, the identical twins, whether reared together or reared apart, were more similar to each other than their fraternal counterparts were for traits like personality and, more controversial, intelligence. One unexpected finding in his research suggested that the effect of a pair’s shared environment — say, their parents — had little bearing on personality. Genes and unique experiences — a semester abroad, an important friend — were more influential. As pure science, the study of twins reared apart has troubled some researchers. Those twins either self-­select and step forward or become known to researchers through media reports — which are less inclined to cover identical twins who do not look remarkably alike, who did not marry and divorce women of the same name or choose the same obscure hobby. Identical twins who do not look remarkably alike, of course, are also less likely to be spotted and reunited in the first place. And few studies of twins, whether reared apart or reared together, have included twins from extremely different backgrounds.

Twins reared apart studies are also adoption studies. Adoption agencies try to restrict the range of adoptive parents. One French adoption study (not involving twins) tried to find examples of 20 trans-class adoptions but could only find 18. Their data, limited as it was, suggested that IQ at 14 was 59% nature, 41% nurture.

‘‘Every study will have its critics,’’ says Nancy Segal, a professor at California State University, Fullerton, who worked with Bouchard from 1982 to 1991. ‘‘But studying twins reared apart separates genetic and environmental effects on behavior better than any research design I know.’’ The twins knew the research would require them to submit, over the course of a week in March, to several probing interviews, individually and in pairs, as well as hours holed up in a conference room filling out questionnaires. There would be questions about their homes, lives and education, as well as personality and intelligence tests. Segal told them that she was interested in writing a book about them (Montoya would later collaborate with her), and the young men were enthusiastic subjects. … The Myth of Identical Twins … By the time that embryo is five or six days old, which is when a majority of fateful twin splits occur, some of those cells, by chance, go to one twin and some to the other. This means that the expression of some genes in one of those future twins is already, in subtle ways, likely to be different from the expression of genes in the other future twin, theorizes Harvey Kliman, the director of the reproductive and placental research unit at the Yale School of Medicine. From the moment that most identical twins separate, they may well have different epigenetics, a term that refers to the way genes are read and expressed, depending on environment. They are already different products of their environment, the environment being whatever uterine conditions rendered them separate beings in the first place. The casual observer is fascinated by how similar identical twins are, but some geneticists are more interested in identifying all the reasons they might differ, sometimes in significant ways. Why might one identical twin be gay or transgender and not the other? Why do identical twins, born with the same DNA, sometimes die of different diseases at different times in their lives? Their environments must be different, but which aspect of their environment is the one that took their biology in a different direction? Smoking, stress, obesity — those are some of the factors that researchers have been able to link to specific changes in the expression of specific genes. They expect, in time, to find hundreds, possibly thousands, of others. The meta-­analysis published this spring in Nature Genetics, which examined 50 years of studies of twins, arrived at a conclusion about the impact of heredity and environment on human beings’ lives. On average, the researchers found, any particular trait or disease in an individual is about 50 percent influenced by environment and 50 percent influenced by genes. But that simple ratio does not capture our complicated systems of genetic circuitry, the way our genes steadily interact with the environment, switching on, switching off, depending on the stimulus, sometimes with lasting results that will continue on in our genome, passed to the next generation. How an individual’s genes respond to that environment — how they are expressed — creates what scientists call an epigenetic profile.

Epigenetics is a real scientific field, but it’s often puffed up for ideological reasons that turn out to be confused upon close analysis. As I blogged in 2012 about epigenetics:

I have to say that I’ve never quite gotten the excitement over epigenetics as a revolutionizing nature-nurture debates. This is not to say that the study of epigenetics isn’t valuable in and of itself, it just seems to have less implication for the kind of arguments that people really care about than its publicists assume. If I say, “Twin studies, adoption studies, and so forth suggest that for a lot of traits, there’s roughly a 50-50 breakdown between the effects of heredity and environment,” over the last few years, I constantly get told that: “Oh, no, that’s so 20th Century. You see, some of the genes are also being affected by the environment.” Me: “Okay, but that still leaves us with the results of twin and adoption studies. So, what it sounds like you are saying is that genes aren’t just 50% of the importance, they’re something like 75%, but maybe 1/3rd of the genes are influenced by the environment, so we’re right back to 50-50, right? I mean, we have to get back to what the studies report.”

This is not to say that epigenetics might not someday have medical applications, but the quick leap to assuming that the existence of the field of epigenetics validates the whole Kristoff worldview of poor black children not hearing enough talking etc etc is a heroic leap. Dominus’s article continues:

Bouchard was influential in convincing his fellow researchers, as well as the public, that some significant part of who we are is influenced by DNA, which was hardly a given when he started his work. Spector and Craig, by contrast, are trying to identify how, exactly, we change in response to the environment. Their essential question is different: How can science identify genes that have been flicked on or off, with potentially harmful results, so they can be switched back the other way? Traditional twin studies were perceived to be seeking the immutable; epigenetic twin studies try to clarify what, in us, is subject to change — and more specifically, what mechanisms make that change happen. The process of spending time with Segal and Montoya and sharing their life histories necessarily changed the young men’s experience of their reunion. Carlos seemed surprised at one point when Segal asked him to describe the ways in which he and Wilber differed. ‘‘Well, the thing is, we’ve always focused on what our similarities are,’’ Carlos said. ‘‘We haven’t actually talked about our differences.’’ He seemed pleased, at last, to be given the opportunity. At the time, Carlos pointed out that he liked older women, while Wilber liked younger ones. But the answer was, of course, far more complicated. Carlos [country-conceived, city-raised] was like Wilber [country-conceived, country-raised] in large, sweeping ways, and unlike him in infinite small ways: the expressions that darted across his and his face alone, the thoughts and worries that filled his mind. Carlos was, for better or for worse, more cynical than Wilber, more suave; Wilber was more joyful around small children, quicker to laugh out loud. Jorge and William, too, have obvious differences. Jorge [city-conceived, city-raised] is a dreamer, a restless traveler, an optimist who believes that ‘‘if you give your best to the world, it will give its best back.’’ William’s [city-conceived, country-raised] face, more narrow, more gaunt, reflects a far warier outlook. ‘‘Nothing in life is easy,’’ he remarked once, a sentiment that you could hardly imagine Jorge expressing.

The boys raised as rural peasants tend to have peasant outlooks (see Jean de Florette for more on the subject).

Before starting her research, Segal would not have been surprised if each young man tested similarly to his identical twin, despite their different environments. But her preliminary results, she said, show that on a number of traits, the identical twins were less alike than she initially anticipated. ‘‘I came away with a real respect for the effect of an extremely different environment,’’ Segal said. Perhaps the results merely indicate that people raised in deeply rural environments, with little education, take tests in a wholly different manner from those who attended a university. William (city-conceived, country-raised), who managed a small business with competence, at times seemed overwhelmed by the test. But Segal considered the young men’s story a case history that might provoke further research, inspiring others to seek out more examples of twins reared apart with significantly different upbringings, whatever they were.

Since the 1990s, I’ve always assumed that you’ll go least wrong assuming a 50-50 split until proven otherwise.

This story of two pairs of identical twins interchanged at birth was anticipated in the 1988 comedy Big Business with Bette Midler and Lily Tomlin each playing city and country versions of switched identical twins:

And here’s the movie’s switching-at-birth scene:

https://www.youtube.com/watch?v=e73Jt0W8vjA