[00:00:04] Speaker A: Id the Future, a podcast about evolution and intelligent design.
[00:00:12] Speaker B: Welcome to id the future. I'm your host, Andrew McDermot. Today I'm speaking again with Dr. Jonathan McClatchy, fellow and resident biologist at the Discovery Institute's center for Science and Culture. Jonathan was previously an assistant professor at Sadler College in Boston, where he lectured biology for four years. He holds a bachelor's degree in forensic biology, a master's degree in evolutionary biology, a second master's degree in medical and molecular bioscience, and a PhD in evolutionary biology. His research interests include the scientific evidence of design in nature, arguments for the existence of God, and New Testament scholarship. Jonathan is also founder and director of Talkabouts.com. Jonathan, welcome back to the podcast.
[00:00:57] Speaker A: Great to be here.
[00:00:58] Speaker B: In a previous episode, we discussed an article you wrote for evolutionnews.org some years ago that explained why sex sexual reproduction is the queen of problems for evolutionary theory. The origin and maintenance of sex and recombination is not easily explainable by evolutionary processes. Popular science writer Carl Zimmer has written that sex is not only unnecessary, but it ought to be a recipe for evolutionary disaster. And yet sex reigns despite the short term disadvantages. This is a problem when it comes to attempts to explain sexual reproduction in evolutionary terms. We also talked last time about the design and complexity of sperm cells and how they challenge evolution and provide evidence of intelligent design.
In this episode, we're going to continue discussing this topic with a look at two more of the irreducibly complex core of components needed for successful sexual reproduction, seminal fluid and sperm capacitation. And we'll also talk a bit about the principle of irreducible complexity itself, what it means, a rebuttal of arguments made against it, and even how a bayesian approach to irreducible complexity, using bayesian reasoning can help us understand it better. All right, Jonathan, let's start with seminal fluid. Now, recalling high school health and science class, many of us know that between 200 and 500 million sperm are released with each ejaculation. Why are such huge numbers necessary? Sure.
[00:02:28] Speaker A: Well, such huge numbers are needed in order to have a significant chance of fertilizing the egg, because many hazards confront the sperm cells as they make their way through the uterus and the uterine tubes. So after ejaculation, millions of the released sperm cells can either flow out of the vagina or else die in its acidic environment. And the sperm cells also need to pass through the cervix and opening into the uterus, which requires passage through the cervical mucus. And although the mucus is thinned to a more watery consistency during the fertile window. Making it more hospitable to sperm. There are millions of sperm cells that die attempting to make it through the mucus. And moreover, the female reproductive tract has immune defenses that protect against pathogens. And these defenses can also target and destroy sperm cells, which are viewed as foreign cells. And antibodies can recognize the sperm.
And that can lead to their inactivation or their elimination. There are also tiny cilia in the fallopian tube. That propel the egg towards the uterus. And some of the sperm that are left end up becoming trapped in the cilia and they die there.
There is only a small handful of the original sperm cells. That actually make it as far as the egg. And so it is in fact needed for there to be hundreds of millions of sperm cells. That get released with an ejaculation. In order to have a reasonable chance of one of those sperm cells making it to the egg and fertilizing it.
[00:04:09] Speaker B: Yeah. So one in 200 million or 500 million chance. A harrowing journey for these sperm cells with lots of things to overcome. But we see how the process does make things easier. Now, the seminal fluid is very important to the success of fertilization. Let's review some of the ways that seminal fluid helps the sperm cells in their life or death journey. First, it's an energy source. Tell us about that.
[00:04:36] Speaker A: Well, the seminal fluid provides essential nutrients. To support the survival and the motility of the sperm. So that would include fructose, which is a sugar that serves as a source of energy for the sperm. It fuels the production of atp in the mitochondria. As well as other sugars and amino acids and enzymes. So if there wasn't fructose in the seminal fluid to power the mitochondria, that would have significant implications for the motility and viability of the sperm cells.
[00:05:15] Speaker B: Okay, next, the seminal fluid is alkaline. Why is that helpful?
[00:05:19] Speaker A: Yeah, so this is important because the vagina has an acidic ph, as I mentioned before. And that's produced by the normal flora or bacterial populations that are present in the vagina. And this environment is unfavorable to the sperm cells.
And so the alkalinity of the seminal fluid actually serves to neutralize the acidic environment of the vagina. And this actually assists in the survival of the sperm cells.
[00:05:50] Speaker B: Okay, now a couple more really key features here. The seminal fluid has the ability to coagulate and liquefy. Why is that important?
[00:05:58] Speaker A: Well, following ejaculation, the seminal fluid initially coagulates to form a gel like consistency. And this coagulation helps to keep the semen in the vagina and the cervix. It prevents it from immediately running out and thereby greatly increasing the ods of a successful fertilization. So this occurs upon exposure to the air or the alkaline environment of the female reproductive tract, activating clotting factors that are present in the seminal fluid, including tissue transyclotaminase. So the transclotaminase converts the seminogellin, which is a major protein in seminal fluid secreted by the seminal vesicles, into a sticky protein called fibrin. And then fibrin forms a network like structure that entraps sperm and other components of the semen. And if the semen were to remain in that condition, the sperm would be immobilized permanently and they wouldn't be able to fertilize the egg. But over time, the coagulated sperm actually liquefies as a result of enzymes that are present in the fluid. And these enzymes slowly break down the fiber network, and this allows the sperms to move more freely. And so there's a paper that was published in Journal Biology of Reproduction in 2020 that notes that, and I'm quoting, the liquefaction process is crucial for the sperm to gain their motility and successful transport to the fertilization site. In fallopian tubes, or oviducts in animals Hiber viscous semen or failure in liquefaction is one of the causes of male infertility, end quote. So, in fact, targeting these serine protease has actually been suggested as a target for novel non hormonal contraceptives. So it's crucial for the process of fertilization.
[00:07:53] Speaker B: Interesting. And from my reading of your work, the coagulation and liquefaction, or liquefication properties of seminal fluid pose a challenge to evolutionary explanations. Why is that? Yeah.
[00:08:05] Speaker A: So, from an evolutionary perspective, it's difficult to envision a scenario where semen coagulation evolved without simultaneously having a mechanism in hand for liquefaction.
So this is a prime example of a nonadaptive intermediate that is prohibitive to evolution by natural selection.
[00:08:25] Speaker B: Well, let's move on to sperm capacitation, a significant prerequisite to fertilization. Capacitation means the changes sperm cells have to undergo in order to give them the ability to fertilize an egg. Let's start with the biochemical changes.
[00:08:39] Speaker A: Sure. So sperm capacitation occurs in the female reproductive tract, and it prepares the sperm to interact successfully with the egg. And it's absolutely fundamental in order for the sperm cells to acquire the ability or the capacity to fertilize. So upon initial ejaculation of the sperm, they possess certain molecules and proteins on their surface that inhibit their ability to fertilize an egg. And so these surface molecules during capacitation get removed. That would include cholesterol and glycoproteins or modified, allowing the sperm to become more receptive to the egg.
[00:09:22] Speaker B: Okay. And sperm cells also undergo physiological changes during this process of capacitation. Can you outline those for us? Sure.
[00:09:31] Speaker A: So as the capacitation progresses, the motility pattern of the sperm also changes, so they undergo hyperactivation, which is characterized by increased amplitude and asymmetrical beating of the tail.
So hyperactivated sperm exhibit vigorous movements, which help them to navigate through the female reproductive tract and arrive at the egg cell.
And capacitation also involves changes in the composition and fluidity of the sperm cell membrane. And these changes allow the sperm to interact better with the zona polucida of the egg, which is the outer shell, if you will. And the acrosome becomes a prime for the acrosome reaction, which releases these enzymes that we talked about in the last program to allow penetration of the egg membrane. And capacitation is also associated with an increase in the influx of calcium ions into the sperm. So calcium plays a crucial role in various intracellular signaling processes that are necessary for sperm function and fertilization.
[00:10:33] Speaker B: Okay, now, in your article on these components of sexual reproduction, you conclude with this. Various features of the head, middle piece and flagellum, together with the properties of the salmonell fluid, are critical to the sperm cell's function of reaching and fertilizing an egg. If any one of these parts is not present or fails to function properly, the sperm cell is rendered completely impotent and reproduction cannot occur. So I wanted to take this moment to kind of talk about irreducible complexity a bit more. Now, the term was coined by biochemist Michael Behe in his 1996 book Darwin's Black Box. The idea stems from a criterion of failure that Charles Darwin himself offered up regarding his theory of evolution. Here's what Darwin said. If it could be demonstrated that any complex organ existed which could not possibly have been formed by numerous, successive, slight modifications, my theory would absolutely break down.
Now, this admission of Charles Darwin's has been a key area for those critical of his theory to look carefully at and to try to target. Behe defined the term irreducibly complex as referring to, quote, a single system composed of several well matched interacting parts that contribute to the basic function wherein the removal of any one of the parts causes the system to effectively cease functioning.
And since natural selection can only choose systems that are already working, if a biological system cannot be produced gradually, it would have to arise as an integrated unit in one fell swoop for natural selection to have anything to act on. Behe also notes that as the complexity of an interacting system increases, the likelihood of natural selection producing it, not even through a direct process, but even an indirect, circuitous route would drop precipitously. And the more systems we can identify as irreducibly complex, the more we can say that Darwin's own criterion of failure has been met. Indeed, Richard Dawkins has said that if evolution is not gradual, it ceases to have any explanatory power at all. Now, Jonathan, would you say that a number of crucial components involved in sexual reproduction are irreducibly complex systems? And why did you come to that conclusion?
[00:12:56] Speaker A: Absolutely.
Various features and properties of the head, the middle piece, and the flagellum of the sperm cell, together with the properties of the seminal fluid, are critical to the ultimate objective of the sperm cell arriving at the egg and performing fertilization. So if any one of those components was missing or is not working as it ought to, then the sperm cell is rendered completely impotent and reproduction can't occur.
The phenomenon of reproduction points to a cause that possesses foresight, one that can visualize a fore ordained outcome and bring everything together that's needed to actualize that higher level purpose or end goal. And there's no cause in the universe that is known to have such a capacity of foresight other than conscious deliberation or intelligent design. And so that's why I am an intelligent design proponent.
[00:14:00] Speaker B: Right. Well, in evaluating whether a biological system is irreducibly complex, the key is whether a process like natural selection could evolve the system in a gradual manner, or, as Darwin put it, by numerous, successive, slight modifications. And we have to remember, as Behi points out, that there's a difference between physical precursors and conceptual precursors. We could say, for example, and he details this in his book Darwin's Black Box, that a bicycle is a simpler precursor to a motorcycle. It's a conceptual precursor. They look related and perform similar functions to one another. But darwinian evolution requires a physical precursor. And try as you might, a darwinian process of numerous, successive, slight modifications could never physically turn a bicycle into a motorcycle. It's a jump in function and complexity that is simply out of reach of a gradual blind process.
Jonathan, since science can't give us 100% proof, and we know this to be true. A likelihood ratio, however, can be determined upon examination of competing evidence. You and I have done an episode on bayesian reasoning and how it's helpful to an intelligent design understanding of the natural world. Can you just take a moment to tell us how bayesian reasoning might help us be more confident of irreducible complexity in biological systems?
[00:15:25] Speaker A: Sure. So the Bayesian approach to making the case for design would be as follows, that we observe certain features of the world, in particular living organisms, which are not particularly surprising. Supposing a mind is involved so irritably complex systems would be one such feature, given that well matched, interacting, well organized sets of parts that work together to achieve a higher level purpose are habitually associated in every other realm of experience with conscious activity. Because intelligent designers, or conscious agents, as I mentioned before, are uniquely able to visualize complex, higher level purposes and bring everything together needed to actualize or realize that end goal. And so, irritably complex systems are not particularly surprising if we suppose that a mind is involved. But they become wildly surprising, supposing that no mind is involved, that all we have to work with are naturalistic processes. Because when you require multiple codependent parts that have to be very carefully assembled and well matched one to the other, in order to perform a high level objective, how, by a blind, mindless process, are you going to be able to put that system together one step at a time, while retaining selective utility at every turn, it seems to strength, credibility. And so the more parts that are necessary or the more functions that are needed in order for this higher level purpose to be realized, the more improbable it is going to be, and the probabilities, or the improbabilities are going to multiply exponentially as each new function is, is needed. And so it's enormously improbable on the supposition that only naturalistic processes are involved. And there's no teleology underlying the origins of these systems, whereas it's not especially improbable if a mind was involved. And so, in light of that top heavy likelihood ratio, overwhelmingly top heavy likelihood ratio, it favors a design hypothesis, and given that chance, is such a big factor from a naturalistic perspective, in explaining each of these irritably complex systems, of which there are many thousands in biology, these are actually epistemically independent of each other. And so the Bayes factors, if you will, which is essentially the result of that ratio. So base factor of two, for example, means that the feature is twice as likely given one hypothesis versus another. The base factors multiply together because of their epistemic independence. And so you end up with this overwhelmingly top heavy likelihood ratio, particularly when you consider all of the many hundreds or thousands of irreducibly complex systems taken in aggregate.
[00:18:09] Speaker B: Yeah. And I would say, and listeners may agree, who have been studying this topic for a while, you can tell the problems for evolutionary theory to explain these irreducibly complex systems and the level of complexity in biological systems. You can tell that this is getting know year by year, decade by decade. And in fact, listeners, if you do study Mike Behe's books and his work, that's one of the main points he's making, is, look, we have a revolution in microbiology that is revealing layer upon layer upon layer of complexity that we didn't know about before. And when you throw in the irreducible complexity argument and the fact that darwinian evolution would struggle to come up with these systems all in one place before they can be selected for, it just really results in an insurmountable problem. Well, since B, he put forward his arguments for irreducible complexity over 25 years ago, a number of people have tried to refute him naturally. Jonathan, are you aware of some of the proposals that have been put forward both when his book first came out and maybe over the last 25 years, what have been done with those? Have they been challenged and refuted?
[00:19:23] Speaker A: Absolutely. So the most popular rejoinder to behave thesis has been the cooption or acceptation model, where you could borrow parts from another system and incorporate them into a new Ernest P. Complex system. So, for example, the type three secretion system is an injectosome or a needle, which injects toxins into multicellular organisms. It's found, for example, in Yourcinia pestis, which is a causative agent of bubonic plague. And the type three secretion system is itself a part of the bacterial flagellum. It's also used for the bacterial flagellum to export proteins during assembly. And so Ken Miller and Nick Matsky and Mark Palin and others put forward the type three secretion system as an evolutionary precursor of the bacterial flagellum. This has now turned out to be completely incorrect. There is a number of different lines of evidence that indicate that the type three secretion system is an evolutionary degradation product of the flagellum, rather than the reverse. The bacterial flagellum actually is much more widely distributed than the type three secretion system, which is much more taxonomically restricted. And so it suggests that the type three secretion system came later. It also makes sense from an evolutionary perspective, because there's a selection pressure to be able to swim long before there's a selection pressure to inject toxins into mult cellular organisms. There's also phylogenetic evidence that indicates that the type three secretion system came later. So, furthermore, you've also got the problem of assembling the bacterial flagellum. And so you have the arrangement of the genes along the bacterial chromosome that forms different operons, which are collections of genes that are under control of a common promoter and are expressed together that is non random, and actually that forms what we call a transcriptional hierarchy. So you have a very carefully controlled and choreographed assembly system for putting the bacterial flagellum together.
And then, of course, the parts have to be well matched, one to the other and so forth. So I don't buy the cooption scenario. Another approach to explaining irresistible complex, or to undermining the argument from irritable complexity is to point to examples in nature where a component that is necessary in one organism is not necessary in another organism and may in fact be absent from another organism.
But I don't find this rejoinder compelling either, for the reason that, as you mentioned in your preamble, behinguishes between a physical precursor and a conceptual precursor. Right? So, for example, a unicycle is a conceptual precursor to a bicycle. A unicycle is simpler than a bicycle. A unicycle only has one wheel, a bicycle has two wheels. But can you transform a unicycle into a bicycle just by adding another wheel? Well, no, it requires a lot more codependent changes for one to transform into the other. And there are examples that one could draw from biology to illustrate this point as well. I also think that it is important to nuance the argument from irredicible complexity in terms of. So the way that I see the concept of irredisible complexity is not in terms of the number of structural parts that need to be present, but rather the functions that need to be performed in order for this higher level function to be realized. And so, in principle, you could have one part that performs multiple of those functions, or you could have multiple proteins that are necessary for that one function, or contribute to that one function, and you might even have a level of redundancy there and so forth. But I think that in many of those cases where you see that there is a protein that's needed in one organism, but absent in another, it is generally the case that there's a different set of proteins that are performing the same function or that you have a different idea or a different solution to the same problem.
And so these rejoinder series for complexity have never carried a lot of sway with me.
[00:23:35] Speaker B: Right, well, and it's like behavior, come along. An eager, inventive person who wants to change sits down with a bicycle and just spends hours and hours fixing it up and making it into a motorcycle. That could happen, but we already know that minds can build irreducibly complex systems. What we're challenging here is a darwinian process, a blind, gradual process consisting of numerous, successive, slight modifications doing. No, no, we're not going to jump to that so quickly. Well, when we find irreversible complexity, then in a biological system, it becomes in behalf structural obstacle to thinking darwinian processes could do the job. And as you put it, Jonathan, in your article on seminal fluid and sperm capacitation recently, the phenomenon of human reproduction points to a cause with foresight, one that can visualize a foreordained outcome and bring together everything needed to realize that end goal. There is no cause in the universe that is known to have such a capacity of foresight other than intelligent design. Just wanted to reiterate that because those are strong words and I think very appropriate here. Well, that's all the time we have for this episode. In another podcast, we're going to look at more components of the irreducibly complex core needed for successful sexual reproduction, including the male reproductive functions, as well as perhaps egg cells in female reproductive function. These indeed are spicy problems for an evolutionary process to explain, but the design and complexity of these crucial components, not a surprise on a design hypothesis. Jonathan, thanks for your time today.
[00:25:18] Speaker A: Thank you. Great to be here.
[00:25:19] Speaker B: Well, we'll include Jonathan's articles in the show notes for this episode, which you'll
[email protected] and if you want more of Dr. McClatchy's work, just hop on to his website, jonathanmcclachey.com. And if you're wondering how to spell that scottish last name, it's mclatchie. Jonathanmcclachey.com. Well, that's it for id the future. I'm Andrew McDermott. Thanks for listening.
[00:25:48] Speaker A: Visit us at id and intelligentdesign.org. This program is copyright Discovery Institute and recorded by its center for Science and Culture.
