In this episode of The Sad Truth, I'm joined by Menno Skilthuizen, an evolutionary biologist and author. We talk about his new book, "Urban Naturalist: How the Urban Jungle Drives Evolution" and the rise of citizen science.
00:02:38.860But when you have people who just come out of their regular jobs and you put them in the field with a couple of passionate scientists, they love it.
00:02:46.840And because their infectious enthusiasm makes us fall in love all over again with our own field of research.
00:02:53.200And that's, to me, I mean, it's great to teach students.
00:02:56.060And, of course, some students are like that as well.
00:02:58.280But with these community scientists, the enthusiasm and the infectiousness of their enthusiasm back to myself is very rewarding.
00:03:07.960Well, you know, one of the things, I mean, we'll dive into this book in a lot more details in a second.
00:03:13.780But one of the things that I think came out in several of your examples that you were describing is the citizen scientists, right?
00:03:21.720This is where professional scientists are seeking the help of everyday people to be able to actually collect the necessary data that they need to collect to complete their project.
00:03:37.500Tell us a bit about citizen scientists.
00:03:39.740Yeah, as you describe it, that is sort of the classical citizen science, which has been going on for a long time, actually, already, because even from before the Second World War, there were the famous project on trying to figure out how great tits, which is the European bird, how they learn to open up milk bottles.
00:04:07.280I just finished that section this morning.
00:04:11.320But that was studied in a sort of a citizen science way, because the scientists were sending out letters to people, and they were putting ads in the newspaper, and people were asked to send in observations of birds doing this and carrying out this behavior.
00:04:26.020So that sort of work, trying to get more data by involving the general public, has been going on for quite a long time.
00:04:33.100It's still on the rise, but in the last 10 years, also in my own work, it's been overtaken by something much more comprehensive, which we call extreme citizen science or community science, where the general public is not just involved in the data gathering part of the research, but they come up with the research questions.
00:04:55.320They come up with finding a method to study it, and the scientists are just there for guidance, for coming up with some ideas, but really the initiative is with the community scientists.
00:05:09.740And that's something we've been trying to stimulate over the past few years.
00:05:15.300That's also something that my new book is largely about, where the scientific process, or the non-professional scientist is involved in the entire scientific process, right from the conception of a question until the publication of the results.
00:05:31.140And that's even more exciting, I think.
00:05:35.940So have there been any studies that have compared the veracity, the methodological rigor, the theoretical sophistication that stems from what you're calling the extreme community scientists or citizen scientists to the standard professional scientists?
00:05:57.540Yeah, there's a couple of people working on this.
00:06:00.320I think Mookie Hackley in University College London has been doing some work on this.
00:06:08.280I'm not exactly up to date on the results of that.
00:06:11.760But in general, of course, the rigidity is less, but often this is compensated by the volume of the data that people gather, because the number of data that large groups of people can gather are so large that the enhanced error that you get in data gathered by non-professional scientists is compensated for by the bulk of the data.
00:06:40.040So you still get a good, often you still get a good statistical signal out of it.
00:06:44.320Now, you meant to say rigidity as a negative thing.
00:06:48.160You didn't mispronounce, you meant to say rigor.
00:06:51.080You really, you meant rigidity, correct?
00:06:55.440No, because had you, that's what I thought you might have meant.
00:06:58.460But had you meant rigidity, that actually would segue to something that I was going to say, which is, so I recently did a, do you know what an X Spaces is on X?
00:08:01.620I find it a bit overwhelming to try to manage the process.
00:08:05.300So usually I only, it's a one-way lecture and people listen and then support.
00:08:09.620And now in my latest X Spaces to the point of rigidity, I was talking about the fact that much of scientific research often misses a key metric, which is interestingness of the research, right?
00:08:27.080You have the methodological rigor and you have the theoretical sophistication, you have internal and external ability, but the end result, forgive me for saying it, is pure bullshit, right?
00:08:37.140We find out that consumers who are, you know, satisfied with the restaurant are more likely to return to the less restaurant.
00:08:46.300Well, who would not have thought that?
00:08:48.600But if you read the paper, it's unbelievably sophisticated and a lot of mathematical symbols and so on, but nobody gives a damn.
00:08:58.360So my view is that probably the citizen scientists are less rigid and might actually come up with more interesting research questions than the professional scientists.
00:09:16.880I can't really come up with an example, but I've noticed the same thing before when you talk to community scientists about some field of research and they come up with suggestions, some of which don't make sense, but some might make sense that a colleague in the same field would never have come up with because we're trained to think in a certain framework.
00:09:38.920And this was just outside of the framework, but it still might help.
00:09:57.460And what he basically does is he offers a framework for how to, I mean, yes, there's an element of personal preferences.
00:10:05.300You may like plant physiology, whereas I'm not interested in this.
00:10:10.020So there is a personal element, but is there some quantifiable epistemological ways by which we could say this is interesting more so than that?
00:10:19.280And to that point, let me give an example in this beautiful book right here, Darwin Comes to Town, of what I would consider that's interesting.
00:10:27.420The study with the butts of cigarettes, whereby the people, you know, well, you tell it.
00:10:37.520Yeah, well, I think that the reason that I find that study interesting and also some other studies that we're doing now with my PhD students is that we've been trained to think of human pollution as pollution,
00:10:54.660as something that is bad, that interferes with animals' lives, and it does, but we are not trained to think in the living environment immediately responding to whatever we throw at them.
00:11:09.880And in this case, this was a study done in Mexico City where house sparrows and house finches were found to have large numbers of discarded cigarette butts in their nests.
00:11:20.720And it turned out that the cigarette butts usually have a little bit of tobacco left in them.
00:11:31.740And we know from previous work that birds often put green plants in their nests, which also have insecticide properties, to help reduce, I mean, that behavior has been selected to help reduce the parasitic mites and fleas in their nests.
00:11:49.960And it turns out that these cigarette butts do the same.
00:11:52.140So they probably pick up the leftover nicotine that's in the butts.
00:12:33.180And that doesn't matter to them whether it's human waste or natural waste.
00:12:37.060And we've now been studying the use of a student of mine, Alco Florian Hiemstra.
00:12:42.620He's studying the use of plastic waste by birds in their nests also.
00:12:49.240And we're also seeing some tantalizing indications that some birds actually prefer to put plastic in their nest.
00:12:57.300Possibly, we don't know exactly if that's true yet, but possibly because they appreciate the same properties that we do in plastic.
00:13:04.860It's durable, doesn't get waterlogged, it's strong.
00:13:08.420So what that also means, and I think that is also the interesting part, sorry if I'm going on too long, but that as soon as we interfere with the environment, it's changed forever.
00:13:23.200And that's also why cleanup projects, if you do them too long after the fact, you're already interfering with an environment that has started to adapt to whatever we're trying to clean up.
00:14:22.060So I can start taking all of the framework of that Davis 1971 paper.
00:14:27.340I think he's got 12 criteria and I can show that on at least two, three, four of these, it's ticking it off.
00:14:34.620So what a wonderful way to teach students how to not just do methodologically rigorous.
00:14:41.680Now, by the way, it doesn't have, for it to be interesting, doesn't have to be counterintuitive always, but it certainly has to make you say, oh, wow, I didn't know that.
00:14:53.240If it does, if all it does is validate my folk psychology, well, sometimes I do have to do that to establish that this is true.
00:15:00.460But in most cases, it's not going to, you know, invoke my imagination.
00:15:07.320It's, it's, I think it's good to, like I said, to prove the obvious sometimes, because sometimes we think something is true without anybody ever having studied it properly.
00:15:18.220But yeah, as soon as you start looking at, at interactions that are more than one or two obvious steps removed from each other, then it gets interesting.
00:15:34.120And then I'd love to go to the genitalia stuff.
00:15:38.020Then go to maybe the links between evolution and evolutionary psychology, because it may or may not surprise you, Menno, that there are many evolutionary biologists who suddenly lose their minds.
00:15:52.340If you apply the exact same principles that they use to study the finches or the tits or the whatever, the salamander, if I apply the exact same methodology, exact same epistemology for human behavior, I suddenly become a Nazi.
00:16:09.500And so we can, we can certainly talk about that, but let's begin with this beauty.
00:16:13.720Tell us the general premise and then we can drill down.
00:16:16.260Well, the general premise is, is that we, again, we're often taught to think of today as a world that's in upheaval, a world that's where, where biodiversity is disappearing, where natural ecosystems are disappearing.
00:16:35.220And those things are all true, but at the same time, I think it's very helpful and in a way comforting to realize that we are also witnessing an event in the history of life on earth that is unprecedented.
00:16:52.180We see urbanized landscapes appearing at an increasing pace at an increasing pace all over the world simultaneously in a remarkably short period of time.
00:17:03.360And these landscapes, these new environments have been caused by a single species, namely us.
00:17:10.620This has never happened before in the history of life on earth, that a single species is able to, to engineer ecosystems all over the world simultaneously with, which share a lot of characteristics.
00:17:20.640And like with all major changes in the environment, we see that the rest of the living world is evolving in response to it.
00:17:29.320So urbanized landscapes, of course, they drive a lot of species to extinction, but they also drive the evolution of a lot of species that do not go extinct, species that adapt to the changes due to either new dangers, new challenges or new opportunities.
00:17:47.760And there's a growing and very interesting field of research that has sprung up just in the past 10, 20 years of evolutionary biologists that are beginning to discover the urban environment as a wonderful scientific playground to see rapid evolution happening of birds and fungi and animals.
00:18:08.820Sorry, sorry, plants and fungi and animals that are all evolving at breakneck speed in response to the changes that we are causing in their environment.
00:18:17.320Yeah. I mean, I, one of the things that I, I think you have several of those examples where you, you know, in the same way that Darwin had the Galapagos Islands, whereby the Darwinian finches are evolving different beak structures, you know, as a result of certain selection pressures.
00:18:34.060Well, you can take Paris that has different micro urban environments.
00:18:40.540And even though the pigeons or whatever the species was, the mole rat or whatever it was in New York, within the same city, there are these little urban islands that are akin to the Galapagos where the singular species becomes multiple uniquely selected species.
00:19:02.020They're not really species yet, but they are differentiating in the same way that's that Darwin's finches must have started differentiating in the beginning because they're locked up in this, in the various green islands of this archipelago of city parks, which they're really locked up in.
00:19:16.460And they're adapting not just because they're isolated, but also because the, the ecology of all those parks is different.
00:19:22.140So in, in central park, this is work done in Fordham university in New York by Jason Munchie South and his team.
00:19:29.200They're really discovering that, for example, in city, in, in central park, the mice have evolved a variant of a gene that allows them to deal with an extremely fatty diet, which is a diet made of junk food.
00:19:41.160And to them, of course, this is just as unhealthy as it is to us, but they have had 400 mouse generations of time to adapt to it.
00:19:48.400And you really see that happening in real time in cities.
00:19:51.860Is there some, I'm, I'm, I'm almost certain you're going to say yes.
00:19:56.100And if, if it's yes, I'd love to hear about it.
00:19:58.140When you look at various species and their capacity to have rapid evolution akin to what you're, I mean, yes, the, the, the, the lifespan of the species will affect that.
00:20:11.500That's why you do the drosophilia flies and so on, because you go, okay, or bacteria or whatever, but is there a mapping that says, here are the types of species that have this very strong innate ability for plasticity versus these other species that are locked in this kind of fixed traits rigidity that doesn't allow them to do well.
00:20:37.440And if so, what are some of the things that differentiate those species?
00:20:41.500Um, it's not easy to, to answer that question.
00:20:47.560Um, also, um, if you're talking about plasticity, so then what we see in cities, the species that do well, and that often also starts evolving as soon as they get into cities are species from, from dynamic environments.
00:21:04.480So, um, from areas that are in nature already quite dynamic and unpredictable and could, and unpredictable, like, like floodplains, for example, um, uh, forest edges, species that live in, in much more predictable and stable environments probably wouldn't do so well in cities.
00:21:23.180And also are not the first candidates that you would expect to start evolving.
00:21:28.120So the whole crow family, for example, are usually, most of those are species that, that live in those dynamic environments.
00:21:34.140And those are also the species that, that do well and that evolve and adapt to, to cities, um, species from sort of originally half open environments, uh, savannah type environments, like the house sparrow.
00:21:47.120Um, maybe even also the house, um, the, the, the, the rock pigeon, which is the ancestor of our city pigeon.
00:21:53.660I think those are all species that are sort of pre-adapted to an environment that is unstable and, and a bit messy.
00:22:01.720And, and they are among the best candidates of urban species to really adapt very quickly and, and, um, become, become urban dwellers.
00:22:11.660So, so basically, I mean, if I wanted to do that study, I would quantify the uncertainty or unpredictability of the typical environment in which the species has evolved, has evolved, give that some number zero to 100, and then correlate that with your ability to adapt in rapidly changing urban environments.
00:22:37.560And I should be able to see exactly the correlation that you spoke about.
00:22:41.040So, I mean, conceptually, it should be a feasible study to do.
00:22:47.080I was just not on top of my head, but that's certainly is a, the way you describe it would for me also be the first way to start, to start thinking about it.
00:22:58.520We'll, we'll come back to the evolution of genitalia in a second, but why is it in your view?
00:23:04.180I mean, I've got my own thoughts on this, but, oh, first of all, have you, are you familiar much with the evolutionary psychology literature?
00:23:14.240I, I, in my research, I don't deal with humans at all, but especially for the genitalia book, I've, I've been, yeah, there's also a bit of human, human genitalia biology in there.
00:23:24.000And I've been dealing with, with some of the literature on, on, uh, human evolutionary biology.
00:23:29.740And of course, it's something that I always get questions about.
00:23:33.280So as a general evolutionary biologist, you, yeah, you're a little bit primed to answer to at least be able to discuss it with some, with some sensibility.
00:23:41.400And, and please feel free to answer any way you want.
00:23:43.940You won't offend me, but are, are you of the, are you part of the taxonomy of evolutionary biologists that is perfectly happy to apply evolutionary biology for every single species except one called humans?
00:23:57.100Or, or even worse, many evolutionary biologists are perfectly happy to apply evolutionary theory to humans as long as it stops at the neck.
00:24:07.500So that opposable thumbs, oh yeah, sure, we'll use evolutionary theory.
00:24:11.660The evolution of the respiratory system, oh sure, evolutionary theory, but don't you dare Nazi to explain the human mind using evolutionary theory.
00:24:21.260And there are some very, very well accomplished scientists, evolutionary biologists who have fallen into this.
00:24:28.400You probably know, I mean, you, your, your book is called Urban Naturalist.
00:24:31.700So you might know the autobiography of E.O.
00:24:40.400No, I'm also of the opinion that's, that there's no reason to, to, to make an exception for, for Homo sapiens in terms of evolution of behavior or, or, or, or, or body morphology.
00:24:54.080I think our, our behaviors, our minds are just as evolvable as, as any other species.
00:24:59.540I think we're, we're quite a special species, but I think we still follow, follow the same rules.
00:25:27.960So the reason why I asked this question, I mean, I, I haven't done a formal study, but I, while there is a general reluctance to accept evolutionary thinking for human behavior, certainly in the social sciences, it is improving a bit.
00:25:43.000But that statement applies more or less somehow in different, you know, ecosystems.
00:25:50.620So for example, France, for whatever reason, has not really picked up evolution.
00:25:54.680There aren't too many evolutionary psychologists in France.
00:26:09.780There's this, I, I wouldn't be able to distinguish between evolution applied to humans and evolution applied in general.
00:26:16.920I don't have any data on that, but I do know that there's this, this study worldwide, or at least it's done in many countries of the acceptance of evolution that's repeated, I think every 10 years or so.
00:26:27.540France is actually very high, usually higher than the Netherlands, because we have a small, but, but quite strong religious minority in the Netherlands.
00:26:36.280So I think we're, we're about 85% at the moment.
00:27:04.240So I don't have any data on the acceptance of evolution, of evolutionary principles applying to humans just as much as to, to other animals.
00:27:13.620I think, yeah, the, the people I talk to, but of course that's not a cross section of the, of the Dutch population.
00:27:22.180I think they would, yeah, they would generally accept, I think like Franz De Waal, of course, is originally a Dutch scientist and he's very well, well known in the Netherlands.
00:27:30.800And I think a lot of people have picked up, or at least well-read people have picked up on his ideas.
00:27:34.760So I think the notion that human behavior evolves, I think is quite well widespread.
00:27:42.040I would say at least three quarters of the, of the country, but maybe that's too optimistic.
00:28:12.240I think he might've been talking about his empathy work.
00:28:17.680And he's got a paper in behavioral and brain sciences with Stephanie Preston, I think, looking at the proximate and ultimate explanations for empathy.
00:28:26.400That's recently come back to my mind because my next book is going to be on suicidal empathy, the, the, the, the miss, the miss application and the miss triggering, uh, of empathy in the wrong context to the wrong targets, which then results in all sorts of insane public policy decisions, whether it be in immigration or criminality and so on.
00:28:50.260And so I, yeah, so people should definitely, uh, check out his work.
00:29:08.880So, I mean, before, before, before I cue you up to, to take over the floor, one of the classic examples that I discussed certainly in my lectures as relating to one feature of genitalia is the famous study across primates showing that the correlation between testes size and the body size of the male of that species correlates to female promiscuity.
00:29:37.880And that species, so that the, the, the, the, the, the genitalia of males is evolving as a adaptive response to female behavior.
00:29:48.600So starting with that, take it away, doctor.
00:29:52.300Well, um, yeah, so the, the, the book, the central message of the, of the book, uh, nature's nether regions is that of all our organs.
00:30:03.800And, uh, with our, I mean, all animals, not just humans, um, the things we use for reproduction are evolving the fastest.
00:30:13.900As you, you see, I'm, I'm interested in fast evolution, fast evolution in cities, but also fast evolution in the nether regions, um, genitalia.
00:30:22.220So if you, if you would, um, compare the shape of the kidneys of a wide range of mammals, they would all look pretty much kidney shaped.
00:30:31.680But if you see then, uh, a graph of all the penises or all the vulvi of those same mammals, they would look wildly different.
00:30:39.860So evolution in, uh, reproductive organs, especially the external ones is occurring at breakneck speed.
00:30:49.320And that's also why, because I'm originally a taxonomist, I'm somebody who distinguishes species, describes species, describes new species, use genitalia to distinguish species that are otherwise very similar.
00:31:00.960So I, I've, I've got a large beetle collection, also a large snail collection when two species are very similar on the outside, you can't really tell them apart.
00:31:09.380If you look at their, at their genitalia, usually the male genitalia, sometimes also the female genitalia, you will always see very clear different differences.
00:31:16.880So it's very easy to distinguish species and on the, on the genitalia.
00:31:20.920And that's because evolution in genitalia is, is, uh, I mean, anything that changes the shape of the genitalia will usually affect reproduction and reproduction is the currency of evolution.
00:31:32.320So any change there is going to have an effect either negative or positively.
00:31:37.780And the, and the, the effect is more direct than other traits that might.
00:31:49.880So really the, the, the, the, you know, the naughty bits of species is, is really the arena where you can find lots of interesting evolutionary patterns.
00:31:59.080So, yeah, I, I really thought since there wasn't a book for the general public about this pretty attractive, but also very revealing, uh, in many, in many meanings of the word, uh, field of study.
00:32:11.920Um, it was really, um, it was really fun to, to, to write an entire book about the evolution of genitalia.
00:32:16.860And there's a lot of literature, but it's all obscure and it's not really been popularized.
00:32:21.920And that's what I've tried to do with that book.
00:32:23.420Does that mind blowing original finding that you started with, which I want to repeat just for me to process it, because that definitely fits under the, that's interesting exclamation point framework.
00:32:35.320So you look at many species, all these species have common organs.
00:32:42.420We, we have eyes, we have kidneys, we have a respiratory system.
00:32:46.580Many of those organs will exhibit homologous features to use fancy bio biological language across species.
00:32:57.680And the ones that exhibit the greatest amount of difference across species are specific to genitalia.
00:33:11.060I mean, even ourselves and, and chimpanzees, we, we, when people, when you would ask somebody, what's the difference between the chimpanzee and a human, they'll come up with brain size and with, with the shape of, of hands and feet.
00:33:24.200But nobody mentions the fact that the chimpanzee penis is, is pointed, doesn't have a glance, has a bone inside, has a little, little, um, sharp spines on the outside, um, that the female vulva swells up, um, that the clitoris is, is, is, is,
00:33:43.600So the number of differences between the chimpanzee genitalia and the human genitalia is much larger than almost any other organ you could, you could see.
00:34:01.260How many species, I mean, we can, we can decide which taxa you want to focus on.
00:34:07.380It's up to you, but how many don't have a penile bone as is the case for humans where you, it's actually a blood flow hydraulic system.
00:34:19.180Like, are there many other species that have that or is it everybody is penile bone with the exception of humans?
00:34:25.500No, I think in the mammals, um, I don't know mammals that well, but the, um, there are certain, certain orders and families where you always find, uh, penile bones.
00:34:35.920I think in squirrels, in, uh, in, in walruses and those groups.
00:34:40.880Um, so it's, it's widespread in various groups and it has been, it has been appearing and disappearing in various groups of mammals as well.
00:34:47.600Um, there is some, there is some literature about why that would be, it's, yeah, it's probably has to do with, with having an erectable penis, uh, at the ready without having to wait for, for a hydraulic response first.
00:35:02.520Um, and that again, depends on, on the ecology of the species, on how large the groups are, how much competition there is.
00:35:09.680So that, that's another thing that the, the ecology and the way of life of a species is, is one of the things that determines what their genitalia will look like.
00:35:17.580Whether, whether, um, yeah, whether it is, there is a lot of competition among males or a lot of competition among females, for example, that depends on the, the density of a species, how rare they are, how easily they find mates.
00:35:29.940And therefore this, this whole competition between sexual partners is what drives the, the, the evolution.
00:35:35.900So we don't find this phenomenon among species that only made once in their life.
00:35:42.420The genitalia are always, always the same, uh, or nearly the same termites.
00:35:47.500For example, these, these termites, Queens, they just made with one male and they are fertilized and they use that sperm to fertilize all their eggs for the rest of their life.
00:35:56.360There is no way or almost no way for, for males to compete with each other or for females to exert a choice between other males.
00:36:05.000So this pure monogamy, uh, creates in the genital region for a very boring, uh, landscape.
00:36:12.920So that actually segues into another question.
00:36:16.220So Robert Trivers, the evolutionary biologist, phenomenal guy, although on a personal level, we might discuss whether he's great or not.
00:36:25.980I've had my little run into him, but, uh, truly, I mean, the stuff that he's done has been unbelievable.
00:36:32.400One of which, and I usually use this example to demonstrate the explanatory power and parsimony of evolutionary theory, right?
00:36:39.700So parental investment theory basically says you want to understand patterns of sex differences within a species, let alone across species.
00:36:47.760Simply look at which, which of the two sexes provides the greater minimal obligatory parental investment.
00:36:55.440And that's going to have all the downstream effects that you could imagine.
00:36:58.980And the way you test that is that you take sex role reversal species where you then see the exact opposite patterns.
00:37:05.400I mean, literally as if, I mean, you couldn't make up the data to be that perfect.
00:37:08.740So is there a similar grand theory that one can use to explain the distribution of genitalia forms across taxa?
00:37:20.920Well, um, it's, so, um, Bill Eberhardt, who was a scientist who has written a lot, he's written a number of land landmark publications about, about the evolution of genitalia.
00:37:37.840Um, and this is really what's, so on the one hand you have, um, females that are, you could say that have different interests from the males that they made with,
00:37:50.280because of course for the, for the males, it would be best if a female uses his sperm to fertilize all her eggs and no other male sperm.
00:37:58.440Evolutionarily that would serve the male's interest best, but for the female side,
00:38:02.360it would be best if she has the ultimate choice of which sperm to use from which males to fertilize, which eggs with.
00:38:07.880So that sets up a conflict of interest during, during copulation, which can drive, uh, on the female side structures that would keep the control on her side.
00:38:18.380And on the male side structures that would override the morphological structures, morphological, but also sometimes chemical structures, hormonal structures, or home hormonal.
00:38:28.700So, um, I mean, there, there are some, yeah, as a side, as a side note, um, so for example, the bed bug is a species where the female has all the necessary plumbing to, to store the sperm of the male and to decide for herself, whether she's not going to use it.
00:38:47.160Um, but at some point during evolution, the male has evolved an ability to override that choice, um, simply by injecting his penis into her body wall and his sperm will completely ignore all her plumbing.
00:39:01.380They will just swim right through her body cavity, right through individual cells, even targeting, uh, the egg cells.
00:39:07.560So the female has lost all opportunity to control, um, what happens when she's inseminated.
00:39:14.200There's also, um, in, in snails, there is, which are hermaphrodite, which makes it more difficult to think about, but they make, they fertilize each other simultaneously in land snails.
00:39:24.720And they inject each other with a, with a dart, with a, really a stone dart, which they made out of, make out of calcium carbonate, which is, um, which is laced with hormones, which trigger involuntary contractions in the organ that is supposed to absorb the sperm.
00:39:42.900So it's actually, if, if, if the dart is injected in the right way in the partner, the partner will absorb more sperm than it would otherwise have done.
00:39:52.840So there the structure is, I mean, the structure is the dart, but there's also the, the, the, the chemical compounds that are injected with the dart.
00:40:00.180So that's one part of the tug of war, but there's a third, a third leg to the three-way tug of war.
00:40:05.480And that's the, uh, competition between males and other males.
00:40:08.840So different males wants to quote unquote want, uh, because this is all an evolutionary process.
00:40:15.560Of course, there's no actual, uh, decision-making process, but different males, um, compete with each other over access to the limited number of eggs that a female can provide.
00:40:27.160And they use evolution has cost structures on males, males genitalia that do not just bypass, do not just target the choice mechanism of females,
00:40:37.580but they also target the sperm of other males, the mating success of other males.
00:40:42.240So there are some males which leave behind the plug in the female genitalia, which prevents other males from mating with her.
00:40:49.480There are some males which scoop out the sperm of previous males before they inject their own sperm.
00:40:56.140The plugs are, um, well, there are spiders, insects, but also, also us, uh, also, uh, primates, uh, produce sperm plugs,
00:41:05.860even though there's, it's not a part of the genitalia.
00:41:08.600So in, in spiders, there's actually an actually part of the penis that is left behind.
00:41:12.760It breaks off and it's left behind in the female genitalia.
00:41:15.880But in primates, um, there are, uh, proteins in the, in the semen, which, um, which coagulate and which produce a, uh, a strong plug.
00:41:27.680And in chimpanzees, which, as you mentioned, are highly promiscuous.
00:41:30.940So there, a sperm plug is really necessary.
00:41:33.660This is really a very tough structure that really plugs, plugs the, um, the, the female vagina on top of the sperm that has been deposited.
00:41:43.120So it's, it's, uh, it prevents what is known as sperm dumping by the female.
00:41:48.800This happens a lot after mating that a female just ejects all the sperm and withholds a chance for it to fertilize her eggs.
00:41:55.540So you, you can, as, as a male, you can prevent that to some extent by leaving a sperm plug behind.
00:42:01.520I'm going to come back to sperm wars in a second, but I just had an idea, which if it hasn't been tested, I see a collaboration in our future.
00:42:10.080Uh, is it the case, so has the distribution of female orgasms bit across species been studied?
00:42:23.320So question one, is that, is, is that a yes?
00:42:37.180So then here is a hypothesis that I'm going to propose, and I'm sure you're going to tell me, sorry, you're 30 years too late, but let's, let me take a shot.
00:42:46.200Uh, I would, uh, posit that the likelihood or the incidence of females having orgasms has to correlate with the extent to which the species is bi-parental.
00:43:02.900Um, because I'm thinking that one of the ways that I establish, I male, that I'm worthy for you to keep me around is that if I am attentive enough to your sexual needs, that I will work hard enough to not just care about my needs.
00:43:19.740And that, that, that is part of a package of the fact that we need to bond long enough as a bi-parental species.
00:43:27.080Am I onto something or am I totally off?
00:43:30.260Um, there, it, it might play a role, but I think all the evidence that I've seen so far points to a more mechanical role for the, for a female orgasm, where by, um, um, vacuum is produced, which, which absorbs, makes the uterus absorb.
00:43:49.720More sperm than if there wouldn't be a female orgasm, so, um, there's, there's actually, it's, it's called the UPSOC theory.
00:44:00.280Um, so, um, so in, in a sense, so the, both things could be at play that, um, indeed it would, um,
00:44:12.360if a male invests a lot in, in raising the offspring, then it would also, uh, be beneficial for him to, uh, to make sure that his sperm is being absorbed and therefore that the female has an orgasm.
00:44:28.640Although I think that would also be true if, if the male wouldn't be investing a lot of effort in the offspring, but then the loss.
00:44:35.780The upsection is true, even if he's not investing, you're saying.
00:44:51.480So I actually, so I've, I've talked about, I've even written about some of his work, uh, and when I lecture about it in class, the students, you have to see their faces.
00:45:16.900And then I asked him, I said, so what's the bottom line?
00:45:19.460And is your, is your research been validated and we can move on or not?
00:45:23.360And, you know, of course, maybe because it's his research, he said that the detractors are not nearly as, you know, strong in their detraction as, as otherwise.
00:45:31.920So, but before I ask you to answer, let me just summarize what the research says.
00:45:36.160It's basically the idea that there are three types of phenotypes that come, come in, in, in spermatozoa, human, human spermatozoa.
00:45:45.300There is the standard one that we think of, which is kind of the fertilizer.
00:45:49.220It's the guys running with the long tails looking for the egg.
00:45:52.720But he argues that there are other types of phenotypes for the spermatozoa, the blockers and the killers.
00:45:59.040The blockers are looking to block entry of incoming sperm, which of course suggests that our female ancestors would have been quite promiscuous since female, since sperm is viable for about 72 hours in the female reproductive tract.
00:46:13.060But the killers are, don't care about the egg, are going to try to kill other men.
00:46:18.560So today, based on what you know, where are we in this?
00:46:22.500Is there greater support for all his stuff?
00:46:27.380For humans and for that specific aspect of what he did, I'm not sure.
00:46:32.620I know that in other species, in mollusks, there's definitely multiple types of sperm.
00:46:37.120And some of those are blockers and killers.
00:46:39.280If it is, if it's been upheld for humans, I don't know.
00:46:45.260I'm not even sure if he had very firm evidence for that particular statement.
00:46:50.560But the work that he did, which I find even more interesting, is the study in which he also investigated whether or not women after having intercourse would dump most of the semen that they had received or not.
00:47:09.860And how that involved how they rated the male that they had had sex with and also whether or not they had an orgasm during sex.
00:47:22.060And that was really a very courageous experiment, which involved a lot of colleagues and students and condoms, which had been donated and returned anonymously.
00:47:32.300And it's really, I think he really did a good job in at least setting the stage for doing that sort of work on human sexual behavior with a very hard biological core in it.
00:47:42.560Actually, I once organized a symposium here in the Netherlands, that's almost 30 years ago now, in which he was one of the invitees.
00:47:52.160So, yeah, I had spent a few days together with him.
00:47:57.380And he was, of course, he, after the scientific work, he did write more fanciful books in which, yeah, the science and fiction was sort of mixed.
00:48:08.560It wasn't really clear which parts were substantiated and which were just fancy.
00:48:13.580But, and I think he's been criticized for that by, I think, by Richard Dawkins, among others.
00:48:27.380Yes, but I think he, yeah, he definitely did a couple of very interesting and very courageous experiments.
00:48:35.900Yeah, one more, one more thing about sperma, then we can move on as we approach the hour.
00:48:41.300I talk about, again, in some of my lectures and in one of my previous books, the study that has looked at, so, polygamy is simply one to many.
00:48:56.840Polygamy, polygamy, I mean, you may know this, but some of our viewers may not.
00:49:00.780Usually people use the term polygamy to imply one man with multiple women, whereas really polygamy just means one with many.
00:49:16.880And so a researcher, a British researcher, had actually done a content analysis of porn movies.
00:49:25.400And you would think, oh, the fantasy of men is, you know, to have a harem of women, and therefore, porn content should be a lot more, you know, one man having sex with multiple women, whereas it turns out, actually, there's a lot more polyandrous situations, one woman with multiple men.
00:49:44.660And so then the question is that that triggers a visual trigger for sperm competition.
00:49:51.000It literally, quote, gets the rise out of you.
00:49:53.240Now, some other researchers came along to test this at the, you know, at the physiological level, if you'd like, or the chemical level, or the sperm level, where, I don't know if you know the study, where they asked men to take one of two images, either a polyandrous one or not a polyandrous one,
00:50:17.020and then return their sample, do you know which study I'm talking about, do you know this?
00:50:25.760Okay, so get ready to experience a that's interesting exclamation point moment.
00:50:30.440And it turns out that the samples returned from the polyandrous images had sperm with greater motility, supporting the idea that it is because of sperm competition.
00:50:49.080So, for example, in animal husbandry, when you want your stud to be inspired, you actually show him, like, he has to see some other mating happening, and then that will kind of get him in the mood.
00:51:04.500And so that, to me, seems unbelievable, no?
00:51:07.600Well, it is, but the work that has been done on the evolution of human genitalia, they tend to support the fact that there must have been periods in human evolution where, yeah, multiple mating in very short periods of time must have taken place.
00:51:26.280There's some evidence that the edge around the human glands, which is also quite unique among primates, that there's actually a device to remove sperm from previous males.
00:52:24.140I mean, again, I suspect you don't, what I'm about to ask you, you don't see as much because you're dealing with animals other than Homo sapiens.
00:52:34.140But why do you think it is so difficult for most people to accept evolution in general and evolutionary psychology in particular?
00:52:43.980It's as if, and I've actually argued this in some of my writings, that it's as if we have evolved to have obstacles against evolutionary thinking for a wide variety of reasons.
00:53:02.740I think we have trouble imagining the vast amount of time that is needed for evolutionary change.
00:53:08.620We're not used to thinking about the accumulating effects of so many generations.
00:53:18.900We think of cause and effect on much smaller timescales.
00:53:22.340So it's very hard to imagine the power of evolution when time is involved and when time is limitless.
00:53:28.100So I think that is one obstacle for us.
00:53:32.180And also in our day-to-day life, we see different behaviors which we can explain in a proximate way much more easily than in an ultimate way.
00:53:44.660Because, yeah, the ultimate way is the way our brains are wired and the variety among them in different individuals.
00:53:52.540And that is the result of evolution and genetic variation over a much longer time period.
00:53:58.000And we're, yeah, we're not used to seeing that as one of the reasons why people do what they do.
00:54:04.920And I think, so for the reasons that you've said and a few others, it gives the false illusion to most people that it is the case that because the ultimate explanation,
00:54:20.680so for those of us who don't know what that means, that's the Darwinian why.
00:54:26.040It feels as though it's post hoc speculation, right?
00:54:30.700It feels as though you sit with a cognac, with a nice cigar, and you just pontificate about just-so stories, void of evidence.
00:54:40.520Whereas, as I've repeatedly explained with great frustration, that the evidentiary threshold that is baked into evolutionary theory is typically higher than is expected in other sciences.
00:54:56.920But yet we're accused of the exact opposite.
00:55:20.080But it is good, I think, always to point people to the evidence and to the publications that show this sort of thing much more clearly than people think it's proven.
00:55:35.300Okay, last question, since we're approaching one hour.
00:55:38.100Please tell us a bit about your next book, Urban Naturalist, and any other projects that you'd like to use this opportunity to promote.
00:55:49.260Yeah, well, Urban Naturalist is, in a way, it's a book that continues where Darwin Comes to Town left off.
00:55:57.780And there is a bit of urban evolution, some new work in the book, but it's much more, the original title for it was how to be an urban naturalist.
00:56:08.160And we decided not to use, it's going to be published by MIT Press, and the editors and me decided not to use that title because it could give the impression that it's a simple manual, a step-to-step guide on how to become an urban naturalist.
00:56:23.680Whereas it's much more about what it is like to be a naturalist, an old-fashioned, exploratory, inquisitive, curious naturalist of the Victorian style in a modern setting, in today's world, where the most fascinating kind of biology is happening in the urban realm.
00:56:46.520Where you could be a Victorian explorer in your own streets, discovering completely new stuff, new behaviors, new natural history, new evolution that hasn't been documented before.
00:57:00.560And the nice thing is that, in a way, science has come full circle.
00:57:05.280I'm trying to advocate if people start doing what I'm describing in the book, then science has come full circle in the sense that in the 19th century, in the early 19th century,
00:57:14.940there was no such thing as a professional scientist.
00:57:18.620The scientists were people who had, for some reason or other, time and curiosity to be independent explorers of their environment.
00:57:28.940And they were publishing and reading their papers to their like-minded friends.
00:57:34.720They didn't need much to do interesting discoveries.
00:57:37.820Darwin just had his greenhouse and his wormstone in his garden, and that's where he did his work.
00:57:42.220But then came the 20th century, and that sort of individualistic discovery was no longer possible.
00:57:49.980You needed large institutes, a lot of money, large libraries, large labs full of equipment.
00:57:55.640So the amateur was sort of cut out of the scientific world for most of the 20th century.
00:58:01.700They were dabbling in the fringe, but they were not making important discoveries.
00:58:05.260And I think now the time has come for non-professional scientists to start making interesting discoveries again, because you don't need those large labs.
00:58:42.340I've also designed one on evolution, which has thousands, tens of thousands of students, larger numbers than I would ever have reached in my university classes.
00:58:52.700So everybody can benefit from university level scientific training.
00:58:58.460And I think to be an explorer of your urban world really helps you to find new value in living in an urbanized world.
00:59:11.260Because most of today's people, and later in the century will be an even larger fraction, will be living in large urbanized conglomerations and never have access to wild nature anymore.
00:59:23.600So if they want to be a naturalist, they can become a naturalist in their own street, in their own neighborhood, team up with neighbors who are also interested in science and in flora and fauna,
00:59:35.080and really create new value for living in an urban environment, which most people think is completely devoid of nature.
00:59:44.020But I think it's really the other way around.
00:59:45.680And you can really enjoy the same pleasures that those early Victorian explorers did in today's modern cities.