So Many Question Marks About Sex and Reproduction

Let us look at human sexual activity and human reproduction, and consider how little such things are understood by the modern biologist. The average male first becomes aware of sex when he finds rather suddenly around the age of puberty that he can get pleasure by rubbing his penis. We might think this part of sex is thoroughly understood by the modern biologist, although there are reasons for doubting that claim, since the origin of sexual organs is hard to explain (for reasons I'll discuss later in this post). But at least given the male anatomy, it is easy to understand why a male would engage in sexual self-stimulation, as such an act immediately produces pleasure. While it may seem that sexual attraction of a male to a female is also easy to understand, it is not so clear why that occurs.

Of course, if we think of a “final cause” type of reason why males should be sexually attracted to females, a reason involving end purposes, the reason is that such attraction helps to achieve reproduction which perpetuates the species. But there is no clear immediate cause for why a male should be sexually attracted so strongly to a female. From the standpoint of sheer physical pleasure, there is no obvious reason why a male should find it much more pleasurable to engage in sexual intercourse than to engage in masturbation.

There is no DNA explanation for why males should be attracted to females. Essentially DNA is an information system for storing the chemicals (amino acids) that make up proteins and similar molecules in the human body. There is no way that DNA could be expressing something like some “target of attraction” (such as a female form) that is passed on to males as a message to be attracted to some particular type of physical form. In some species the female emits a chemical or scent that causes arousal in the male, but that does not seem to occur to any major degree in humans.

There are other aspects of male sexual attraction that biologists have no good explanation for. Males are enormously interested in seeing unclothed females, but such an attraction has no obvious biological explanation. Women don't have to be naked to engage in sexual intercourse. No biological end is achieved when adult men are sexually attracted to naked female breasts. It is also puzzling that a man seems just as interested in engaging in oral sex with a female as vaginal sex. From a biological standpoint, this is hard to explain, given that oral sex achieves no reproductive end.

We can imagine a set of sexual behavior characteristics for males that would make the most sense from a biological, reproductive and evolutionary standpoint. They would be something like this:

1. Males would be very interested in having vaginal sex with females, but not at all interested in oral sex that has no reproduction value.
2. Males would be very interested in sex that achieves reproduction, but not interested in just looking at pictures or videos of other people having sex or looking at pictures or videos of naked women.
3. Males would have sex with as many women as they could over a lifetime to maximize their offspring, and would not commit to marriages restricting their sexual partners.
4. Males would be exclusively heterosexual.
5. Males would not be interested in any type of sex that involved birth control that prevented reproduction.
6. Males would have no interest in having sex with females older than 40 who are unlikely to become pregnant.

Actual male sexual behavior drastically departs from such a set of characteristics. In the USA a large fraction of all males spend more  time looking at pornography than they do engaging in any activity that might result in or lead to reproduction. The average single male seeks to have sex that does not result in reproduction, and is just as interested in oral sex as vaginal sex. Most men do commit to marriage that restricts their sexual partners. Very many men are sexually attracted to women over 40, and about 5% of the male population is homosexual.

It seems, then, that actual male sexual behavior is something very hard for a biologist to explain. What is particularly baffling from a biological explanation standpoint is homosexuality. Why should about five percent of the male population be not interested in having sex with females, but instead interested in having sex with males? The fact of widespread homosexuality defies the predictions of Darwinism, which predicts that organisms should have characteristics that maximize their reproduction.

The specific characteristics of human sexual behavior are hard-to-explain from a biological standpoint, and we can say the same thing about the part of human reproduction that occurs after the moment of conception. The fact is: none of us knows how babies originate. We merely know something a million times simpler: how women become pregnant. 

By saying “none of us knows how babies originate” what I mean is that no one knows how it is that a fertilized egg is able to progress to become a full-sized baby. In our society we have the speech custom of saying that when a child learns how a fertilized egg originates in a womb after sexual intercourse between a male and female, that child is said to have learned “where babies come from.” But what such a child has learned is how a female egg becomes fertilized, which is much different from how it is that a full-sized baby is able to originate in a womb.

Now, you may say, “I know where babies come from – it's more complicated than just sexual intercourse.” You may then tell me a story like the one below, which is often told in popular science literature.

"Babies are able to originate in the womb because the DNA blueprint of a human in read. Inside each person's DNA is a blueprint of a human body, a kind of recipe for making a human. So inside the womb what's going on is that the DNA blueprint or recipe is being read, and the baby appears in a form matching that blueprint."

But the idea that DNA is a blueprint or recipe for making a human is false. There are several reasons why it cannot be true. The first is that human DNA has been thoroughly analyzed in massive multi-year scientific projects such as the Human Genome Project and the ENCODE project, and no blueprint or recipe for making a human has been found in DNA. For example, there is no known place in DNA where it specifies that human males have one head or two legs or two arms or ten fingers or one penis or two eyes. The second reason is that the inherent expressive limitations of DNA means it could not possibly be stating a human blueprint or a recipe for making a human. Just as the physical limitations of an electric  traffic light restrict it to expressing only 3 commands (stop, walk, or proceed carefully), the physical limitations of DNA means that it is limited to expressing chemical information (such as the amino acids that make up a protein), and mean that DNA is not at all suitable for expressing three-dimensional body plans or some recipe for making three-dimensional structures. The third reason is that there is nothing in a human womb that would be capable of interpreting a human body plan if it were written in DNA.

Consider a construction blueprint, a big sheet of paper stating the plan for a structure to be built. It is never true that you can go to some uninhabited construction site with lots of bricks, nails, pipes and lumber, drop a blueprint in the middle of the site, and then expect a building to be built that matches the blueprint. For something to be constructed using a blueprint, there must be an intelligent blueprint reader smart enough to understand the complex instructions, and convert them into specific actions that result in the construction of the finished product. Blueprints don't build buildings; people build buildings using blueprints. It works the same for recipes. Recipes don't make food; humans make food after reading recipes.

Imagine if it were true that DNA stored a blueprint or recipe for making a human (and I have just given two reasons why this is not true). Even in such a case, we would not at all have an explanation for how a fertilized egg progresses to become a full-sized baby. For inside the female womb there would be nothing that we know of smart enough to read incredibly complex instructions such as a blueprint or recipe for making a human. Inside the womb there's no equivalent of a construction crew or a blueprint reader. A womb doesn't have a brain inside it smart enough to read a blueprint for making a human.

Moreover, the whole idea of a blueprint or recipe for making something as internally dynamic as a human is nonsensical. A blueprint is something that specifies the layout of a static building that doesn't move. A recipe is something for making some piece of food that doesn't move. But humans are enormously dynamic in several ways, including the growth of their bodies and the immensity of constant dynamic activity inside the body.  The activity of cells and organs is as complex as the busy activity within a huge defense plant or automobile factory.  You could never specify the enormous complexities of a human's internal biochemical dynamics through a static snapshot such as a blueprint. 

We therefore have four very good reasons for thinking that the “babies arise from the blueprints in DNA” idea is bunk. The first is that there is in DNA no blueprint or recipe for making a human or any of its organs or any of its cells.  DNA does not specify a body plan, and genotypes do not specify phenotypes (they merely influence phenotypes). The second reason is that given the inherent expressive limitations of DNA (which restrict it to chemistry), there is no way that DNA could be storing a blueprint or recipe for making a human. The third reason is that even if human DNA had a blueprint or recipe for making a human (which would be fantastically complex instructions), there would be nothing in a human womb capable of understanding such fantastically complicated instructions and executing them to cause a fertilized egg to progress to become a full-sized baby. The fourth is that a blueprint or recipe could only specify the state of a human organism at one instant, not the incredibly complicated tale of a human's internal dynamics or the developmental history of a human from a speck-sized egg to a full grown adult. 

So how is it that humans are able to reproduce? Nobody understands such a thing. We merely understand how a human egg can become fertilized, which is a vastly different thing from understanding human reproduction. We cannot say we understand human reproduction until we understand how it is that a fertilized egg is able to progress to become a full-sized baby, and no one has a credible explanation for how such a miracle of organization can occur.  Scientists don't even understand any low-level factors sufficient to explain the reproduction of a single cell, so how could they possibly understand the almost infinitely more complicated problem of the reproduction of a large visible organism built from fantastically complex arrangements of two hundred different types of cells? 

The lack of a prevailing theory of development (a theory explaining the progression from a newly fertilized egg to a full-sized baby) is confessed by the article on "Developmental biology" in the Stanford Encylopedia of Philosophy.  In that article we read the following:

"It is uncommon to find presentations of developmental biology that make reference to a theory of development. Instead, we find references to families of approaches (developmental genetics, experimental embryology, cell biology, and molecular biology) or catalogues of 'key molecular components' (transcription factor families, inducing factor families, cytoskeleton or cell adhesion molecules, and extracellular matrix components). No standard theory or group of models provides theoretical scaffolding in the major textbooks (e.g., Slack 2013; Wolpert et al. 2010; Gilbert 2010). The absence of any reference to a theory of development or some set of core explanatory models is prima facie puzzling. Why is it so difficult to identify a constitutive theory for developmental biology?"

The failure of attempts to explain morphogenesis in a bottom-up manner suggest the need for a novel top-down hypothesis about what causes a newly fertilized egg to progress to become a human -- the idea that every human being arises because of the action of some reality outside of a human being. Nature never told us that human beings arise because of "bottom-up" action of mere molecules. It was merely biologists who hastily assumed such a thing. 

There is another great mystery involving sex and reproduction: the origin of the human reproductive system. Scientists have no credible explanation for such a thing. The explanation that such a thing appeared because of natural selection (the supposed fact that fit things reproduce more) smells like circular reasoning. Since natural selection simply means the superior reproduction rate of a fitter organism, you cannot use such an idea to explain the origin of a reproduction system itself; for unless a reproduction system already exists, there can be no reproduction.

In the case of the human reproduction system, we have the “incipient stages” problem to the highest degree. The incipient stages problem is that natural selection typically cannot explain the earliest stages of a complex biological innovation, for such stages are almost always useless. What use would one tenth of a testicle be, or one tenth of a penis, or one tenth of a vaginal canal, or one tenth of a uterus? No use at all. Natural selection cannot explain the appearance of such things.

One of the gravest difficulties in explaining complex biological innovations is when you have a problem of interlocking dependencies, a kind of “which came first, the chicken or the egg” problem. We have that problem in the highest extent in trying to naturally explain the human reproduction system. For example, we may ask: which came first, the testicle or the ovary? We cannot imagine either appearing first because of natural selection, since both are useless without the other. The problem is not solved by imagining gradual changes from some earlier species with a different reproduction system, because the same type of “which came first, the chicken or the egg” problem will be found in that earlier species.

Scientists do not have a credible explanation for the origin of sexual reproduction in any organism. If a planet had only organisms engaging in asexual reproduction (like the fission reproduction that bacteria use), it would seem very probable that life on that planet would just continue to use such reproduction, without moving to sexual reproduction, which is vastly different. Asexual reproduction is actually a more efficient way for an organism to transmit its genes, so under Darwinian assumptions we would expect that a planet would just keep using asexual reproduction. 

When scientists try to offer explanations for how sexual reproduction appeared, they resort to "final cause" type explanations, that amount to kind of saying, "It happened because the end result was better." But they fail to provide a credible explanation of how nature could have moved from asexual reproduction to sexual reproduction, a transition that seems no more likely than a computer randomly switching its operating system from the Apple system to the Microsoft system.  

In imagining any such transitions, there is a gigantic general problem: what we can call the problem of nonfunctional intermediates. It is typically true that we cannot imagine a transition between two very different and highly-functional biological things without a passage through an intermediate state that is non-functional.  For example, if over very many thousands or millions of years one specialized protein molecule changed gradually to become some other specialized protein molecule, there would have been an intermediate non-functional state; but in such a state such a molecule would have tended to have fallen out of a gene pool, preventing the imagined transition. In a transition from asexual reproduction to sexual reproduction, such a problem of nonfunctional intermediates is particularly severe. For we cannot imagine any species passing through a nonfunctional intermediate state involving reproduction, one in which reproduction could not occur. As soon as such a state was reached, the species would become extinct. 

Let us consider an elementary example of nonfunctional intermediates during a transition from one functional thing to another. Suppose I have a red "stop" sign, and I wish to modify this to serve another function. I can do this in three steps:

(1) I paint over the "s" in "stop."
(2) I paint over the "p" in "stop" to make it "w."
(3) I then paint "zone" under what was originally the word "stop."

Now I have changed my functional "stop" sign to a functional sign saying "tow zone."  A transition has occurred from one functional state to another. But there was no way to do this without passing through a nonfunctional intermediate state.  The sign is functional when it says either "stop" or "tow zone." But the sign is nonfunctional as a traffic sign if it just said "top" or "tow" or "stopw" (as it would have after only step 1 or only step 2 or only steps 1 and 2 or only step 3).  If it is clear from this example that you cannot avoid passing through a nonfunctional intermediate when changing a very simple "stop" sign into a very simple "tow zone" sign, it should be far more clear that you could not avoid passing through a nonfunctional intermediate state when making a transition almost infinitely more complicated: a transition from asexual reproduction to sexual reproduction. 

We have in this essay a discussion of why sexual reproduction is baffling from the standpoint of evolutionary dogma.  The author (an orthodox Darwinist) states that " the payoffs of asexual baby-making are quite clear, while its male-and-female based alternative is loaded with liabilities."  These include the fact that with sexual reproduction, there's only a 50% chance of a favorable genetic trait being transmitted to an ancestor, as opposed to a 100% chance with asexual reproduction.  Eventually the author tries to argue not very convincingly that sexual reproduction might be superior in the very long term because "sex enables individuals to diversify their long-term bets." 

A similar approach has been taken by quite a few writers who try to suggest that ultimately in the very long run sexual reproduction might be superior. But as blind evolution lacks all foresight, there is no reason why it would ever make drastic coordinated changes in organisms because in the very long run (generations later) this might leave something superior.  Let us imagine a species that successfully reproduced asexually starting to gradually transform into a species that reproduced sexually. In the short term, this would be disadvantageous, surely leading to a decrease in reproductive success while the species was in some intermediate state in which asexual reproduction had been damaged, but sexual reproduction was not yet possible. So such a transformation would never occur under Darwinian assumptions. 

Darwinian evolution should always be as short-sighted as the law of gravity.  Gravity "wants things to fall," but gravity never causes a ball to roll up a mountain top so that it can have a bigger fall from a mountain top. Gravity doesn't have the foresight for such a thing. And similarly, since blind evolution should lack all foresight, we can imagine no plausible path by which an asexually reproducing species would ever transform into a sexually reproducing species. It is a fallacy to talk about some possible eventual superiority of sexually reproducing organisms, if you also maintain that a path leading to sexual reproduction (having negative short-term effects) was produced by a blind process in which immediate rewards are all that count.  So today's biologists lack any credible explanation for the origin of sexual reproduction. 

Overall it seems that the great majority of sex and reproduction is not well understood by biologists. You may start to realize how little we know about these topics when we consider that nowhere in DNA is there any such thing as a specification of the physical structure of either the male or female reproductive organs, nor is there any such thing in DNA as a specification of any of the cell types used by such organs. Since such things cannot be explained by "favorable DNA mutations" or any other changes in DNA, we can't even explain very well the things involved in the very beginning of reproduction.  A scientific web page states that "the complexity that we observe in cells can be compared to that of airplanes." The reproduction of a single eukaryotic cell is a marvel comparable to an airplane splitting into two full copies of itself, so that one airplane splits to become two functional airplanes as big as the first. We understand neither that little microscropic marvel nor the almost infinitely more impressive macroscopic marvel of a full-sized human growing from a tiny speck-like egg. 

Postscript: The recent Quanta magazine article "Why Sex? Biologists Find New Explanations" does nothing to change my previously stated opinion that biologists have no credible account for the origin of sex.  The discussion is purely advantage-oriented type of speculation, in which biologists speculate that sexual reproduction might be better for one reason or another. There is no coherent theory advanced as to how sexual reproduction could have naturally originated, or how life could have naturally made a transition from asexual reproduction to sexual reproduction.  In this regard the biologist is like someone claiming that a pumpkin and mice turned into a horse-drawn coach (as in the Cinderalla story), and who offer the "explanation" that this happened because the horse-drawn coach was nicer transportation.