 So, welcome to the third episode of what sex got to do with it. I'm here with Heather Remoff, the author, and she is my favorite great-grandmother in Arlington, and so we're on to chapter two because we started with the acknowledgments and this chapter is called Why Now? So do you want to give me a little explanation for why that title to the chapter? Yeah, the chapter actually, why did I write this book now, is I suddenly became so concerned about climate change. I have great-grandchildren, as you mentioned, and climate change, the concern about how rapidly climate apocalypse is approaching made me think. Heather, you have ideas about our human species-specific traits that if we could employ them, we might be able to design policies that could address climate change. And so I had that sense of omission, that's why I wrote the book now. Now, why now in terms of Darwin? Hundreds of books have been written about Charles Darwin, but I'm very, very much aware that his theory of sexual selection, which was outlined in his book The Descent of Men and Selection in Relation to Sex, that his theory of sexual selection is in need of a serious, serious update. It's not accurate. I understand. But so that's why now the book, but the chapter, was there a specific reason for why you call chapter two Why Now? Yeah, in part because why does this matter now? And one reason in terms of the way men and women relate to each other on a very small, personal level, not everyone is completely happy with how their relationships are going. And then zoom out to the larger picture is I am concerned about climate change. And I think it's time to take a second look at Darwin, which, as I was explaining to you earlier, I think is really hard to do for a reason that I just learned about, a term called anchor bias, which means that the first thing we learn about a subject gets lodged in our brain. And it's the most difficult bias to overcome. And everyone has heard Darwin's theory of sexual selection presented in a way that I don't think is an accurate description of how sexual selection really works. And so I'm eager to update that. Right, right. And to emphasize, I mean, the book is called What Sex Got To Do With It, and I love that you just used the phrase zoom out because I did want to compliment you on a great piece of writing, which was on page 27 of the manuscript to me because I read the manuscript and not the book and it says consider our sense of economic security or more accurately insecurity. It is perhaps only individuals in the wealthiest top 10% who express satisfaction with their status, zoom out, which you just said, move from the personal to the global and consider the worldwide increase in inequality. Now raise the curtain on the Anthropocene. I thought that was just a great piece of writing, to zoom out in the race of curtain. So you definitely have a flair when you write it. So now I think it's going to be the heart of our discussion of this chapter of two and you talk about how women, when you talk about, you mentioned how you had talked to, I guess, 66 women, and you said that none of them or is very aware that a woman would have sex with a man unless they're dying out together. And you relate this to how the courtship is a part of the sexual selection or less the sexual selection process and food courtship seems to be one of the most important or most common elements of courtship. And so I found that intriguing. So I guess it's because food is just so important to survival. To survival. Right. Lynn, I'm fairly certain that I'm the person who documented courtship feeding in humans. It's been acknowledged by biologists in all other species. I mean, a friend recently sent me a photo he'd taken of a male cardinal feeding a female cardinal sunflower seed at his bird feeder. And that's courtship feeding in birds. And we've always acknowledged that courtship feeding exists in other animals. But it's not been documented in humans. And you can say, well, of course, part of the dating scene involves going out to dinner together. But it really goes beyond that, beyond that cultural, although that cultural, having a meal together amplifies it. When I was interviewing these women, I didn't take notes. And we just did open-ended discussions. I asked them to talk to me about the men in their lives, how they met, what traits made them attractive, just, and women will talk about the men in their lives. Those interviews ran from three to five hours in length. And it was on the tape recorder. I didn't type at the time, so I paid someone to transcribe my tapes. And one of the last interviews, I was at the very end, and the woman described her husband as the sexiest man alive. And I thought, wow, that's pretty high praise. I said, what traits inspired you to give him that description? And she was so embarrassed. She couldn't think of things. She kept saying, oh, oh, oh, I can't think. Oh, wait, give me a minute. And then suddenly, she looked up and smiled and said, oh, I know. He brought me two fresh pineapples. And at that moment, I pictured courtship feeding in other species, where the male's presenting the female with a gift of food. Now, I had coded most of my interviews by then. I'd gone through and color marked various traits that women described. And that was coming up with profiles. But I had nothing in it about food. And once she had done that, I went back through all my old notes. And discussions of food were everywhere. But it wasn't just, oh, we went out for dinner. You know, at the time that they were telling me, I thought, oh, yeah. It's nice that you had the shrimp scampi and a Caesar salad. But I kind of stopped paying attention. But the tape recorder was still paying attention. And those descriptions of meals that might have occurred 20 years before the significance of them were that was the meal they had together or what he fed her immediately before they had sex for the first time. So it was very, very much tied to that, to sort of a reproductive intent. In fact, when I wrote my first book, Sexual Choice, one of the men's magazines did an interview with me around Valentine's Day. And the hint that I gave was if you have only $5 to spend, don't spend it on flowers. Spend it on food, OK? So courtship feeding. I do think I'm the first to document that in humans. So now I have a question that kind of popped in my head. Since we're all, this is all about sex, I'm not going to worry about the delicacy of the question. OK. Are you going to make me blush? Well, it just might. So do women's appetite for types of food change with respect to where they are in their cycle? That I don't know. I could not enter that question. But what about your history? Well, some people describe craving chocolate, et cetera, before they ovulate. But I don't have sound data on that. I do know that women's self-esteem goes up prior to ovulation and during ovulation. And in fact, because I interviewed these women at a rare moment in time that will never occur again. The sexual revolution, the quote unquote sexual revolution, it happened. This was in the mid-70s. AIDS had not yet reared its ugly head. And so most contraceptive use was really pregnancy prevention. It wasn't so much. And also, everybody assumed, oh, antibiotics will cure any STD that wears its ugly head. So I interviewed women about contraceptive use with their various male partners also, because I was curious. My assumption was that they'd be more risk-taking with sex with the man that they felt would make a desirable partner. In fact, quite the opposite was true. They became careful users of birth control only when they met a man that they would have liked to father their children. So birth control use was more a matter of timing than it was of anything else. It's not that they didn't want that. It's like they didn't even think of themselves able to get pregnant until they met a man who made them want to have children. So that goes back to the high self-esteem at ovulation, because I thought, gee, some of these women had sex, what I called sex with jerks. Some of these women had sex with jerks and didn't get pregnant. Why is that? Why did that happen? I'm not advocating the sex with jerks theory of contraception. I don't want any of my kids or grandkids or great-grandkids to employ that method. But what I suspected might be happening was the high self-esteem that a company's ovulation meant that women would be less likely to have sex with a jerk at the time they were ovulating. That's a theory, not been proven. See, I have a theory for everything, Len. But that one's not been documented. But the sense of high self-esteem during ovulation has been documented, as has cravings for chocolate and stuff. But I don't know enough about that. That's fine. And we're going to circle back into that in a later chapter. I mean, so I'm going to kind of move the conversation along a little bit, but I'm still going to stay on the food thing because you mentioned how I think it is with the guppies. I mean, they dine on orange fruit. And so you say there's no surprise that the females find orange such an attractive feature in the coloration of the males that they favor. So let's say something happened pretty dramatically. And oranges were no longer available. Let's say apples were available and they're red apples. And so now only to survive, you need to consume red apples. Do you think the color of the features in the males they favor would change to red in a pretty short order? I'm not sure. I suspect that it might, but I don't know. Because I do believe, as you know having read my book, that evolution can happen much more quickly than Darwin gave it credit for. That's one of my quarrels with Darwin is that he believed it was very, very slow. He took large numbers of offspring. I think he's wrong in that. And one of the gentlemen I think I talked about maybe in this chapter or the next who worked with lizards documented how rapidly evolution can occur. Yeah, and I'll relate a story about my past with some respect to selection experiments. And there was a poor selection, sexual selection involved. Although it was just, well, I shouldn't even say sexual selection involved, but it was male-female mating. So I did some research with a graduate student, his name is Ken Weber, me, and what we were trying to test is whether small populations would evolve more quickly than large populations. And at the time, there were two schools of thought. One is that the small population and the mutation would be spread through or variation. A allele with a positive effect would spread through the population much more quickly because it's a small population. And the other theory was that, well, with a large population, you'd have more variation. And so even though a positive allele would spread through the population more slowly, because you'd have a greater variation, you'd have a better chance of a allele that was even more beneficial arising. And so we tested for resistance to alcohol. And so we had a column of ethanol gas. We put flies at the top of it. They just baffles, they could fall down. So the longer it took them to fall down, the more tolerant they were of the alcohol. So we would take the ones that fell down last and we found our next generation on those. And so we had two different sized populations. One were 100 fruit flies and the other were for 1,000 fruit flies. And it started off with the smaller population having a greater resistance. The way we measured the resistance was by how long it took all the flies to fall down so we just take the average. The smaller population started off with a much greater resistance to the large population. But by the 25th generation, the large population caught up and it never looked back. I mean, so by like 100 generations, I mean the larger population was so much more resistant in ethanol than the small population. Oh, that's fascinating. Yeah, it was a fascinating experiment. And so, and yes, that's when I became really familiar with the Hardy-Weinberg equation, equilibrium. And clearly we were forcing it because we... They weren't test tubes and so forth, yeah. Right, right, right. But still it's a fascinating study. Yeah, yeah. So yeah, it's just an indication of how quickly selections can act me but also the benefit of having a larger population versus a smaller population. Even though in the short run, it seems like the quality population is better off. I mean, in the longer runs, I mean, if you're really selecting for a given trait, the more variation you have, chances are, I mean, the more quickly you... Well, the more variation you have, the more likely you'll get a really strong allele that's beneficial for the entire population. Yeah, sexual selection is really good and that it hides some traits, you know, that all the traits that are expressed are not all the traits that are available. And so it can adapt quickly. Sexual selection enables species to adapt much more quickly than asexual selection does. And there are some species. There used to be what is called the Elm Oyster model, do you remember, do you have any familiarity with that? I think both Elms and Oysters can switch between... Between sexual and asexual selection as a form of reproduction, depending on what the environment around them is. So in times that are favorable, they go with asexual selection because they're already well adapted to that. But when times are tough, then they'll switch to sexual selection because more varieties available. And hopefully some of their offspring will have genes expressed that enable them to survive in that tougher climate. So that sort of relates to the study you're talking about with the fruit flasks. I find it all just completely fascinating. No, I agree, you know, and so it is interesting, you know, so what you talk about in this one, where we had the event that led to the reduction in chromosomes in the great apes from 24, meaning to current humans, 23, and you say, it's a seemingly small change, you know, and for me, I guess, my background in biology, it's like that's a huge change, you know, and so the reduction by one chromosome, I mean, it's massive, you know, and so you do actually point out, it's like, how is it then that chances are you wouldn't end up with a species or an entity that would be able to mate with another one and then produce fertile offspring? And so you raise the possibility that other mutations, similar mutations were happening at the same time, because we were at a point where there may be lots of environmental background that's my speculation, I mean, obviously don't know, but that is a massive change. You know, the whole motion of species is such a slippery definition. We don't have, I don't think we have a consistent and reliable definition of what a species is. My favorite definition, the one that I cling to is different chromosome numbers. You know, for example, in some of the fish that evolve very quickly to different color variations, we might call those a different species, but in fact they still have the same chromosome numbers and if there's nobody else available, they can and do mate with each other. So, and I know there are behavioral barriers to mating, sometimes such as a bird doesn't recognize the song, but as long as the numbers of chromosome pairs are the same, I consider them the same species. But species, we don't have a good, at least not a hard and fast definition that satisfies me and I once tried to raise the question with a bunch of mycologists who were talking about different mushrooms and their reproductive habits are kind of amazing anyhow and they laughed at my question and they said, oh, oh, you're hinting at something, you're suggesting that our definition of species is a little slippery. I said, yeah, they said, you're right, it is. So, yeah, to me, that is the origin of our species. This end-to-end chromosome fusion, almost overnight, we went from a species with 24 pairs of chromosomes as all the great apes have to one with 23. And that's the origin of our species and it happened fast. But it's not necessarily a given though that they weren't able to mate with the other. It's hard to come up with examples of species that can mate across different chromosomes pairs and come up with fertile offspring or even come up with viable offspring. I mean, we're all familiar with the horse and the donkey resulting in a mule. That's one of the species, two species that have different chromosome pairs, horses and donkeys. And they are able to mate with each other and produce viable offspring, but those offspring are themselves sterile, they're not fertile. And of all the species, look at how few examples we have of that happening, of cross-species mating that come up with viable offspring at all. You know, most cross-species mating don't produce viable offspring in most cases. So then your hypothesis for why it might have been that the species was able to take off, the new species was that there was, there were other mutations happening. So you got like the same mutations or at least mutations that created that reduction in chromosomes happening in multiple places. And what was the other possibility? All right, I don't remember. I don't remember either. But maybe even like mating back to the parents or within the family group that, I mean, I'm just making this up as we go along here then where there'd be the same vulnerability. I do speculate and I know this is true that not all chromosomes are created equal. That was the other thing you said. Yeah, so some chromosome pairs are, or some chromosomes are more vulnerable to mutations than others. But most of them are the result of what we call non-disjunction, like horizontal. But this reduction in chromosome pairs is the result of end-to-end chromosome fusion. And that's much rare because the telomeres at the ends of the chromosomes protect that from happening. And there are some chromosomes much more vulnerable to non-disjunctions such as Trisomy 21, which results in Down syndrome. If it happens often enough, then the syndrome gets named but some of them happen so rarely because some chromosomes are less vulnerable to that kind of what's called non-disjunction where they don't cleanly separate. Right, right. So yeah, I guess maybe I can see what happens is that you have that end fusion happening frequently enough and given the argument that you make later on that people with similar genetic compositions are attracted to each other, you could get the species going that way because, all right, all right, I was just trying to get to how I was thinking, that we then, yeah, I was thinking, was it a bottleneck around that time also? I don't know, Len, you might know that better than I do. No, I know, I'm really bad at that. That was not my forte when it came to my working population evolution today. I mean, it's like remembering the species and all that. I was just really more of a DNA sequencer being and doing these kinds of selection experiments, you know. I just find it also incredibly interesting. It's not everybody's cup of tea, but it's something that I find just fascinating to try to figure out how did this happen? And I am increasingly convinced that some of it happened rather rapidly, just like the whole Cambrian explosion that we hear about, how do we explain the Cambrian explosion? Well, guess what evolved shortly before the Cambrian explosion? Sexual reproduction, as opposed to asexual reproduction. Sexual reproduction is just, evolution happens much more quickly because of this scrambling. Yeah, exactly, right, recombination. Yeah, and recombination. So, I just, you know, that's just fun to talk about with you. And as much as we want to keep going, I'm gonna do the editors a little favor on this one, and we're gonna end it a little early, because I think one of the last two ran it all along, so I'm gonna end up, I'm gonna sum it up, as you say. If I could sum up the difference between the 66 women that I interviewed and the ways in which men respond when I asked the same question, it would be that women come to see the men that they've come to love as handsome, whereas the men come to love the women that they have first, excuse me, the first received as beautiful. I guess that does sum it up, huh? So, so. And as I say in the book, that one of Darwin's mistakes is he projected the trait that influences male desire, beauty. He projected that trait onto the women doing the choosing, where in fact women choose for a whole range of traits other than physical appearance. Once they've chosen for others those traits, they see the guy as handsome. But, yeah, it's fun. No, no, it is, he's also so, and we're gonna continue to fun on chapter three in our next episode, so thank you for a wonderful conversation. Excellent.