What Twins Separated At Birth Teach Us About Human Genetics - Nancy Segal

Nancy Segal is a professor at California State University, an author and one of the most prominent twin-study researchers on the planet. What makes you the person you are? Is it your genetics or your environment? When twins are either accidentally or purposefully separated at birth, it presents a fascinating view into this debate, shedding light on the influence of both traits and environments on the outcomes we get in life. Expect to learn the craziest similarities between twins who have been raised apart, how it's possible to have a pair of twins born at the same time to two different fathers, what happens when twins meet for the first time, what you can learn from triplets that you can’t learn from twins, just how big of an impact genes and environment are on the traits we see in people, how important of a role chance plays in our lives and much more... Sponsors: Get the Whoop 4.0 for free and get your first month for free at http://join.whoop.com/modernwisdom (discount automatically applied) Get a Free Sample Pack of all LMNT Flavours with your first box at https://www.drinklmnt.com/modernwisdom (automatically applied at checkout) Get 5 Free Travel Packs, Free Liquid Vitamin D and more from AG1 at https://drinkag1.com/modernwisdom (discount automatically applied) Extra Stuff: Get my free Reading List of 100 books to read before you die → https://chriswillx.com/books/ To support me on Patreon (thank you): https://www.patreon.com/modernwisdom #twins #genetics #behaviour - 00:00 How Evolutionary Psychology Explains Twins 04:51 Unique Connections Between Identical Twins 08:22 The Rare Occurrence of ‘Half Twins’ 16:22 How Do Twins Know They’re Twins? 21:02 When Separated Twins Are Both Gay 25:00 Craziest Similarities Between Separated Twins 35:19 Do Twins Also Share Illnesses? 43:25 The Ethics of Separating Twins at Birth 48:31 Why Do So Many People Have an Issue with Behavioural Genetics? 52:57 How Much Can Rearing Change a Child? 1:04:14 The Family Dynamic of Bi-Racial Twins 1:07:03 Common Criticisms of Twin Studies 1:11:34 ‘Tell Me Who I Am’ on Netflix 1:14:10 Where to Find Nancy - Get access to every episode 10 hours before YouTube by subscribing for free on Spotify - https://spoti.fi/2LSimPn or Apple Podcasts - https://apple.co/2MNqIgw Get my free Reading List of 100 life-changing books here - https://chriswillx.com/books/ - Get in touch in the comments below or head to... Instagram: https://www.instagram.com/chriswillx Twitter: https://www.twitter.com/chriswillx Email: https://chriswillx.com/contact/

Speaker names marked ? are inferred from speaking time and the show’s known hosts — they are not voice-verified.

• 0:00Chris Williamson?

  How do you describe what you work on when somebody asks?

• 0:04Speaker 01

  Well, I tell them that I'm a developmental psychologist, but my interests also cover behavioral genetics and evolutionary psychology. And I'm passionate about twins because twin studies are a simple and very elegant way of combining all three developmental psychology, behavioral genetics, evolutionary psychology, different levels of analysis and application. But also, I'm a twin myself. And so I really think that when you're personally invested in something, you have greater interest and passion for the topic. And so my whole career, I liken to a candy store. I've just had a wonderful ride and the ride is continuing.

• 0:46Chris Williamson?

  That's how I feel when I get to speak to anyone from the EP world, or the behavioral genetics world, or the sex research world. It's the absolute most fun. William Costello, the guy that's doing all of this stuff on incels at the moment, famously keeps on reminding me that research is me-search. It's a little bit different for him doing it on incels and you doing it on twins, given that you're a twin. I don't know what it says about William, given that that's what he's studying. What is the evolutionary psychology angle of twin research? I can see how behavioral genetics comes in. You know, we're splitting apart genetically and environmentally, what the contributing factors are. But I'm less sure about the others.

• 1:26Speaker 01

  Right. So, one of the very provocative theories that was launched was kinship genetic theory by William Hamilton, who asserted that we feel greater cooperation, altruism, investment in people with whom we share higher degrees of genetic relatedness. We don't consciously do the calculations in our head, but we behave as though we do. And so I've always known for years that identical twins are more cooperative.

• 1:55Speaker 01

  Closer socially than fraternal twins are on average. And so I felt that this was another level of analysis that I could bring to twin studies. Because many people say, well, they're they're closer because they look alike or people encourage it. But I I don't believe that's the case because behavior is not built on appearance. Behavior is built on the brain. And so I always felt that there was some deeper level to this. And so I've been able to use twins. I've been able to use unrelated look alikes. I've been able to use virtual twins, many, many types of relationships that vary in genetics and in environmental connectedness. And the findings are are beautiful because they really converge on the same thing.

• 2:40Speaker 01

  You know, I remember when I was doing my doctoral dissertation, my first major study, and I used seven to 11 year old children, twins. And what I did was I put them into a puzzle completion situation, a kind of semi-naturalistic study where they all completed the same puzzle under the exact same circumstances with the exact same instructions. And without a word from me, and I kept the mothers out of there, the identical twins just did this orchestrated dance, beautifully coordinated. There was little rough play. Everybody was very cooperative and they were very successful at puzzle completion. But the fraternal twins, on the other hand, tended to grab different pieces of the puzzle to their side of the table and work on it independently. And the whole thing looked like a mess.

• 3:25Speaker 01

  And there were lots of elbow jabs and snatching of pieces. And so that really told me that twins can tell us so much just by being themselves.

• 3:35Chris Williamson?

  What is your explanation for why identical twins and fraternal twins had that difference? For the people that don't understand, am I right in saying that fraternal twins are essentially just simultaneously born brothers and sisters?

• 3:49Speaker 01

  That's correct. Identical twins result when a single fertilized egg divides between the first and fourteenth day of conception, whereas fraternal twins result when a mother releases two eggs at the same time, separately fertilized by two sperm. And so the kids share fifty percent of their genes on average by descent, which is exactly the same as ordinary siblings. So I think that what is going on here, Chris, is that identical twins who have the same genes are responding to the world the same way. They have similar temperaments. They process information the same way. And so all of those ingredients allow them to work more cooperatively in a joint situation, whereas fraternal twins bring very different interests and understanding and abilities to a particular task.

• 4:31Speaker 01

  I can tell you that I have a fraternal twin sister and in a puzzle completion task as kids, we'd be at each other's throats. We had very different understandings and ways of doing things, and we still do. We're close sisters. I think a lot of siblings get closer as they age, but nevertheless, as children, we would have been definitely on the competitive side.

• 4:50Chris Williamson?

  I wonder whether teams, it would very much depend on what the activity is that you're doing, but I can imagine some activities in which you want someone that's very similar to you, but in other activities, you might actually want someone who has a different skill set. You want to be the analytical one, you want them to be the creative one, you want to be the slightly more risk averse one, you want them to be the slightly more adventurous one. So I imagine that depending on what the task is at hand, you could have scenarios in which being identical twins would be an advantage or sometimes a disadvantage.

• 5:20Speaker 01

  Yes, I think that's right. For example, if you're very skilled, say, at coming up with great ideas, but you don't know how to put them into play, you might want somebody who's more analytical, more statistical minded, to really complement you. And so to that degree, somebody a little different would be helpful. But identical twins would probably just pick a topic or pick an area where they both excelled and they do very well at it. One area I'm really fascinated in is twins and sports. And it is amazing to see these matched levels of elite athletes. You know, it's extraordinary one person wins an Olympic event, but even more extraordinary when the other one comes in second. How is this possible?

• 6:03Speaker 01

  Part of it is because of the way their bodies are built, their similar motivations, their similar interests. And the fact that in many cases, a single, a victory for one is a victory for both. And it's hard to get your head around that kind of selflessness. But I've heard it repeated so many times.

• 6:21Chris Williamson?

  What about that? What about the degree of emotional connection between identical twins? I mean, there's tales as old as time about they've got secret languages and they can mind read and do stuff like that. But have you found comparing it with normal siblings and fraternal twins? Is there an extra degree of connectivity, of emotional investment, of kinship? As would have been predicted by that theory?

• 6:51Speaker 01

  I think there's no question that there is an emotional connection that goes far beyond any kind of relationship. In fact, I would assert that the identical twin bond is closer than any other relationship.

• 7:01Chris Williamson?

  Even more than mothers with children?

• 7:03Speaker 01

  Yes, and I would, I say that because I have a study on the loss of a twin on bereavement. And I wanted to understand two things. Do identical twins grieve more than fraternal twins, mirroring what you see in their relationships? And is there something unique about twin loss? And of course, this was all framed by evolutionary theory, in particular, kinship genetics. And I did find that identical twins grieved more for their co-twin than they did for any of the loss of any other relative, whether it was a mother, a father, a non-twin sibling, a grandparent, an aunt or uncle. Of course, when you get to those, you know, second degree relatives, the genetic relatedness dips down.

• 7:42Chris Williamson?

  I'm guessing that's the same for a son or a daughter as well, then?

• 7:46Speaker 01

  Yes, yes, but well, let me backtrack on that. I have very few sons and daughters, very few twins lost children, for which I'm very grateful. But that would be theoretically, it would be a fascinating comparison, because with identical twins, you share all your genes with children only fifty percent. Whereas fraternal twins, you share half on average with your twin, and you share fifty percent, for sure, with your child. So I would expect much greater variability among the paternals.

• 8:15Chris Williamson?

  Very interesting.

• 8:17Speaker 01

  Very interesting, but I really hope I never get to do that comparison, because I don't want anyone to lose a child.

• 8:22Chris Williamson?

  I, one of the other very interesting things that I learned about when looking through your research, is that there are times when a mother will release two eggs, and will have multiple sexual partners within that pregnancy window, within that fertility window, and end up with, I don't even, what, what are the, the, like, half, half twins? Like, what, what are they called?

• 8:49Speaker 01

  Well, the medical term for that is superficundated twins, which means that because she had two eggs released, and she had two different partners, each partner got to one egg in that four-day fertilization window, and the children are really genetic half siblings. But I regard them as a legitimate pair of twins, because this can come out naturally, and it can also come about through artificial reproductive assistance. You know, as you know, and I've told you, I have a book that's coming out August eighth, called Gay Fathers' Twin Sons: The Citizenship Case That Captured the World. And this is a case where two gay fathers, who were very much in love with each other and married, decided to raise a

• 9:31Speaker 01

  family. And so they contacted a donor and a surrogate, and they each provided sperm to fertilize these eggs. And it turned out that the top two embryos were each, each created by one father. And those are the ones they implanted. So they replay a naturally occurring situation. It's very fascinating.

• 9:53Chris Williamson?

  Tell us that story.

• 9:55Speaker 01

  Well, what happened was there was a young man named Andrew from the United States who decided to get a master's degree at Tel Aviv University. And then he met another young man, Elad, and they fell in love and married in Canada in 2010.

• 10:08Chris Williamson?

  Tel Aviv, Tel Aviv isn't fantastic for trying to get your gay wedding across the line.

• 10:12Speaker 01

  Not really, no. In fact, Israel now will recognize gay marriage, but they won't allow it in their country. If you marry elsewhere, it's recognized. At any rate, they moved to Canada because marriage, gay marriage was allowed there in 2010, and Andrew also had dual citizenship. In 2016, they decided to have a family, and that's when they gave birth these beautiful boys, Aiden and Ethan. And the problem became when the boys were four months old, and they decided to move to Los Angeles. And when they tried to get the boys the passports at the consulate in Toronto, they were just hit with a number of very rude and intimate questions, such as, where do these children come from? Who's the father of this one? Who's the father of that one?

• 10:57Speaker 01

  Intimate details that they had no plans to reveal, not even to their parents. The only ones who knew were DNA lab and the surrogate. Beyond that, nobody knew the relationship of the kids. So now their genetic linings are all hanging out on the clothesline. Everybody knows. And so the upshot was that they issued a passport to the little boy who had, who's created with the sperm from the American father, and a tourist visa to the other one. And so this threatened to tear their family apart. Tourist visas are good for about six months. They are renewable, but it was a terrible situation. So when they did come to the US, it was about 2017, 2018. And that was when, when former President Trump issued these bans on Muslim immigration.

• 11:42Speaker 01

  So all the immigration attorneys were at the airports, taking care of these cases. But... They did find a wonderful group in New York called Immigration Equality. Lawyers that are very concerned with gay couples, HIV-infected individuals, other minorities, and they work pro bono on behalf of these couples. And Andrew and Lot's case came about at the perfect moment because they already had three other couples, transnational, who had children outside the US. But, Chris, twins capture attention, and this case really got into the media because the idea of separating two little boys who were born four months apart is unconscionable. And that was a real threat to the family.

• 12:26Speaker 01

  So the case was the family's name, DeBash Banks, versus the US State Department and Rex Tillerson, who was then Secretary of State, later Mike Pompeo. It was a very high-profile case that almost reached the Supreme Court. It took four years to resolve. There were moments when the government appealed. You have an appeal window of 60 days, and they would appeal on the 59th day after the circuit court ruled in favor of the family. Eventually, the case settled, no more appeals. And now they're living out here in California. I can't tell you what a lovely family they are. And all you see when you look at them are two really devoted parents and two very happy children. That's it. You don't see anything else.

• 13:09Chris Williamson?

  Wow. What a story. How much of this do you think is concealed homophobia from organizations that maybe and then I guess actually a combination of concealed homophobia and concealed Islamophobia intersectionally combining to create this?

• 13:30Speaker 01

  I think that is certainly one of the factors. And I think whether you're homophobic or not, if you just simply disagree with the idea of it, then I think that that can play a role.

• 13:42Chris Williamson?

  Sorry, maybe homophobia might be the wrong term there that just.

• 13:47Chris Williamson?

  There's less preference given. It's not like you need to discriminate against, but it's a slippery slope from, well, is the treatment the same? I'm going to guess that it would be treating somebody different on the basis of their sexual orientation. Probably that's like a rough definition of homophobia. So it probably is. It probably meets the criteria. Not quite the same as going out of your way to call somebody a slur. But if you're not treating them the same way that you would do as a heterosexual couple or a couple that are both from a European country or whatever. Yeah, maybe it does meet the criteria.

• 14:20Speaker 01

  Yeah. So at any rate, I think that's really plays into it. And then there's another element that I noticed that one of the lawyers brought to my attention. And that is that the government just seems in some ways to make things difficult. I don't know why, but they just seem to make things difficult for these families who just simply want to lead their lives. And so many politicians say families first, and yet what about this family? And the wonderful thing about this case was it did settle in favor of the family and it has been helpful to future families. The Foreign Affairs Manual, which is what is relied upon in the consulates, was modified because of this. And it's still the case that officers have some measure of discretion in interpreting some of these guidelines and rules.

• 15:04Speaker 01

  But nevertheless, it's gone far. And these two fathers could have taken an easy way out. They could have gotten a green card for the child. They wouldn't have had any publicity. But they were both very eager to make a statement and to leave some kind of lasting change in society. They both had difficult times growing up as gay men, as gay teenagers. They both, and so they know what it was like to suffer and to stay strong and to make a difference. And so that was an attitude they carried with them into this issue as well. And I think they're terrific. I mean, they're just terrific. Right now, they're over in Europe having a vacation. They're doing what all families do. And in fact, one of them said to me,

• 15:47Speaker 01

  We're boring. All we do is we take our kids to Disneyland, we watch Netflix, we go to the market. And we're just boring people. It's just that we happen to be two gay guys. And they're right. They are boring. But I love them.

• 16:02Chris Williamson?

  I am very, very glad that you've managed to find such an interesting story. And was it three identical strangers? You know, that managed to do something very similar with regards to just captivating people's attention. You said it earlier on, there's something about twins, especially identical twins and triplets, that are just so captivating. One of the things that you brought up earlier on that's still playing on my mind was you mentioned the kinship genetics prediction, that the closer you are genetically related to somebody, the more you should care, the more that you would be invested. How is it that twins know that they're twins in this case?

• 16:43Speaker 01

  Well, that's a very good question. And I think they know when they can see the other one looking like them, or even if they're fraternal twins, you know, there's someone they've grown up with, they've been in the house. Now, in evolutionary psychology, there are two cues that have been talked about in terms of sibling relatedness or knowledge of a sibling.

• 17:05Chris Williamson?

  Is one of these the Westermark effect? Because this is my favorite.

• 17:09Speaker 01

  I wasn't going to go there, but we can go there later because I think that's really fascinating. I have talked about that. And I'm going to tell you some stuff that's going to startle you. But all right, let me just go with this for a moment. So the two cues that have been talked about in terms of sibling knowledge, knowledge of a sibling, is maternal association. So if you see another baby with your mom, you figure that's a relationship to you. And the amount of co-residence. So if you live with a child, another kid, that means that that's probably yours. That's interesting, but it's not enough because most identical and paternal twins live at home with same mom, same dad, same house. And yet we still have these differences in social relatedness between the identicals and the paternals. Nobody teaches them that.

• 17:54Speaker 01

  So I think that it's recognizing similarities and it goes beyond just the physical feature. Because as I told you earlier, I do studies of unrelated lookalikes who look as alike as identical twins, and they are nowhere as alike in personality and very few of them develop close relationships that are lasting.

• 18:14Chris Williamson?

  Just to interject there, what that would prove is that the reason that identical twins are the same is not because people treat them the same.

• 18:22Speaker 01

  Yes, but, right, because they evoke similar treatment from others. So, see, I'm sort of turning the process around. I do think people treat identical twins more alike, but it's because they evoke similar reactions from people. And we call that evocative gene environment correlation in behavioral genetics. That's what it's called. So, at any rate, I think that with identical twins, whether raised apart or raised together, they perceive certain similarities of themselves that draw them together. Beyond their appearance, it's their mannerisms, their interests, their temperaments, all those kinds of things. I've seen close relationships evolve in no time. I worked for nine years on the Minnesota study of twins raised apart, and I could

• 19:07Speaker 01

  see these things evolving very quickly between twins who recently met. And I actually had demonstrated this quantitatively. I had identical and paternal twins reared apart. Tell me how they felt when they first met, how they feel now in terms of closeness, and their initial feelings of familiarity and current familiarity.

• 19:29Speaker 01

  The identical twins were significantly higher on most of those than the fraternal twins. But an even more revealing question that I asked, which I'm so grateful I put in, was I asked all the twins, how do you feel in terms of closest of familiarity to the adopted sibling you were raised with in your home? Very few said very close, very, very few. And that's rather counterintuitive. You think, well, I should feel closer to the people I was raised with. It's not so, it's just not so.

• 19:57Chris Williamson?

  So what this counters a little bit is the theory that it's just to do with seeing your mother raise somebody, it's just to do with co-residency during that early years window, because if it was the case, then the way that you look in terms of similarity or personality type, that level of resonance between you and someone that you meet in later life would have relatively limited impact. Also, one thing I've been thinking about, you know, in a modern world where we've got mirrors and we've got cameras and we've got a phone that's got a high definition video recorder in it, we see ourselves. But for almost all of human history, we didn't see ourselves, right? How would we, other people would be able to say you look like them.

• 20:42Speaker 01

  What about, what about lakes and ponds? You could look in there and kind of, it wouldn't be as sharp, but you still had a sense of what you look like. And I know that some of the, some of the older cultures had very shiny glass or metal where they would look, so it's not like today, but you certainly could get a sense of what you look like. Now, I wanted to talk about the thing you mentioned before, so the Western mark effect. All right, so that is very, very fascinating. And I've, I've not documented this, but I have noticed that when identical twins are raised together and both are gay, they're almost never each other's partners. In fact, they have relationships outside the home virtually all the time.

• 21:26Speaker 01

  And that could be a result of, you know, familiarity breeds contempt, if you want to call it that. But there have been, there was a pair of identical twin men raised apart that we studied at the University of Minnesota, and when they met, they became each other's lovers. Now, it's only one case. I went back and looked at the biographical material in previous redeparted twin cases, and there were a couple of cases that kind of hinted at that sort of a relationship. So I wonder if it works the same way. No one has really ever looked at that because the percentage of identical twins in fraternal's raised apart is relatively small, but you could probably do it with siblings. Now, there is a concept in the adoption world called genetic sexual attraction, and it's been

• 22:09Speaker 01

  talked about mostly with mothers and sons who reunite and fathers and daughters. And it's not even that they necessarily have intercourse with each other, but this mother described this feeling that she just wanted this close physical contact. And sometimes this does go into sexual relationships. It can, but it doesn't necessarily have to. Now, where am I going with this? Because I've documented five or six cases of male female twins who've been separated at birth and to meet and marry. And they describe a fierce attraction, probably based on the similarities they perceive in one another. And the way that their relatedness is discovered is because they usually have a child with a genetic

• 22:54Speaker 01

  defect. Because remember that every parent carries a lethal recessive, and if you marry a sibling, or you have, you know, two siblings carry the same lethal recessive, the chance of a child would be 25% if that couple got together. So, at any rate, it's devastating, of course, but some couples split up, some don't. It's very, very interesting. And I also, along those lines, noticed that when we had separated male female twins in our lab in Minnesota, there was absolutely flirtation going on. There's no question about it.

• 23:28Chris Williamson?

  Wow. Okay, so here's a question for you. What does the state think about accidental incest?

• 23:39Speaker 01

  You know, I don't know the answer to that question. But because some of these couples are allowed to marry, and I don't think that they've been from this country, most of them have been from Europe. And far as I know, no one has forced them to separate. If they separate, it's their own choice.

• 23:56Chris Williamson?

  Isn't that interesting? That we almost carve out a exception for the fact that we know there is a very small cohort, but not insignificant, of twins raised apart for one reason or another, fraternal twins. Because that's such a shame. I was thinking, one of the things I wish that you'd been able to work out would have been sexual aversion or an increase in the Western Mark effect if there was such a thing as identical twins that were different sexes. It would be...

• 24:27Speaker 01

  Oh, if they were raised, if they're raised together, I'll bet that's right. But these are twins raised apart where the attraction comes in. Now, I think that that is something we have to worry about, and some countries have started worrying about this. Because now, you know, with all the sperm donors creating so many hundreds of children in some cases, you have to worry that if the mothers live in the same local area, these kids may be about the same age. And so half siblings might get together and they might be attracted to one another just the way that separated twins and siblings are.

• 24:59Chris Williamson?

  What have been, what have been some of the craziest similarities between twins who have been raised apart that you've found?

• 25:07Speaker 01

  Yeah, well, I have to think about these twins, Oscar and Jack, who had the most amazing story. Oscar, they were born in Trinidad to a Romanian Jewish father and a woman from Nazi Germany, Catholic. They were born in 1933. So Nazism was just sort of on the horizon. The marriage failed, and so one boy was raised in Trinidad with his Jewish father, the other raised in Nazi Germany, went to the Hitler Youth. And so when they met, of course, they had very different political and historical understandings. But they both read books back to front. They both used to wash their hands before and after using the toilet. They both thought it was hysterical, sneezed loudly in elevators.

• 25:52Speaker 01

  And they both got very upset if they were in a restaurant and there was a vase of flowers in the middle blocking your view of the other person.

• 26:01Speaker 01

  They used to collect rubber bands around their wrists. I mean, they had a lot of these very odd idiosyncratic matches. And a lot of people think, well, it's coincidence. I don't think so. I think these are hard scientific data. I honestly do. The trouble is, you can't start studying rubber band wearing around the wrist across cases. But what you can study, Chris, is you can study the frequency of these odd similarities in identical versus paternal. And I can tell you that we found them much more in identicals than in fraternals. In fact, in the Minnesota study, we had one pair of paternal twin men, both had 18 tattoos. We counted them. Now, I'm sorry, at this point, we didn't look at the types. Were they flowers? Were they women? What were they? We didn't do that, but we found 18.

• 26:46Speaker 01

  And I actually have a paper that came out earlier in 2022 in the in the premier issue of the Japanese Journal of Twin Studies. And my students and I did this project where we looked at the similarities in twins from the Minnesota study and from previous and past studies. And of course, when a similarity is something like using Crest toothpaste, I mean, nobody cares about that. Half the world uses Crest toothpaste. But we had a pair of twins that used a rare Swedish brand called Vati Makam. And so you have to wonder, you know, what attracts them to this weird stuff? So maybe they like to do things differently,

• 27:27Speaker 01

  or maybe they like the taste. Who knows? Or maybe they have this affinity with Sweden. But the beauty of these kinds of things is that they give you new hypotheses about why you do what you do. For example, we had a pair of fraternal identical twin males who both held the beer can of only Budweiser with their pinky fingernails. Now, why would you do that? It could be because your hand is made a certain way, or you worry about spilling the beer and you want to be very secure about it. You just like the way it feels, something like where you think it looks cool. At any rate, it gives us new ways of thinking about these kinds of things. And let's face it, all of us have odd behaviors that we do that we hope nobody finds out about. But I'm willing to bet you that they're not just there because they're there.

• 28:12Speaker 01

  They're there because of you, because of the way your body and your mind are constructed. And you prefer doing things that way than alternative ways.

• 28:21Chris Williamson?

  Yeah, I uh, I I fear that there's a twin, an unseen twin out there of me doing all of the embarrassing shit that I do private privately and letting other people know about it. I'm thinking about what you spoke about, that these things seem relatively arbitrary. What type of car do you drive? What sort of toothpaste do you use? How many tattoos have you got? But they're very discreet, individual examples that explain an entire suite of traits that somebody has, right? So as you said with the can, is it because it feels good? Is it because that's the particular size of your hand and the can slips out? You've got particularly small hands, particularly big hands or whatever, right? What it shows is a physical manifestation that's very obvious

• 29:07Chris Williamson?

  about uh, that represents something that's going on internally and sort of biologically too. What it suggests is that if we were able to visualize thoughts on some super intelligent fancy FMRI machine in a hundred years' time, the texture of their mind is probably likely to be similar. The sorts of ruminative thoughts that they would have, the things that they wish that they'd said or didn't say, the number of words that they say per minute, the number of ums, ers and likes that they speak. You know, all of this stuff is determined by a combination of your physical attributes, the morphology of your mouth, et cetera. But then also, what's the predisposition that you've got mentally?

• 29:47Speaker 01

  Well, well, sure. I think that all comes into play. I absolutely do. And and I'm not so impressed, as I said, with the common similarities. It's the rare ones that I find intriguing, and those are the ones we focus on. And so, for example, we I did something with names in that Japanese journal, twins, how often they they name their children the same name. And we looked at the frequency of how often names were that name in those years. So, you know, you can start to quantify some of this stuff and get some very interesting findings.

• 30:15Chris Williamson?

  Wasn't the was it the Jim Twins? They have some incredible case?

• 30:20Speaker 01

  Yeah, the Jim Twins did too. Unfortunately, both of them passed away. They're the ones who met at age thirty nine and actually launched the Minnesota study. They lived only forty miles apart in Ohio. And they used to bite their nails. They described a headache syndrome as someone pounding on your head. They used to scatter love letters around the house to their wives. They had work woodworking benches. They drove the same kind of light blue Chevrolet. They vacationed on the same three blocks drift of beach in Florida. Amazingly, they'd ever met. They had they had numerous similarities. And they named their sons James Allen and James Allen. One Allen had an L, two L's, one had one. I know, you can laugh about that. But why would you name what goes into name picking? Obviously, the other partner

• 31:04Speaker 01

  has a saying this too. But maybe because they were first born sons, they wanted to name their son after their own name, very traditional. And or maybe the name Allen reminded them of somebody like the way it sounded. I don't know. I'm just throwing out ideas. But it just gives you a new and fresh way of thinking about these things, not just chalking it up to random chance.

• 31:25Chris Williamson?

  Didn't they have something to do with their marriages as well?

• 31:29Speaker 01

  Yeah. So this was interesting. One of the Jim Twins married Betty and divorced her, married Linda, divorced her, married Sandy. Now, the other one also married Sandy, divorced her, married Linda. If I were Linda, I'd be a little nervous.

• 31:45Chris Williamson?

  Because Betty's coming around.

• 31:47Speaker 01

  If Sandy came into the atmosphere, I'd probably go running.

• 31:52Chris Williamson?

  So interesting. And again, you know, you think about all of the different inputs that we have on our behavior, all of the myriad interactions we've had with the world, the books that we read, especially if we've been raised apart, different books that we read, different whatever, whatever, whatever. And yet.

• 32:09Speaker 01

  They read the same, they read similar books when they're raised apart.

• 32:12Chris Williamson?

  Well, there we go. But it's just this, it's this permanent gravitational pull toward your predisposition.

• 32:19Speaker 01

  I think so. You know, we all have choices in life and we live in, most of us do live in, in communities and cities where there's lots to choose from. And yet there are certain things we choose and certain things we don't. And I think that's why identical twins are alike, because they pick and choose the same things that are compatible with who they are. And, and the very, again, another kind of counterintuitive, but true finding is that genetics, genetic effects seem to go up as we age. And people think, how can that be? It should be environment making more of an impact, but it isn't because once you get away from home and you're not under the thumb of mom and dad anymore, you're free to pick and choose. And that's why the early studies of religious interest showed no genetic effects

• 33:02Speaker 01

  because they were studying children raised at home by their parents. So both twins had to do exactly what mom and dad said. But once they left the house, you began to see the genetic effects kick in because then they would gravitate towards similar types of activities and really express themselves. And sports participation works the same way. Very little genetic effect when you're young at home starts to kick in when you become an adolescent.

• 33:26Chris Williamson?

  Does a, is it IQ is point eight by the end of life, pretty much?

• 33:31Speaker 01

  The heritability is about 80%, 75 to 80%.

• 33:35Chris Williamson?

  Yeah.

• 33:35Speaker 01

  Yes. And this is another one that shows increasing genetic effects as you age because you're constantly refining your interests, your activities, all that sort of stuff that feeds into mental skill.

• 33:45Chris Williamson?

  But you would presume a lot of people, the behavioral genetics deniers out there would say that all of the different inputs you have, your nutrition, your hydration, the amount of vitamin D that you've got, where it is that you live on the planet, the kinds of things you get exposed to, you know, all of these are going to, in their eyes, it would mediate your ability to deploy your IQ. And yet behavioral genetics seems to rule all.

• 34:12Speaker 01

  Well, genetics, no, genetics does not say it's completely genetic. I mean, there's, nothing is a correlation of one. I find the most fascinating thing is that there's so much out there that can make us different. And yet, identical twins are still remarkably alike, whether they're raised apart or raised together. But again, you know, you certainly with nutrition, I mean, if one twin is exposed to a condition, another one isn't, you know, there are cases where one had COVID, one didn't, that sort of thing. So certainly with infections, I mean, there are many things that can make you different, but it's not like it makes you different in every way. You might be different in one area, but very, still very similar in others. I've also had the opportunity to work with twins, identical female twins, where one felt like a male and actually went through surgical reassignment to become

• 34:57Speaker 01

  a male. And yet, the twins were so remarkably alike in every other way, except for this one fundamental difference. And what was so wonderful to witness was just how welcoming the, the non-change twin was. You know, she wanted her now brother to be happy and content, and the brother wasn't for many, many years.

• 35:19Chris Williamson?

  What about, uh, sort of psychopathologies, schizophrenia, depression, anxiety, alcoholism, uh, other sort of maladies like that? What, what is the insights that you've learned with regards to fraternal and identical twins?

• 35:35Speaker 01

  Well, identical twins are more likely to match on all of those than fraternal twins. There's a genetic component in virtually everything you rattled off. Schizophrenia is about forty to fifty percent. It's nowhere near one. The one that, the only psychopathologist that's really, the strongest genetic effect I've seen is autism, at about seventy percent. And that can also vary depending on whether you use strict or looser criteria. But bipolar disorder has a genetic effect. Dementia.

• 36:04Speaker 01

  Breast cancer, interestingly, does not. It's about 20% similarity in females.

• 36:10Chris Williamson?

  Wow, so you could have, you could have identical twins, one of whom does get breast cancer and one of whom doesn't.

• 36:16Speaker 01

  Yeah, that's very, very interesting. You know, this, and see, those cases are extremely informative for the general public. A lot of people think the twin research is only for twins, but it's a model for looking at human behavior in general. And so you could look at a pair of identical twins, and so one has cancer, one doesn't. Why? Why? What about the environment that triggered it in one twin and not in the other? And that's really important information by way of prevention. Diabetes is another one. You know, one twin has it, it's about a 50% match. Multiple sclerosis is another one. Twins, it's funny because identical twins are so alike, but they're less alike than people think they are. Both are really true. I hate to say it, but it is.

• 36:57Chris Williamson?

  What have you learned about twins that are raised apart and BMI or weight?

• 37:06Speaker 01

  Yeah, so it differs from males and females. The similarity is higher for males. With females, there are various hormonal effects, exercise, diet. So females are a little bit more flexible in that way. But body mass index, BMI, does have a genetic effect, as does height and weight separately, yeah.

• 37:25Chris Williamson?

  Yeah, it's, um, that was one of the most interesting things that I learned because a lot of the time, and this gets on to, what is it that you call it? The gene environment covariance?

• 37:35Speaker 01

  A correlation?

• 37:36Chris Williamson?

  Correlation, that's it. Um, that in a household, let's say that you have identical twins. It is very difficult, once both of those twins are in that household, to pass apart, what is the contributing factor of the nurture element here and what is the contributing factor of the nature element here? You see. Fat parents with fat children and you think that that's because of their lifestyle, you know, look at, look at this, but there's a huge genetic component to people's weight and you don't know how I had Robert Plomin on the show. He told me this really, really great insight. I can't forget. He said he has a predisposition to overeat. He said he's a secret fatty. And what he means is that he walks past a bakery and the smell of bread to him is just so alluring.

• 38:21Chris Williamson?

  And he told me this thing and he said, there are many ways to get fat. What he means by that is there are unbelievable suite of different routes toward being any, anything that you want, right? Being conscientious, being industrious, being fat, whatever it might be. It may be that your ghrelin release is higher than typical. That's the hunger hormone released in your stomach. It might be that you comfort eat because of the way that your mental dysfunction is. It may be that you really don't like exercise. You are low on energy. It may be that, you know, pick your myriad of reasons of how people can gain weight. So when you look at people who do gain weight, you presume that it's all from the same root, but it's not necessarily, it can come from places.

• 39:04Speaker 01

  It can come from multiple sources, of course. And see, that's the danger in studying intact nuclear families because you can't separate out the genes and environment. They're all confounded. You know, for example, parents pass on both genes and environments to their children. So if the parents are very bright readers and the child is too, how do you know it's not the genes? How do you know it's not the reading experiences as some combination of both? So that's why you have to apply these developmental designs and separate them out. So one, the very simple one is the classic twin, mono-psychotic or identical twins versus fraternal twins. Another are adoption studies. Twins raised apart, you want to disentangle the genes in the environment. That's what you want to do.

• 39:47Speaker 01

  Many developmental psychologists study parents and children and they come to the conclusion that it's environmental influence, but it's not. It's all confounded. It would be as if I was sick and I took drug A and drug B and got better. Well, how would I know which drug made me better? I wouldn't know. See, it's the same exact thing. You can't figure out what's causing what.

• 40:06Chris Williamson?

  The other interesting thing I always think about this is that because you have a predisposition genetically to be interested in certain things and to behave in particular ways and your children will do too. Therefore, your behavior, which is predisposed by your genetics and your children's predisposition and the environment that your behavior puts them into, all start to exaggerate each other. Now, this isn't to say that children are one to one with their parents' traits. That's not the way that it works. But the point being that when you see particular outliers, I have a friend here in Austin, Aubrey Marcus, the guy that founded Onnit, I'm pretty sure his father was, his parent,

• 40:49Chris Williamson?

  his actual biological father was some inventor guy. His stepfather was a very, very impressive businessman, and that was the person that raised him. His mother was a world champion tennis player. And he went on to sell this business for half a billion dollars at age thirty five. You go, well, it's not, you've got the genetic components. You've got the foundations here and then look at the environment that you grew up in. It's not, it's not a particular surprise that in adulthood, you had a very high bar for yourself, super conscientious, very industrious, worked hard and succeeded.

• 41:22Speaker 01

  Yeah, I know, that's not surprising at all. On the other hand, you know, parents can have two children who are extremely different. And one child might thrive in the environment that's provided by the parents. And then one child will absolutely refuse to go into the family business. So siblings in a family differ by a great deal. And, and the home environment is not the same for all children. The parents can provide all the sports equipment you want, but one child may thrive on it. One child won't even go near it. One child may stay on the computer the whole night and the other child won't go near it. It's, everybody fashions their own environment, you know, within the setting that they find themselves in.

• 41:59Chris Williamson?

  It's not.

• 41:59Speaker 01

  There's so many, there's so many majors we could all be, right? Universities offer tons of different majors, but we pick one or two that are interesting to us. And we, we don't even consider the other ones. Why is that?

• 42:11Chris Williamson?

  It's not strictly.

• 42:13Speaker 01

  And, and I, I have no interest in being a lawyer. My sister, my twin sister is a lawyer, but I have no interest in it.

• 42:20Chris Williamson?

  Is there, have you looked at anything to do with birth order effect? I know that it's not strictly a twin relationship.

• 42:29Speaker 01

  The trouble with birth order is, well, you can have birth order effects with twins, but if the parents treat the first born one as the older, that could have some sort of an effect. With twins, however, you know, if the twins are born in cesarean section and what happens to be a minute old than the other, I think to make a big deal of it, that means nothing. Now, the only way that birth order can make an effect with twins is if it's a vaginal delivery and the first born has a much better situation than the other. Because the uterus changes with the birth of a baby, making it much more difficult for the second child. So that child may have, you know, more adverse influences as a young baby and will need a little more catch up period. So that's where birth order plays a real role.

• 43:14Speaker 01

  But in C sections, it doesn't. And see, I think that a lot of these birth order studies with twins, don't take that into consideration, just lump everybody together and it's ridiculous.

• 43:24Chris Williamson?

  Is there anything that you can learn from triplets that you can't learn from twins?

• 43:29Speaker 01

  It depends on the configuration of triplets. If you had triplets composed of an identical pair and a fraternal, I love that kind of triplets and I've worked with a couple of these because what you find is that the identicals tend to be really close and really similar and the fraternal feels like the odd man out. And I've seen that on many, many cases. If they're all identicals, you know, I mean, it's basically three pairs of twins. So you can match everybody up every which way. And if they're fraternal, you can certainly win a lot too. But I think that the most interesting one are same sex, we are two are identical and one isn't. And what I, if I had to devise an experiment, just pick one up. I would never do this, but I would like triplets like that.

• 44:14Speaker 01

  And I would give away one of the identicals. And I would say, I mean, more like the identical that they weren't raised with or the fraternal. And I bet, you know, my money would be on the identical.

• 44:25Chris Williamson?

  Wow, that would be so interesting.

• 44:27Speaker 01

  Interesting. I'm not saying anybody should ever do it. I don't think twins should be raised apart. So I want to be very clear on that.

• 44:33Chris Williamson?

  Yeah, what's the ethics or how do you feel when, you know, you're observing a lot of these situations? And you have what you've managed to identify in your opinion as the closest human to human bond on the planet? Literally the closest that you can feel to somebody else. And then they get raised apart. So what are your feelings on the ethics and the discomfort around that? And then what happens when twins meet for the first time?

• 45:00Speaker 01

  Well, the ethics are very interesting. And in my 2021 book, Deliberately Divided, I go into that a great deal. And this goes beyond three identical strangers. It's a really in-depth analysis of the Louise Wise Adoption Agency that had a misguided view that identical twins should be raised apart because they grew up with their own identities. And then the secret study that followed these children up until the age of 12, that telling them or their parents that they had a twin. So separating twins for that reason, this misguided developmental theory, I think is unconscionable. Now, I will say that sometimes twins get separated for more legitimate reasons. So maybe a mother dies in childbirth or the family can't afford to keep them.

• 45:44Speaker 01

  But the parents separate them or the family separate them with the children's best interests in heart. I'm still not condoning that, but I do think it's understandable. And twins have also gotten separated through odd circumstances. We had a pair where the twin was visiting her grandmother in mainland China and the other twin was in Taiwan. And because of political developments, they were raised apart. She couldn't go back and be reunited with her family, the one from mainland China. So. These things can happen. Now, my perspective is that, oh, and also, I have a study on the twin children who were separated indirectly through the one child policy in China. And these are twins who are separated partly sometimes because the mother gives away one

• 46:29Speaker 01

  and keeps the other, and then maybe gives the other one away later. Or they're brought together to an orphanage and then somehow they're separated because people don't realize they're twins or whatever. But my view and the view of my colleagues who are in this line of research, we believe in bringing twins together. And we don't believe in keeping them apart for research reasons. In Minnesota, we would sometimes encounter twins who'd never met. And we wouldn't keep them apart, you know, for research reasons, yeah, maybe you want to separate them. We would never do that. In fact, we made an incentive of the study to bring them together so they could spend time together. And we would test them separately. You know, we told them not to discuss the test while it was still ongoing, all that sort of thing. And they took it very seriously. I have no doubt about that. But I'm, I'm completely against twins being raised apart.

• 47:14Speaker 01

  Sometimes private adoptions happen where a mother decides to keep one and give away another one. I mean, I think it's unfortunate these things happen, but I would be of the opinion to never separate twins. I, I just don't think it's right. I think it's, it's a violation of, of a birthright.

• 47:30Chris Williamson?

  What is it like? Have you, have you been there when twins have met for the first time? What's that like?

• 47:35Speaker 01

  I have, I have. It's amazing. It's the most wonderful experience you could ever imagine. And twins do different things. Some jump up and down, some hug and kiss, some just kind of look at each other. Sometimes they, they touch their face and touch their twin's face at the same time. But it's amazing. It's sort of this moment of out of control glee. And you can't help but feel the same joy that they're feeling. After all, most of these people are adoptees who never looked like anybody who raised them. And suddenly, for the first time, they're meeting this celebrated relative, an identical or fraternal twin. And it's a big deal. It's a very big deal. I mean, I sometimes say to people, what if you learned that you had a long lost cousin? Would you go look for them?

• 48:19Speaker 01

  Well, modest, modest interest. How about an uncle or an aunt? Maybe. Parent? Absolutely. Identical twin? You bet. It's, it's irresistible. It's just irresistible.

• 48:32Chris Williamson?

  Why do you think it is that so many people have a problem with behavioral genetic explanations for the traits that we have?

• 48:40Speaker 01

  I think when people hear the word genetics, they feel that whatever that trait is, is nonchangeable and is set in stone, and that could not be further from the truth. Behavior is, after all, the expression of a gene in an environment. And if you modify the environment, you can affect the genetic expression. I will say that some traits are harder to change than others, but you can engineer an environment, you can work harder, you can get into training, you're not stuck with the things. Now, for example, we know that divorce has a genetic component because identical twins are more likely to divorce both of them than fraternal twins. But your genes don't tell you to divorce, you make the decision.

• 49:21Speaker 01

  Maybe you have a difficult personality, or you're very fussy about your partner, or whatever the reason is, but you make the choice. Your genes don't tell you what to do, you are the one in command.

• 49:32Chris Williamson?

  Yeah, I see a lot of this on the internet, especially coming out of the dating sphere, the Black Pill and the incel movement that William in particular studies. You know, behavioral genetics to me was just what, it was the second most fascinating thing that I learned about after evolutionary psychology. And I adored looking at this, not necessarily a conflict, but this tension between my predisposition and the outcomes that I got, what I had in terms of raw materials and then what I had in terms of environment that impacted that. But a lot of people do get fatalistic after learning about behavioral genetics. They believe that they have a very heavily capped ceiling, that it's this sort of deterministic

• 50:17Chris Williamson?

  life that they're living now. I am doomed to be X or Y or Z.

• 50:21Speaker 01

  Yeah, no, that's really not the case. I mean, maybe you're doomed to have brown eyes or hazel eyes, but even then you can get colored lenses if you really want to make the change. But let's face it, I mean, somebody who may be six feet tall will probably never be chosen for gymnastics. There are certain limitations, but I think that's good to know that. You know, it makes us. predisposed toward more realistic decisions and lifestyle changes. So I think I think it's good if you know that, say, your parents are alcoholics. Suppose you learn that. Well, you can use that information. You're not necessarily going to be alcoholic, but you might watch how much you drink, drink a little more carefully, things of that sort. So I think it's it's wonderful information that we can all use.

• 51:00Chris Williamson?

  How do you conceptualize or or explain to people this relationship of genes and environments when it comes to to outcomes in life and and how that should inform our behavior and and the way that we sort of see ourselves and our efforts?

• 51:14Speaker 01

  Well, exactly what I just said, that you can alter environments and affect genetic expression. I give examples of things like that. You know, I'll tell you, the people who I find the most intelligent about this are the parents of fraternal twins and siblings. They know more about human behavior and have a more reasonable view of it than my colleagues, many of my colleagues. They just know that what works for one child doesn't necessarily work for another. And many of them went into parenting, thinking that everything was environmental. And they come out of it with completely different ideas, as do reunited twins. I I interviewed every reunited twin in the Louise Wise Adoption Study.

• 51:56Speaker 01

  And a lot of them said that they really felt that behavior was environmental, but they'd never met a twin before. And suddenly, they're learning about themselves, that their behaviors are not just coming out of nowhere, but they coming out of somewhere. And it's it's a great education. It's just a great education for them.

• 52:13Chris Williamson?

  How much?

• 52:14Speaker 01

  Let me just mention, I I also did a book recently this year on the twin children who survived the Holocaust. It's an annotated photograph collection. I think I told you about that. And these are the twins who were in the Mengele experiments in Ashworth-Sperkenau in 1945. And I went with them to the 40th anniversary reunion in 1985. And, you know, why did these twins survive when some other ones didn't? It's an interesting question. Luck had a role here, too, but a sort of resilience and strength. And the twin bond, too, the strength of that bond gave them each kind of a will to live, which was so important, which non-twin survivors didn't have the benefit of.

• 52:56Chris Williamson?

  Hmm. Thinking about the parenting side of this, how much can rearing change a child?

• 53:07Speaker 01

  Well, I can't give you a number, but what I can say is that I think parents have a very important role, and I think it's different than how people conceptualize it. Parents do not mold you into what you are. I regard parental responsibility as being very sensitive to the child's individual tastes, temperaments, likes, dislikes, abilities and interests. And I think if parents can be attuned to that and really help the child to become more of who they are and to maybe overcome some of their drawbacks like shyness or timidity in some situations, then I think that's a great responsibility. You know, it really pained me when when parents, when mothers who were still pregnant are enrolling

• 53:50Speaker 01

  their children in these prenatal programs of education. I mean, it's ridiculous. I think that that good parenting is really sensitivity to the child and being very supportive and nurturing. So I think parenting makes a huge difference. I think children who grow up with insensitive parents or multiple caretakers who don't take the time to really see what their interests are are the ones who are not going to benefit.

• 54:14Chris Williamson?

  Yeah, Jeffrey Miller once tweeted that every parenting book combined is less useful than one book on behavioral genetics for parents to read.

• 54:23Speaker 01

  I think it's very well put. I would agree with that.

• 54:25Chris Williamson?

  Yeah, it's it's just, I try and look back, you know, I'm an only child, so I try and reflect on my own life and I don't have another, an A B split test of me to be able to look at, to be able to compare. There's some parts of my personality that I do see from my parents, but there is so much that's different, like so much, it's incredible. And I would say that my parents' predisposition in terms of the way that they're set up and the environment that I grew up in was quite aligned. I don't, I don't think that they changed themselves massively when I was born, although obviously all children will change parents, it's a massive life, life switch.

• 55:05Chris Williamson?

  But yeah, it's a, I love the idea of helping a child to find out what is their passion, what is their calling, what it is that that aligns most with them because, you know, for an individual parent to try and reverse engineer or to prescribe in advance, I always, you know, the classic story of the father that didn't get picked for the football team. So, you know, my son, he's going to be the football player and he's two years old throwing a football at Christmas and stuff. That prescriptive role in some regards is good because it creates guidelines that children can follow. But if you're continually having to re-force your child to do that because

• 55:45Chris Williamson?

  all he wants to do is play music or draw or whatever, you're fighting a losing battle.

• 55:51Speaker 01

  Yes, you are. And that's why I think that parents of fraternal twins and near in age siblings are the ones that really understand human development. Because fraternal twins can be extremely different. My sister and I went in very, very different directions. I took ballet, she took drama lessons. We went to different schools, different summer camps that were more suited to what we wanted. And my parents were very good about that. They didn't force us to be together. It was easy. Because children, in their own way, will tell you what's best for them. If parents will only take the time to look.

• 56:20Chris Williamson?

  Hmm, that's a lovely insight. And I think when I first spoke to Plowman about this as well, he, he, the sense that I got, I'm not a parent yet, but the sense that I got from a parent's perspective is that it alleviates a lot of the pressure, I think that parents feel.

• 56:38Speaker 01

  Yes, I think that parents who are less well informed about what parenting is all about, feel they have to do everything. And if they just relaxed a little bit and paid attention and took the cues from the child, I think they'd be a lot better off and they'd be much happier and more effective parents.

• 56:55Chris Williamson?

  Yeah.

• 56:55Speaker 01

  I have no, no qualms about saying that.

• 56:58Chris Williamson?

  Yeah, I think so too. And there is. You know, in a meritocracy, if you are your successes, then it also means that you are your losses too, right? And we know that people have very different, as soon as you take the behavioral genetics pill, like, forget equality of opportunity, forget that, right? Way before equality of opportunity is equality of genetics, which is just not, it's not going to happen between everybody. So as soon as you take that behavioral genetics red pill, what you realize is that largely your child's outcomes in life are going to be determined by the partner that you chose to have them with, right? And you can do things to improve that, you can make the quality of their life better. But if you're,

• 57:41Chris Williamson?

  you know, tiger moming your way to hope that you can create a hundred and forty IQ child, I, it's

• 57:48Speaker 01

  You're going to be disappointed. Keep, keep in mind too, though, that suppose you've got two parents who are very interested in dancing or sports or something like that, they can have a child with absolutely no interest in that whatsoever, because the genes reshuffle in every generation. And, and then also, what's popular in one generation may not be popular in another. And even if a child has a certain ability that aligns with that of the parents, there may be something else that's, that's grabbing everybody's attention in the generation into which the child was born. So these things, you know, have, have all kinds of factors affecting them. Parents and children, I think, are actually less alike than people think they are. We do see similarities, definitely, but

• 58:28Speaker 01

  children are very different. And I think it's largely because they, they had, they get different suites of genetics, and they are in environments and generations where things can be vastly different.

• 58:40Chris Williamson?

  Yeah, I think I'm really seeing this in my generation. So I would be pretty much slap bang in the middle of the millennials. And I would probably guess that aside from some times when there's been global pandemics, like the Spanish flu, or world wars, or Genghis Khan's come through or something, that this block has had from parent to child, the largest inflection point in terms of the difference of environment that we found ourselves in. You know, you have parents that grew up without the internet, children. So for me, I was not internet native, but I think the internet would have come online, maybe when I was eleven or twelve, something like that. So I've got a little bit of time before that, and a good bit of time before smartphones, but relatively digitally native. But the

• 59:23Chris Williamson?

  difference, the difference in my, my dad's upbringing in the sixties and seventies, and mine in the nineties and the two thousands. Is a different universe. So yeah, you know, even if you have, even if you were one to one with your parents in terms of your genetics, look at how different all of the different inputs are that you've got, the, the, the opportunities that you have, the influences, uh, the, the chance to actually display this behavior in a completely different way.

• 59:50Speaker 01

  Yeah, the differences are extraordinary. They are. There's no question about it. And um, yeah, we can't account for everything, but I think we can count, account for a lot.

• 1:00:00Chris Williamson?

  You know what it makes me think about? I have a friend, Johnny, that comes on the show quite regularly. And someone asked a, a question four or five years ago on the show. And they said, if you could go to dinner with four people alive or dead, who would it be? And you know, you've got the, the typical idea of thinking about, would it be Muhammad Ali? And would it be Socrates? And would it be Plato? And would it be Jesus? And Johnny's answer was that he would love to sit down with all four of his great grandfathers. Because he thinks that he would learn an awful lot more about himself from sitting down with them than he would.

• 1:00:34Speaker 01

  Yes. And this is a benefit that the internet has given us, that we can track our families in many ways that other people never could. And there's a real interest in that now, too. I, I regret the fact that I didn't ask my grandfather more questions about his coming over from Russia. I think I would have learned a lot. But still, there's ways of tracking things and, um, and many twins have found each other because of the internet. When, when I was in Minnesota, we thought that we had exhausted every pair of Ritter Park twins in, in English speaking countries. And that was so wrong. It was so wrong. So many have met on the internet by posting a video, not even knowing they were a twin. Just, I, I studied a pair of twins born in South Korea. And one was raised in New Jersey and one was

• 1:01:17Speaker 01

  raised in a very posh French suburb. And the one from, from New Jersey moved to LA. Was an aspiring actress, put a video of herself online. A friend of the other twins saw it and said, you look remarkably similar. And that's what led to their reunion. It's absolutely amazing. And you know, this gets back again to something we talked about a little earlier. I think the idea of finding someone that looks so much like you or is so much like you. Now there are websites for finding people who look like you, these unrelated look alikes. And not only that, there are websites for finding a piece of art, sculpture, a painting, a drawing in a museum that looks like you.

• 1:01:59Speaker 01

  And we don't go looking for something that looks different than us. Children's imaginations of friends were always for someone similar. And I think that's all such fascinating and very revealing information about human nature. People who see identical twins are fascinated. And I think the reason they're fascinated is because we all learn to expect individual differences in behavior and appearance. And so when we encounter identical twins who look so different, it challenges our beliefs in the way that the world works. And it fascinates most of us, but it can still turn off some people who are nevertheless intrigued. Some people may say it's too much closeness, too much similarity, takes away from individuality. But everybody is intrigued nevertheless.

• 1:02:40Speaker 01

  And I think that's why whenever anything happens to identical twins, it's in the news. I mean, it's in the news all the time.

• 1:02:48Chris Williamson?

  These

• 1:02:49Speaker 01

  And I, you know, I get these cases and I get contacts from journalists all the time that want commentaries on unusual cases. And in fact, right now I'm working with the Guinness World Records book on compiling the update instead of twin records, which is a lot of fun.

• 1:03:04Chris Williamson?

  Did you say that you've studied or managed to try and track down every pair of identical twins in the English speaking world?

• 1:03:13Speaker 01

  No, no, I said that, that when the Minnesota study concluded,

• 1:03:17Chris Williamson?

  Yep.

• 1:03:17Speaker 01

  We thought that we had had every pair

• 1:03:20Chris Williamson?

  Right.

• 1:03:20Speaker 01

  In the English speaking world. It was a very naive conclusion because there were so many out there. There were so many people who don't know they're twins. And there were people who didn't have the means to find out if they suspected. But now they do. And there are people out there, fraternal twins, who will never find out because they don't have the advantage of mistaken identity. So many twins meet, I wouldn't say many, but a number meet. Because of mistaken identity, somebody confuses one for the other. You know, and then that's how it all comes about. But fraternal twins don't have that advantage. And so when I think back to that Louise Wise adoption study of twins separated at birth.

• 1:04:01Speaker 01

  Virtually all those identicals met through mistaken identity and the fraternals did not. And I wonder, were other fraternal twins out there who were separated and will never, ever know? And I think that's a shame.

• 1:04:14Chris Williamson?

  It's got me thinking, this is only very tangentially related to your work. I've been thinking for a little while about interracial couples and then the children that they have.

• 1:04:26Speaker 01

  Oh, I'm doing a study on that, but keep going.

• 1:04:29Chris Williamson?

  Okay, all right. So my bro science, not your real science, we can get into that in a second. My bro science was I would be very interested in looking at parental

• 1:04:41Chris Williamson?

  opinions and perspectives on race relations. Let's say that you have a white mother, black father, and then mixed race child. But you know, the gene is relatively dominant, so it's going to be a dark child. So I would love to speak to the mother and, and work out what it's like to be completely uninvested in racial discrimination, personally uninvested, you can altruistically be as invested as you want. And then immediately upon having a child for this to change, and he would be the second one, and this would be the craziest one. If you were able to have the, I can't remember what the name was when you have two eggs that get released and two sperm that go at the same time.

• 1:05:22Chris Williamson?

  But if you, yeah, but if you had that, but those were interracial, that there was, you had a white and a black.

• 1:05:28Speaker 01

  Okay, let me tell you something. I'm very interested in the so-called biracial twins too. And these are fraternal twins that are born to mixed race couples. And I got interested in this because in one of my classes, I had a pair of fraternal twins. One looked very Hispanic and one looked very Caucasian. And they did have a Caucasian mother and Hispanic father. And they told me that their life experiences were extremely different despite being raised at home and in the same communities. That everybody thought that the one who looked Hispanic was a dumb one, when in fact, it was just the other way around. And so there have been many more mixed-race couples lately, and they have paternal twins. And so now I've I've interviewed probably ten, fifteen couples, because I want to understand

• 1:06:13Speaker 01

  the different life experiences of the kids and what the parenting challenges are. And I also am trying to get at the topic of, do you feel a greater kinship with the kid that looks more like you racially than the other one? And that's a very hard concept to get across. I mean, you can't say, who do you love more? You can't say that. But I I wonder if I can somehow tease that out in maybe a less direct way, because it's it's an interesting question. And I also wonder if there is less paternity uncertainty in mixed-race couples.

• 1:06:42Chris Williamson?

  Yeah.

• 1:06:43Speaker 01

  There there might well be. I don't think anyone's ever looked at that, but that's something I can I could think about at the same time. But it's it's really biracial comes from the press and the media. It's not a term that makes sense to me, because they're not biracial. They may look biracial, but they're equally biracial, because they have the same parents.

• 1:07:01Chris Williamson?

  Okay, I understand that. Um, what are the common criticisms that you encounter around twin studies, whether it be methodology, conclusions, pushback, that sort of stuff? What what's most common?

• 1:07:16Speaker 01

  It's probably mostly methodological. People think that when twins are together, they learn from each other, that sort of thing, or they're not tested separately. And I think people, some people think that the conclusions are overdrawn. But I would argue that the critics have not done the studies themselves, and they probably never encountered a pair of twins. I mean, so so many people who have these hard opinions don't have the experience to really make the appropriate judgments. And, you know, and also, so many studies that have used different populations, different subject pools, different protocols, converge on the same conclusions. In in my book, Twenty Twelve, where I give a whole overview of Born Together, Reared

• 1:08:00Speaker 01

  Apart, which is the Minnesota study. I reprint from one of our papers, a graph showing the IQ correlation from four or five different read apart twin studies. One in England, one in Denmark, one in the US, one in Sweden. Different populations, different time points, different protocols, and they all converge on the same basic conclusion about point seven five is the genetic effect. And you, it's rare to get that kind of repetition, replication, I should say, in the behavioral sciences. It's a very robust finding.

• 1:08:33Chris Williamson?

  Yeah, I was gonna say, you know, for the people who like to throw the term replication crisis around and, and point the finger at fields of psychology and social sciences, which is very justified, the two places that you really shouldn't be pointing the finger are behavioral genetics and evolutionary psychology, because both of those.

• 1:08:53Speaker 01

  Lots of repetition there and lots of converging evidence. And, and I, I, I really love that because it's different methodologies and different people, but even if you go outside of behavior genetics and evolutionary psychology, you can see studies done in social psychological theories, and they come out with the same thing, but their interpretations are different. There's a wonderful study done in the 50s where they simply asked twins, you know, who would you miss most in the event of death, twin, mother? And while there was some little variation against my studies, it was basically very remarkable that genetic relatedness was more aligned with higher levels of grief. So if you look in that literature, you still see the stuff. It's just that the interpretation and the theoretical layering is so different.

• 1:09:36Chris Williamson?

  What was their justification for it? What was their interpretation of that effect?

• 1:09:41Speaker 01

  Um, you know, it really wasn't interpretation. It was a sociological study. It was mainly to see what if, what is out there. They really didn't have an interpretation. It was basically what if.

• 1:09:50Chris Williamson?

  Got you.

• 1:09:51Speaker 01

  But the what if aligns with the behavior genetic and evolutionary psychological interpretations.

• 1:09:56Chris Williamson?

  Damn right it does, which is why we're interested in it. Nancy, what do you, you mentioned that just, you've said about the study that you've done. Is your study one of the biggest or the biggest in terms of twins? Or is that Robert Plowman's study that he did in the UK?

• 1:10:12Speaker 01

  Which study are you referring to, Minnesota study?

• 1:10:14Chris Williamson?

  Yes.

• 1:10:15Speaker 01

  Oh, no, the Minnesota study is not my study. I worked on it for many years and I still work on it. That was Dr. Thomas Bouchard, the director, who actually launched that. Now, keep in mind, that was a read apart study. So we ended up with 137 pairs.

• 1:10:29Chris Williamson?

  Yep.

• 1:10:30Speaker 01

  For more identicals than fraternals. Plomin study is twins raised together and he has thousands of pairs. So definitely going to have more.

• 1:10:36Chris Williamson?

  Yeah, I think it was every, every set of twins born in the UK between like nineteen ninety one and nineteen ninety four or something, right?

• 1:10:44Speaker 01

  It's something like that. It's something like that. And, and those kinds of data sets are remarkable. But I will tell you honestly, Chris, that there's nothing I like more than being in a lab with twins and seeing it up close and personal because you really see your data in action. And I think there's no substitute for that. And I remember at one of the international twin conferences, which are held every two years, I organized a film session where I showed films about different aspects of twinship. And I remember some people coming up to me and saying they love seeing this because all they do is work with data. And, you know, I work with data too, a lot of it. But I also work with the real human stuff. And when I bring twins into the lab, I just love it because, again,

• 1:11:26Speaker 01

  just by acting naturally as twins give you all kinds of new interesting ideas and new takes on human development.

• 1:11:33Chris Williamson?

  Did you watch the Netflix documentary, Tell Me Who I Am?

• 1:11:37Speaker 01

  No, I didn't.

• 1:11:38Chris Williamson?

  Nancy, you must watch this.

• 1:11:41Speaker 01

  I'm writing it down now.

• 1:11:42Chris Williamson?

  You must watch it. For the people that haven't seen it, it is, I, I, I wonder if

• 1:11:48Speaker 01

  Is this the one, I think it's more the identical twin men and they had a secret? Is this the one?

• 1:11:54Chris Williamson?

  Yeah, they have a secret. They, one of the guys loses his memory and then he has to be

• 1:11:59Speaker 01

  Right. I, I did see it. I did see it. Yes. And it's remarkable. I, I didn't know that I couldn't remember that was the title. But yes, I did see that. It's remarkable.

• 1:12:07Chris Williamson?

  Yeah. For the people, I won't spoil it. But for the people who are interested in this, Three Identical Strangers, absolutely fantastic film. Born Together, Read Apart, your book, awesome, awesome breakdown of this. And then that, that Tell Me Who I Am is harrowing. And you see, you see, what got me thinking about it was you saying when you're in the lab and you see the twins and so on and so forth. And yeah, on this Tell Me Who I Am, you see these guys reveal this lifelong secret to each other.

• 1:12:39Speaker 01

  Yeah.

• 1:12:40Chris Williamson?

  On set. And it's the first time it's ever happened. It is.

• 1:12:45Speaker 01

  Yeah, it was remarkable.

• 1:12:46Chris Williamson?

  It's crazy.

• 1:12:47Speaker 01

  It was a film that we talked about for a long time. And I will say, there's another film about the Louise Wise Adoption Agency that I think is also excellent, called The Twinning Reaction, which didn't get as much attention as the others. It was made by Laurie Shonseki, an independent filmmaker that came out just about a year before Three Identical Strangers. Also, very excellent, and many of the twins are in both films. You know, when you think about naturalistic observations, one of the best films I've ever seen was done on 16 millimeter, back in the 60s, by my thesis advisor at the University of Chicago. And what he did was, he filmed identical and fraternal twins, once a month over the first year of life. And he looked at their reactions

• 1:13:30Speaker 01

  to strangers. So, in every month, he'd show them with their mother, where they're happy and playing, with a stranger, and maybe with this new toy, and how they reacted to that. And I'm telling you, it was remarkable, because the identicals were so coordinated at that young age, fraternals were so different. It was amazing. It's a beautiful film, and I wish more people would do film. This is something that came up with the conference I was at just last week, the International Society for Human Ethology in Detroit. And it's a shame that more people don't use film. It really is. You can look at it so many times and get new ideas, and it tells things in a way that text just can't.

• 1:14:08Chris Williamson?

  Nancy Segal, ladies and gentlemen. Nancy, I absolutely love your energy. I love your passion for your work. I'm very, very glad that you came up to me at HBS, and accosted me to one side. And I've been looking forward to speaking to you for ages. And I'm super, super excited to see what you do next. Where should people go if they're interested in the work that you're doing? What books should they start with? And what ones have you got coming out? And all the rest of it?

• 1:14:29Speaker 01

  Yeah. So, I have a website with all my twin books and all my related material. And that is Dr. D.R. Nancy Segal, so D.R.N.A.N.C.Y.S.E.G.A.L. twins.org. And I update it very, very often. And I have eight books out now. My ninth one is coming out in August. That's Gay Fathers, Twin Sons, The Citizenship Case That Captured the World. Then I might want to look at my photo book on the Holocaust twins. There's a lot of interesting stories about twinship in there. And deliberately divided, certainly deliberately divided, uh, twins and triples adopted apart inside the inside story, something like that. Uh, but, but if you're really, really

• 1:15:12Speaker 01

  new to twin studies, you might want to check my 1999 book called Entwined Lives, where I cover many, many different topics on twins. I cover the biology, the psychology, uh, reproductive interests, legal cases. I, I work as a, um, an expert witness on, on legal cases, wrongful death, injury, custody, all kinds of things like that. Very, very fascinating. And right now, um, I'm going to be on leave for a year and I'm developing a new book proposal, which is going to be kind of a comprehensive book, kind of the, the tome on twin studies. So I'm excited about it.

• 1:15:50Chris Williamson?

  Oh, yeah. Very cool. Nancy, I appreciate the heck out of you. Thank you very much for joining me today.

• 1:15:55Speaker 01

  Thank you, Chris. I'm glad I accosted you.