The mouth that cannot bite
Warning: Today’s post has not been approved by the Family Research Council.
There’s a puzzle about evolution that’s been bothering me for years. The most vivid way to state it is as follows: why don’t vaginas have retractable teeth?
Think about it. If vaginas had teeth, rape would be difficult if not impossible. Females would have much greater control over which males could impregnate them. Wouldn’t a biting vagina be a useful Darwinian adaptation?
Of course, the question applies not only to humans, but to any species where the females can be impregnated against their will. (I guess seahorses and black widow spiders don’t count.)
I realize that feminists, psychoanalysts, and comedians could all have a field day with my puzzle, but let’s set that aside and see if we can actually answer it. I can think of five hypotheses, but none of them completely satisfy me.
The first is the boring “spandrels” hypothesis: that putting teeth in vaginas would be too difficult embryologically to be worth the Darwinian payoff. This hypothesis would only convince me if accompanied by an explanation of why a biting vagina would be so much harder to build than a bee stinger, or an elephant tusk, or any of evolution’s other strange inventions.
The second hypothesis is that, if vaginas had teeth, then rapists would just threaten their victims with injury or death if they resisted (as, alas, they often do anyway). But this hypothesis can be made irrelevant by changing the thought experiment a little. Instead of a biting vagina, imagine a flap between the vagina and uterus that could be open or closed at will. If a woman had such a flap, then she could consciously decide whether to let a sex partner impregnate her, without the partner knowing her decision until possibly months later. In other words, she would have built-in birth control.
The third hypothesis is that, even without the teeth or flap, women already have lots of control over which sex partners can impregnate them. As we all know, women in developed countries gained such control in the 20th century — and despite the best efforts of the Republicans, they’ve fortunately retained it, more or less, in every US state except South Dakota. But I’m asking whether women had such control for most of evolutionary history, and also whether females elsewhere in the animal kingdom have it.
In particular, you might have heard the controversial theory that a woman can “choose” to retain more of her partner’s sperm (thereby increasing the chance of conception) by having an orgasm — and indeed, that that’s why the female orgasm evolved in the first place. This theory, if true, would be one example of what I’m talking about, but not the only possible example. Do any of you know how far back in human history abortions were performed — and also, whether any non-human animals perform abortions?
The fourth hypothesis is what I’ll call “genetic paternalism.” This is the idea that, while giving birth to a rapist’s child is an unimaginable trauma from the woman’s perspective, her genes’ perspective might differ from hers. From the genes’ standpoint, maybe the child will grow up to become a rapist himself, thereby spreading his mother’s genes to yet more victims.
(Here I should state an obvious ground rule: when engaging in Darwinian speculation, you have to wear the distinction between “is” and “ought” like a radiation suit. There’s no scientific discovery that could possibly justify violence against women, since the wrongness of such violence isn’t based on science to begin with.)
Of course, the genetic paternalism hypothesis begs the question of why a woman’s genes would build a brain so opposed to the genes’ own interests. But that question shows up all over the place in human evolution.
The fifth hypothesis is that vaginas lack teeth for the same reason many women wear high heels and the Chinese used to mutilate girls’ feet. As Carl Sagan and Ann Druyan point out in their superb book Shadows of Forgotten Ancestors, men have always fetishized female helplessness. For most of human history, marriage wasn’t a union of soulmates; it was a deal between the groom and the bride’s parents. If a man “invested” in a wife, he’d want to be sure she would bear him children, just like if he invested in a cow, he’d want to be sure it would give him milk. (In Fiddler on the Roof, there’s a hilarious exchange between Tevye the dairyman and Lazar Wolf the butcher playing on that similarity.) So, if most women had teeth in their vaginas, then a woman who was known not to have such teeth might be a hot commodity on the marriage market. Of course, that leaves open the question of how she would advertise her toothlessness to prospective suitors (“Hi, I’m Alice, and my vagina doesn’t bite!”).
Surprisingly, I’ve never seen my “biting vagina puzzle” discussed in any book or article on evolutionary biology. (I’d be grateful for a reference.) I have seen plenty of other sex-related puzzles. For example, why are there homosexuals? Why don’t women just clone themselves, instead of “diluting” their genetic contribution by 50% by mixing their genes with a man’s? For that matter, why is there sex in the first place? To me, all these questions are so perplexing that it’s a wonder the creationists never harp on them. I guess that to harp on them, they’d first have to understand them.
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Comment #1 March 24th, 2006 at 9:02 am
Speaking of South Dakota–
The Oglala Sioux Tribe on the Pine Ridge Reservation has pledged to open a Planned Parenthood clinic on reservation land. No problem, since state law doesn’t apply there.
This would be great, huh? To put your money down,
ATTN: PRESIDENT FIRE THUNDER
PO BOX 990
Martin, SD 57751
(Full Story)
Comment #2 March 24th, 2006 at 9:06 am
Interesting post.
I think its worth mentioning, that the question in your fifth hypothesis does not really arise (in my opinion) since women would probably not be born with teeths in their vagina since the start of evolution of mankind. Those teeth would have to evolve during this evolution. Therefore it is rather the case, that the first woman born with such teeth would be rejected by any man than that any woman had to communicate her teethlessness for being more attractive.
Comment #3 March 24th, 2006 at 9:11 am
It is a good puzzle, and one that I’ve pondered before. I didn’t come up with any more than you did however.
Comment #4 March 24th, 2006 at 9:14 am
Scott, I think that one reason that the retractable teeth you mention don’t pop up in the literature too frequently is that they don’t really increase fitness (the biological kind). While the teeth clearly allow a female to be more selective in chosing a mate, they don’t necesarily increase the females’s ability to mate and rear offspring capable of mating. Evolution is environment specific however, so perhaps you could argue that in a world rife with STD’s, women with these teeth are better able to shield their offspring against harmful birth defects, providing them with a reproductive advantage that can be selected for?
Comment #5 March 24th, 2006 at 9:29 am
For most of human history, marriage wasn’t a union of soulmates; it was a deal between the groom and the bride’s parents. If a man “invested” in a wife, he’d want to be sure she would bear him children, just like if he invested in a cow, he’d want to be sure it would give him milk.
You’ve actually hit on the reason why rates of premarital sex were so high in 18th century America (not all of the founding fathers were puritans 🙂 ). In agrarian societies (my guess is that this is still true today in some places), children are often needed as workers, putting an infertile couple at a severe disadvantage. The practice of having a child before marriage naturally arose as a way to ensure that the wife was capable of having chidlren.
Comment #6 March 24th, 2006 at 10:05 am
Scott,
is this post in preparation for the upcoming 150th birthday of Sigmund F. 8-?
Comment #7 March 24th, 2006 at 10:19 am
Darwinian Natural Selection requires that the trait exists in the genotype.
Mutation, Epigenetics or HGT/LGT offer alternative explanations for the existence of the trait (or more properly an origination event).
I have a difficult time understanding how, given lockjaw and temporo-mandibular joint (or the pelvic? derivative) how any propagation could occur with any durability in the population.
Given that you are a single compsci male, do you know for certain that this condition does not exist? Do you have any tips for identification of this condition (or absence of condition)? Other single compsci males now have another reason to avoid dating in the absence of any authoritative data on this topic. This leads to further crisis.
But just in case, my neighbor teaches at the School of Dentistry. I’ll ask him for tips on proper hygiene. I haven’t seen any hygiene products, but I suppose, toothpaste is for general cleaning regardless of site.
http://en.wikipedia.org/wiki/Vagina_dentata
Comment #8 March 24th, 2006 at 11:44 am
I imagine that, in a society where rapes that impregnated the victim had severe reproductive consequences (honor killings?) but other rapes didn’t, there would be some evolutionary pressure for the development of rape-infertility mechanisms.
But I’m not convinced that reasoning like “it would be a more pleasant society if this sort of situation were non-existent” has much to do with actual evolutionary pressure.
Comment #9 March 24th, 2006 at 12:16 pm
ok so I am a bit perplexed!
Reasoning along the lines of the question you raise — wouldn’t it then be a natural question why human skins haven’t hardened over the years to avoid damage by weapons.
I assume the natural progression over the years would be blunt damage -> spears -> swords -> bullets -> cluster bombs ….
Admittedly if a skin is calloused due to regular friction it becomes hard but still doesn’t exactly become bullet proof. On the other hand some animals definitely have such defense mechanisms.
So am I to assume that humans just dont get slaughtered enough to warrant those defense mechanisms ?
If we try to argue that we have developed better mechanisms to avoid such inflcition then couldn’t the same be argued for rape victims?
Jibran
Comment #10 March 24th, 2006 at 12:49 pm
So am I to assume that humans just dont get slaughtered enough to warrant those defense mechanisms?
Jibran, remember that it isn’t a case of being slaughtered enough to warrant the defense mechanisms that you mention so much as their ability to arise naturally as genetic mutations.
I don’t know whether you’ve been following the whole evolution vs creationsim (aka intelligent design) debate or not, but an example that often comes up is the process by which compex organs/tissues/biological mechanisms arise (of which hardened skin would be one). The concesus among scientists (the evolution supporters) is that these mechanisms normally originate in order to fulfill a different need entirely (the classic example is the eyeball originating not to provide sight per se but to provide sensitivity to light –look at a mole for instance).
While I haven’t really thought about it for too long, it seems unlikely to me that something as compelx as hardened skin would arise as the result of a single point mutation. On the other hand, it is possible that a mutation could cause some sort of skin condition (which increases fitness in a different way) that would serve as a precursor to your hardened skin; any ideas???
Comment #11 March 24th, 2006 at 1:18 pm
So how about this? Women did not need teeth. Let us see how it works in the animal realm, say among monkeys or lions. The only male in some social group, who can copulate with a woman is the alpha male. Because the alpha male is the strongest male (or rather the male who is best adapted to the environment) he was able to drive away all the other competitors. But since this guy is the strongest he also has the best genes, and the woman actually *wants* to have a lot of off-spring from him, because then her children will also carry his good genes. So she does not need teeth to protect herself from bad genes, her alpha male will do it for her.
Comment #12 March 24th, 2006 at 1:25 pm
If I remember correctly, some of the related questions are addressed in the book “How the Mind Works” by Steven Pinker.
Comment #13 March 24th, 2006 at 1:29 pm
There are a huge number of hypotheses.
The energy it takes to grow something could be used for other purposes, so efficiency must play a role as well.
More hypotheses:
1) The tiny increase in female control over mate selection they would give is not warranted by the amount of energy they would take to grow and maintain.
2) Mate selection can be accomplished about as well by other, more energy-efficient, means.
3) In the evolution of sexually reproducing organisms, there was never any state that could lead to it.
4) All intermediate states between “vagina without teeth” and “vagina with teeth” are less energy-efficient than “vagina without teeth” and give no additional reproductive benefit.
Comment #14 March 24th, 2006 at 1:30 pm
Scott. This post is what the internet was missing. Yes. Biting vaginas. Now we can all turn off our computers and go outside. Our work here is done.
Comment #15 March 24th, 2006 at 1:33 pm
http://consumating.com/photos/11277/large/38997.jpg
Comment #16 March 24th, 2006 at 3:03 pm
I think its worth mentioning, that the question in your fifth hypothesis does not really arise (in my opinion) since women would probably not be born with teeths in their vagina since the start of evolution of mankind. Those teeth would have to evolve during this evolution.
Anonymous 9:06: What if the apes who were the ancestors of humans also had teeth in their vaginas? In general, any explanation of the form “we don’t see trait X, since if a single mutant arose with X it wouldn’t survive” can only be partly convincing to me. What I really want is explanation of the form “even if everyone had trait X, the situation wouldn’t be stable against invasion.”
Comment #17 March 24th, 2006 at 3:08 pm
Scott, I think that one reason that the retractable teeth you mention don’t pop up in the literature too frequently is that they don’t really increase fitness (the biological kind). While the teeth clearly allow a female to be more selective in chosing a mate, they don’t necesarily increase the females’s ability to mate and rear offspring capable of mating.
Huh?? Being selective in choosing a mate DOES increase biological fitness. Why else would females throughout the animal kingdom be so picky?
Comment #18 March 24th, 2006 at 3:10 pm
is this post in preparation for the upcoming 150th birthday of Sigmund F. 8-?
That old charlatan? He doesn’t deserve the honor.
Comment #19 March 24th, 2006 at 3:19 pm
I imagine that, in a society where rapes that impregnated the victim had severe reproductive consequences (honor killings?) but other rapes didn’t, there would be some evolutionary pressure for the development of rape-infertility mechanisms.
But I’m not convinced that reasoning like “it would be a more pleasant society if this sort of situation were non-existent” has much to do with actual evolutionary pressure.
David: Such reasoning has nothing to do with actual evolutionary pressure.
But I don’t think you’re giving your hypothesis enough credit. Being spared from honor killing is good for the individual woman, not only for the society in which she lives!
Comment #20 March 24th, 2006 at 3:28 pm
ok so I am a bit perplexed!
Reasoning along the lines of the question you raise — wouldn’t it then be a natural question why human skins haven’t hardened over the years to avoid damage by weapons.
Jibran: Excellent question! The animals that do have hard exteriors are all sort of slow and cumbersome — think of armadillos, turtles, etc. At the very least, these animals seem to pay a high price in weight and flexibility. I’m not convinced that vaginal teeth would have anything like that evolutionary cost.
Comment #21 March 24th, 2006 at 3:45 pm
Given that you are a single compsci male, do you know for certain that this condition does not exist?
Your presupposition is wrong: I’m seeing a beautiful, easygoing yet highly intelligent girl named Kelly, who’s a CS grad student to a boot. But no, I don’t know for certain that the condition doesn’t exist. All I know is that, if all women suffer(?) from it, then at least one of them does a very consistent job of concealing it.
(Furthermore, there exists a sheep in New Zealand that is black on at least one side… 🙂 )
Comment #22 March 24th, 2006 at 4:13 pm
Huh?? Being selective in choosing a mate DOES increase biological fitness. Why else would females throughout the animal kingdom be so picky?
That a female is selective in itself does not change her or her offspring’s biological fitness. What increases (or decreases) the biological fitness of her offspring will be the genetic contribution of her mate. The reason that females throughout the animal kingdom are so picky is that they are competing to mate with a male that will increase the fitness of her offspring. For example, a woman might decide that she wants to mate with a male who is intelligent, hoping to pass on this trait to her chidlren (though in reality I’ve found that this is not always the case, sigh). Her decision to mate with an intelligent male is not what give her children increased fitness, it’s the intelligent male that will increase the offspring’s fitness.
In mathspeak, what I’m saying is that the relationship we’re talking about isn’t transitive:
Selectivity–>High fitness mate–>High fitness offspring
does not imply that:
Selectivity–>High fitness offspring.
Comment #23 March 24th, 2006 at 4:27 pm
Her decision to mate with an intelligent male is not what give her children increased fitness, it’s the intelligent male that will increase the offspring’s fitness.
That’s a pretty pedantic distinction — like saying that it’s not eating a fish per se that’s useful to a shark, only the actual digestion and metabolism of the fish.
Incidentally, in species with high male parental investment, the female might also be choosing a male who she thinks will be a good provider.
Comment #24 March 24th, 2006 at 4:45 pm
That’s a pretty pedantic distinction — like saying that it’s not eating a fish per se that’s useful to a shark, only the actual digestion and metabolism of the fish.
I think that it’s more like saying that “Bob is a drunk because he always goes to bars” rather than “Bob is a drunk because he’s always drinking beer.” After all, if Bob decided to stop going to bars and opted to stay home and drink, he’d still be a drunk. It wasn’t his decision to go to bars that made him a drunk, it was his drinking.
That some females choose to mate with a male that will be a good provider is obviously true. But do you think that this is a heritable trait rather than learned behavior?
Comment #25 March 24th, 2006 at 4:46 pm
I think the question is ill-posed. The theory of evolution is designed to explain what did happen (more so since randomness plays such a large role). It is unclear what would be a satisfactory explanation of something that didn’t happen…
I notice that all the sex-related puzzles you cite are of the “why?” category rather than the “why not?”.
I guess you’d just respond that this is a cop-out 🙂
Comment #26 March 24th, 2006 at 4:59 pm
cheshire cat:
I guess you’d just respond that this is a cop-out 🙂
That’s exactly what it is. The moment you tell yourself something is one way rather than another way “just because,” instead of trying to explain it in terms of something deeper, is the moment you’ve stopped doing science.
Comment #27 March 24th, 2006 at 5:14 pm
One more thing, cheshire cat:
It is unclear what would be a satisfactory explanation of something that didn’t happen…
I’m not asking why no vaginas ever had teeth, only why they don’t have teeth today. One satisfactory explanation for why something doesn’t exist is that, if it did exist, then it would quickly be wiped out. For example, that’s an accurate explanation for why we don’t see antimatter, stacks of hundred-dollar bills lying in the street, or animals that offer themselves to be eaten.
In the spirit of “why not,” I hereby offer three more questions, all of which are perfectly kosher for a Darwinian to ask:
Why haven’t any animals evolved built-in wheels?
Why don’t we have an extra eye on the back of our heads?
Why isn’t there any species with three sexes instead of two?
Comment #28 March 24th, 2006 at 5:37 pm
>while giving birth to a
> rapist’s child is an unimaginable
> trauma from the woman’s
> perspective, her genes’
> perspective might differ from
> hers.
I vote for that.
The genes don’t bother if someone decided to became a nun. Or is with depression. Or with any kind of issue that made her lost interest on sex. So they “prefer” to let their host (the female) be raped, that’s better than nothing.
But my use of “prefer” here is too anthropomorphized. Let me rephrase that this way: Females with excessive conscious control of their reproductive system tend to let less descendants than the the ones. So… today we see only the other ones.
In a nutshell: Genes create an individual to select partners, not to reject all of them.
Comment #29 March 24th, 2006 at 5:43 pm
Yes, but it seems to me to that that is the only kind of explanation that you find satisfactory. One could imagine a phenomenon which, once it originated, would with high probability be perpetuated. But we observe that the phenomenon does not exist at present. So what kind of explanation can we give? Merely that it hasn’t happened yet. Not much of an explanation, but…
You come up with some pretty clever explanations yourself, but your criteria for “satisfactoriness” are very unclear. And you could always justify being unsatisfied because this is a thought experiment in the first place. Now if it were a biologist saying that he was unsatisfied, one might trust his intuitions…
You’re a fan of Popper, aren’t you? I doubt he’d approve.
Comment #30 March 24th, 2006 at 5:44 pm
>Why don’t women just clone themselves,
>instead of “diluting” their genetic contribution
>by 50% by mixing their genes with a man’s?
>For that matter, why is there sex in the first place?
Are you actually asking that or just wondering why didn’t creatinists don’t ask it?
http://en.wikipedia.org/wiki/Sexual_reproduction
Comment #31 March 24th, 2006 at 5:55 pm
I think you have the question backwards. Human females go out of their way (their reproductive systems do) to avoid ruling out pregnancy. Any voluntary means of avoiding pregnancy would defeat a mechanism that presumably evolved for a reason.
Preventing impregnation would hardly require teeth. They could just abort any unwanted embryos, or not ovulate at all. That’s what other mammals do.
Most mammals only ovulate when they are ready to become pregnant, and when they do, they advertise the fact.
A Human doesn’t. She hides her state of fertility so well that she does not know herself. It isn’t that she can become pregnant at any time, she can’t. It’s that there is no way for the male, or any one else, to tell if she can.
I have seen discussions of this before. An obvious explanation is that it makes it easier to hide the paternaty of offspring.
In many mammals, new males systematically kill their mate’s existing infants. Even a slight possibility that they were his would protect them.
In the context of rape, the possibility of pregnancy might also give the male a reason not to harm the female. This does not work so well as an explanation, since rapists often severely injure or kill their victms.
If rape were motivated by reproduction, that would not happen.
Comment #32 March 24th, 2006 at 5:56 pm
Now if it were a biologist saying that he was unsatisfied, one might trust his intuitions…
You’re a fan of Popper, aren’t you? I doubt he’d approve.
If you’re a fan of Popper, you should realize that these arguments from authority aren’t going to carry much weight. 🙂
Look, it might be the case that something doesn’t exist, and that there’s no deep explanation for why it doesn’t exist. If so, that’s a pity, but there’s nothing to be done about it. What I object to is passing off “it just hasn’t happened yet” as a satisfying explanation, and using that as an excuse not to search for a better one. You might not find a real explanation, but you at least have to look.
Comment #33 March 24th, 2006 at 5:58 pm
>Why don’t women just clone themselves,
>instead of “diluting” their genetic contribution
>by 50% by mixing their genes with a man’s?
>For that matter, why is there sex in the first place?
Are you actually asking that or just wondering why didn’t creatinists don’t ask it?
I’m actually asking it. Clearly we have to reproduce, but why don’t we do so asexually?
Comment #34 March 24th, 2006 at 6:06 pm
Science is just as much about choosing questions as providing answers. I didn’t claim that “It hasn’t happened yet” is a satisfactory explanation, far from it. Merely that if we aren’t able to tell what a satisfactory explanation is, then we might be better off thinking abou tother things…
Comment #35 March 24th, 2006 at 6:10 pm
Oh, well, because with cloning variety will arise only with ocasional mutations. Imagine a sheep herd made only of Dolly clones. One plage could kill them all easisly. The more they are genetically different, the more resistant the population.
And sexual reprodution bring this variety, even without mutations. “Sex… is good to DNA”. (I heard this sentence in a Brazilian soap ppera, but I don’t know if the chacter was quoting someone.)
So… Why isn’t there any species with three sexes instead of two? I don’t know, why isn’t there any computers with ternary instead of binary?
Comment #36 March 24th, 2006 at 6:16 pm
I didn’t claim that “It hasn’t happened yet” is a satisfactory explanation, far from it. Merely that if we aren’t able to tell what a satisfactory explanation is, then we might be better off thinking abou tother things…
Are “Why don’t we see any magnetic monopoles?” and “Why don’t we see a fourth generation of quarks?” also questions that are best not thought about?
I will concede that you’re entitled to whatever scientific questions you like. Personally, I find the topic of biting vaginas to be fascinating.
Comment #37 March 24th, 2006 at 6:20 pm
>Why haven’t any animals evolved built-in wheels?
I always thought that was because wheels are detachable. How do you link the wheels with a blood vessel, for instance? It apply to plants too.
>Why don’t we have an extra eye on the back of our heads?
[self help mode on]
It’s to we only being able to look forward on our lives!
[self help mode off]
Comment #38 March 24th, 2006 at 6:22 pm
So… Why isn’t there any species with three sexes instead of two? I don’t know, why isn’t there any computers with ternary instead of binary?
A better analogy might be: why do mathematicians rarely bother to define algebras with ternary operations in addition to binary ones?
Answer: Because ternary operations can be built up from binary ones.
Similarly, a three-way combination of genes can be built up by composing two-way combinations.
I don’t know if that’s the right answer, but it’s at least a candidate.
Comment #39 March 24th, 2006 at 6:26 pm
>Why haven’t any animals evolved >built-in wheels?
I always thought that was because wheels are detachable. How do you link the wheels with a blood vessel, for instance? It apply to plants too.
Yes, that is an explanation I’ve seen, and a pretty convincing one. Another explanation is that there weren’t many paved roads 100 million years ago.
Comment #40 March 24th, 2006 at 6:28 pm
I was guessing you could say somethig like that, “3 cromossomes DNA can be polynomially reduced to 2 cromossomes DNA”… 🙂
I also think homossexuality could be such a mess… today we have straigh men and women, gay men and lesbians… With sexes A B and C we could have A atracted to B, A atracted to C, bi-sexual A attracted to B and C, tri-sexual A… well, you are familiar with exponentials.
Comment #41 March 24th, 2006 at 6:30 pm
Oh, well, because with cloning variety will arise only with ocasional mutations. Imagine a sheep herd made only of Dolly clones. One plage could kill them all easisly. The more they are genetically different, the more resistant the population.
Osias: Yes, I think that’s a large part of the explanation for why sex exists. But it still has to overcome the hurdle of explaining why some species (even some complex multicellular ones) manage to get by with asexual reproduction.
Comment #42 March 24th, 2006 at 6:32 pm
BTW, did you read the book http://en.wikipedia.org/wiki/The_Selfish_Gene ?
Comment #43 March 24th, 2006 at 6:35 pm
I also think homossexuality could be such a mess… today we have straigh men and women, gay men and lesbians… With sexes A B and C we could have A atracted to B, A atracted to C, bi-sexual A attracted to B and C, tri-sexual A… well, you are familiar with exponentials.
You should read The Gods Themselves by Isaac Asimov, particularly the middle third. It’s about beings in a different universe with three sexes, and is often considered the best thing Asimov ever wrote (which is very high praise).
Comment #44 March 24th, 2006 at 6:36 pm
BTW, did you read the book http://en.wikipedia.org/wiki/The_Selfish_Gene ?
I’ve read pretty much everything by Dawkins.
Comment #45 March 24th, 2006 at 6:44 pm
>why some species (even some
>complex multicellular ones)
>manage to get by with asexual
>reproduction.
Yes they “get by”. But the sexed ones, beyonde more resistant, evolve (adapt) faster. Do you remember the example of birds on Galapagos and beak size? It turns out that females prefer to mate with males with the largest beaks.
http://www.tierramerica.org/english/2005/1119/iarticulo.shtml
Comment #46 March 24th, 2006 at 7:10 pm
>why some species (even some
>complex multicellular ones)
>manage to get by with asexual
>reproduction.
Yes they “get by”. But the sexed ones, beyonde more resistant, evolve (adapt) faster. Do you remember the example of birds on Galapagos and beak size? It turns out that females prefer to mate with males with the largest beaks.
It actually depends on the environment (no suprise here) the population inhabits. In general, in environments where exploiting a niche is key to survival, sexual reproduction reigns (like osias said, they can evolve faster). On the other hand, asexual populations tend to be more common in environments where only the rate of reproduction is important to survival (they reproduce faster).
Comment #47 March 24th, 2006 at 7:11 pm
Ah, now we have it, you’re fascinated by the question . You like to obsess about the question. You really wouldn’t want an answer, because that would destroy the question 🙂
I doubt that fetishizing questions is science, on the other hand, I suppose good scientists do tend to fetishize questions…
Comment #48 March 24th, 2006 at 10:46 pm
it is a real puzzle – such retractable teeth there would be also helpful in climbing trees
Comment #49 March 24th, 2006 at 11:44 pm
Hey Scott –
You said, “There’s no scientific discovery that could possibly justify violence against women, since the wrongness of such violence isn’t based on science to begin with.)”
. . and while I agree with the ethical conclusion reached, I’m not sure you’re right in assuming there’s no Darwinian basis for an ethical system that prohibits sexual violence. Assuming that social cooperation is one of the human animal’s primary survival strategies, then anything that undermines the ability of people to live in society is detrimental to our survival.
And vaginas don’t have teeth because they’d somewhat complicate the process of giving birth.
(I’m not touching the South Dakota issue.)
Comment #50 March 25th, 2006 at 12:29 am
Hi Sonya,
Assuming that social cooperation is one of the human animal’s primary survival strategies, then anything that undermines the ability of people to live in society is detrimental to our survival.
Picture Genghis Khan riding through the Mongolian countryside, killing all the men in sight and raping their wives and daughters. Sure, what he’s doing is detrimental for other’s people genes — but all that matters in Darwinian terms is that it’s beneficial for his own genes. (Today, something like 5% of Asian men are descended from Genghis on the male line.)
In other words: Darwinism is not a theory of group survival; it’s a theory of individual gene survival.
Do you consider Genghis a paragon of virtue? If not, then I don’t think you can base morality on Darwinism.
And vaginas don’t have teeth because they’d somewhat complicate the process of giving birth.
That’s a novel theory! But it still doesn’t deal with retractable teeth.
Comment #51 March 25th, 2006 at 1:40 am
Since your example doesn’t particularly single out humans as any different from other mammals, the question is why mammals in general don’t have female defenses against pregnancy.
Since females could defend themselves just as well with claws or teeth in the usual places as in their vaginas, the real question is why females don’t have the capacity to simply decide not to get pregnant from a particular intercourse.
Part of the answer is that they sort of do – a female is significantly less likely to get pregnant from mating which she wasn’t very interested in, although I can’t tell you how dramatic this effect is off the top of my head, and it undoubtedly varies from species to species and situation to situation.
Another possible explanation is simply that throwing out perfectly good sperm is wasteful. Putting off pregnancy decreases total expected number of children, and that can in turn reduce the propogation of one’s DNA, so a female body has to have a very compelling reason to not get pregnant when the opportunity arises.
Comment #52 March 25th, 2006 at 1:58 am
Hi Bram,
Part of the answer is that they sort of do – a female is significantly less likely to get pregnant from mating which she wasn’t very interested in, although I can’t tell you how dramatic this effect is off the top of my head, and it undoubtedly varies from species to species and situation to situation.
Yeah, that was the third hypothesis in the post.
Another possible explanation is simply that throwing out perfectly good sperm is wasteful. Putting off pregnancy decreases total expected number of children, and that can in turn reduce the propogation of one’s DNA, so a female body has to have a very compelling reason to not get pregnant when the opportunity arises.
This answer just evades the question! If we were building a fitness-maximizing female, then of course we’d want her to get pregnant as often as possible. But, subject to that constraint, why shouldn’t we give her more choice rather than less over which males can impregnate her?
Comment #53 March 25th, 2006 at 4:42 am
As to the possibility of evolving animals with wheels, Richard Dawkins devotes a chapter to them in The Ancestor’s Tale. The truly wonderful fantasy epic His Dark Materials by Phillip Pullman actually has “animals with wheels” (in a different universe, of course), complete with an environment that naturally includes something like “paved roads” so as to facilitate their evolution in the first place. Both books (one fiction, one non-fiction) I highly recommend.
Comment #54 March 25th, 2006 at 10:54 am
As to the question of the history of abortion: I think it is older than history. Certainly it is in the Hippocratic oath. Prohibitions against it and euthanasia are the main content of that oath. The vast majority of it is about how doctors form a guild, they have to help each other and keep others out. The modern version only differs by deleting abortion, euthanasia, and Apollo.
Comment #55 March 25th, 2006 at 1:03 pm
Really it’s a question of how general and useful the technique is. While vaginal teeth would guard against some rapes, ther are other ways such as date rapes, incest, etc. that could still impregnate a woman. It’s just not an efficient technique.
Far more useful in this day and age would be the ability to internally induce an abortion at will.
Comment #56 March 25th, 2006 at 4:26 pm
Why isn’t there any species with three sexes instead of two?
Slime moulds have something like a dozen sexes. Probably there is also some species with exactly three sexes…
Comment #57 March 25th, 2006 at 5:18 pm
This is a hilariously funny thread. Some thoughts (and apologies for duplicating some previously mentioned ideas… too many comments to read them all!):
Q. Why haven’t organisms evolved wheels?
A. They have. The flagellum is actually driven by a little motor, which contains a wheel. On the other hand, wheels for locomotion (like with cars) are only useful on flat surfaces and such surfaces are rather rare in the natural world, so there would be little selective pressure to evolving them, i.e., animals with wheels would get wiped out through competition via pedal animals that can maneuver on uneven terrain more easily.
Q. Why don’t vaginas have teeth?
A. I suspect that no answer will ultimately satisfy the questioner, but let me add a piece to the puzzle. Note that vaginas are actually dual-purpose organs. Sperm goes in, baby comes out. Any change in one of those functions can’t interfere too much with the other. So, if vaginas has some selective mechanism to allow direct female choice over impregnation, the mechanism would have to also handle the dilation that occurs during birth. Teeth, which suggest a jaw-like mechanism, would be problematic because of the machinery necessary to unhinge that jaw to allow a baby to pass through. Now, some species actually do have something for direct selection. I forget its exact name, but the females actually store the sperm of their mates and, after some period of time to let the weak ones die out or something, they use this reservoir to impregnate themselves. I suspect that on the evolutionary landscape, such a strategy is more easily evolved from the basic and ubiquitous current vaginal machinery than teeth. And yes, the ease of evolving a solution does impact its likely development under whatever selective pressure. Ultimately, the answer should be something like this: over the course of evolution of the vaginal machinery, there was insufficient selective pressure to promote the particular strategy of flaps or teeth as the method of impregnation selection relative to (this is the important bit) alternative selective strategies and the fitness advantage those conferred. If you find that answer unsatisfying, then, as I recommend against trying a mid-career switch to evolutionary biology 🙂
Q. Why no eye in the back of our heads?
A. My money is on the argument that the evolutionary advantage of having such an eye is marginal since we have the ability to, through turning our heads, view about 270 degrees, and through turning our torso, view all 360. So, basically, the evolutionary path of evolving a rotational solution to the problem of seeing behind you was probably just more probable than the one of retaining some rigidity, but having a third eye. There are some species that went with multiple-eyes though – the one that comes to mind is a particular jellyfish that has four eye-clusters at each of its corners. I think the idea is that it needs to be able to see its prey quickly (little fish swim fast!) so that it can hunt well. It’s also, I believe, the only known jellyfish that actually hunts. Most jellyfish are basically blind.
Q. Why not some species with three sexes instead of two?
A. The three-body problem is significantly harder to solve than the two-body problem. So, the time required to find two other mates probably makes it evolutionarily untenable as compared to two-sex species. In other words, two-sex species just reproduce faster and spend less energy doing it. But, there are some species that do this. Slime mold is the most well-known, although that’s for different reasons.
Q. Why sexual recombination at all?
A. This is a deeper question, but my understanding is that recombination allows for bigger, directed jumps in fitness space. Let’s imagine that the fitness landscape is at least partially linearly seperable. Then, there are clear advantages of a search strategy that combines pieces of two good solutions over a search strategy that takes a single solution and mutates it slowly over time. (Actually, one could probably also argue that combining pieces of three solutions isn’t that much better (i.e., better enough) than two, which is why you don’t see three-sex species.) That is, the recombinant strategy can find better solutions, and faster, through selection as compared to simple mutation strategy. There certainly are species that reproduce through cloning, but they’re not under much selective pressure, so it doesn’t hurt them. On the other hand, if they were, sexual recombination would allow them to find better solutions in fewer generations, so it would probably evolve.
Comment #58 March 25th, 2006 at 5:24 pm
Anonymous 1:03:54 pm said…
Far more useful in this day and age would be the ability to internally induce an abortion at will.
A high percentage of miscarriages are the result of this kind of internal abortion. That is, the developing fetus and/or the mother’s body aborts the pregnancy if there are too many defects in the genetic material of the offspring.
For humans, and from the evolutionary perspective, it’s easier to legalize abortion than it is to bother with things on an evolutionary time-scale. Basically, there are sufficient alternative mechanisms for disposing of unwanted pregnancies that makes the evolution of something novel, under the current selective pressure regime, unlikely.
Comment #59 March 25th, 2006 at 5:42 pm
Scott said…
If we were building a fitness-maximizing female, then of course we’d want her to get pregnant as often as possible.
Actually, this is not always true. What it means to be a fitness-maximizing female depends on the current set of selective pressures. That is, the fitness landscape changes over time, so what is good in one epoch may not be good in the next. In humans and other large mammals, the strategy has developed that we invest a great deal of energy in our living offspring to make each individual offspring more likely to survive to reproductive maturity. In fact, there’s a natural mechanism that prevents a woman from getting pregnant immediately after she’s given birth precisely because to do so would make it less likely that her newborn would survive. Were it the case that getting pregnant as often as possible were the way to maximize the fitness of a woman, then this delay would not exist. Further, as human society has become more complex, or rather that the amount of energy necessary to ensure the continuation of gene-propogation has increased, our birthrate has decreased accordingly. So, we’ve naturally found a way to continue maximizing our fitness even as the relative fitness advantage of continuous-pregnancy has decreased. You might think that humans are the only species that’s done this, but that’s not the case at all. There’s a very well-known (inverse) scaling relationship between the amount of energy a species consumes and its reproductive rate. But, I suppose that if you wanted to argue semantics, you could claim that “as often as possible” has a meaning relative to the fitness-maximization itself. But, that’s circular 🙂
Comment #60 March 25th, 2006 at 6:01 pm
Scott said…
In other words: Darwinism is not a theory of group survival; it’s a theory of individual gene survival.
This is also not quite generally true. Altruistic behavior is a well-known violation of the idea that Darwinian natural selection is all about the individual and the individual’s genes. Why be nice to anyone if that might inconvenience your own chance of success? And yet, all social animals (and there are a huge number of them) exhibit altruism to varying degrees. The neat thing about altruism is that it seems to exist in a constant state of tension with the selfishness of individuals. In social animals, altruism appears to follow, primarily, familial lines. This, in turn, bolsters the argument that altruism arose from the fact that if a decrease in fitness of one individual is less than the relative increase in the fitness of a closely related individual, then the situation is favorable from the evolutionary perspective. That is, since the benefiting individual likely shares a large portion of identical genes as the benevolent individual, the genes themselves have increased their fitness relative to their non-cooperative competitors. At least, that’s how the argument goes. Basically, it boils down to defusing the zero-sumness of the evolutionary competition. There’s currently a lot of very interesting research being done in this area, since altruism isn’t as well understood as pure selfish behavior.
Comment #61 March 25th, 2006 at 6:38 pm
Thanks for the comments, Aaron! A few responses:
When I talk about selection pressures, I always mean what they were in the ancestral environment, not what they are today. A century from now, we’ll be custom-designing our children’s DNA sequences in Adobe BabyShop anyway. 🙂
But, I suppose that if you wanted to argue semantics, you could claim that “as often as possible” has a meaning relative to the fitness-maximization itself. But, that’s circular 🙂
I do want to argue semantics, and that is what I meant! 🙂 I’m learning that writing about Darwinism is hard — since if you put in every caveat that comes to mind you sound pedantic, but if you don’t someone inevitably jumps on you.
Altruistic behavior is a well-known violation of the idea that Darwinian natural selection is all about the individual and the individual’s genes.
No, no, no! The two are profoundly compatible.
The first reason they’re compatible is kin selection, as you correctly pointed out. Notice that I never said Darwinism is a theory of individual survival — I said it’s a theory of individual gene survival. If you were trying to maximize the propagation of a particular one of your genes, you’d care just as much about the copies residing in relatives’ bodies as about the copy residing in your own.
The second, more general reason, which you didn’t mention, is reciprocal altruism. “Always defect” is not a great strategy in an Iterated Prisoner’s Dilemma.
Comment #62 March 25th, 2006 at 11:54 pm
The better question, I think, is why do people rape at all?
Suppose rape were bad for the survival of the species. This must mean that it propagates genes that are rotten. This must mean that it would evolve away, no?
You seem to argue that rape might be propagating bad genes…but if that were true, then evolution says people wouldn’t rape at all. But if rape is good for the species, why do we (women) hate it? Shouldn’t we have evolved to like it? (As a side note, many women have rape fantasies – why?)
These questions are, at least to me, much more interesting than, “Why don’t I have a rocket launcher implanted in my pelvis?” I’m much more interested in knowing why evolution has led to the existence of men with a hidden propensity to do something to me, and then made me fear it so much. Perhaps that tension is good for survival?
A better question than even this: what is the point of consciousness? Why does it exist? Why do I wonder about the meaning of my life, and why does this question torture me? Creationists (and I’m not one) *do* harp on these points, because they are much better ones.
But the answer, I suspect, is that evolution is neither deterministic nor optimal. The wide variety of life on earth is proof. They could have teeth, but why? It’s so much simpler (and more advantageous) to do a decent job of preventing rape through social pressures. It’s not perfect, but it’s not bad either. (Rape is so common when these structures break down, as in times of war.) And the social structures that do this are great for the survival of the species.
Comment #63 March 26th, 2006 at 12:39 am
wumpus:
Suppose rape were bad for the survival of the species. This must mean that it propagates genes that are rotten. This must mean that it would evolve away, no?
(sigh)
Once again: rape is bad for the victim’s genes, good for the rapist’s genes (if he gets away with it).
No matter how bad a gene is for society, it will tend to propagate if it benefits the particular individuals who have that gene.
Natural selection doesn’t care about the welfare of society as a whole. It can easily produce outcomes that suck from a social standpoint. Indeed, that’s exactly what it’s done.
I wonder: why is such a simple point so hard for people to understand?
Comment #64 March 26th, 2006 at 3:41 am
The Wumpus replies:
You presuppose that rape is bad for the victim’s genes. Do you think that the person with whom the victim would “rather” reproduce is more genetically fit? What evidence?
Perhaps it is an evolutionary advantage that I reproduce with someone against my will! Perhaps the fact that I do not *want* to reproduce with the rapist (and the wider social behavior that accompanies my dislike) is an evolutionary vehicle!
I find, in my discussions (oh, so many!) with Creationist’s, that this is the crux of the issue! How can my personal preferences, which feel so real, contradict evolution?
Your question strikes at the root of this artifical dilemma. Is there a contradiction between what I feel and what is best from an evolutionary standpoint?
Does the existence of evil contradict evolution?
I feel that I can choose the best mate…but can I?
Why wouldn’t I, over the course of the evolution of my species, have developed the ability to choose the best mate? Maybe my choice doesn’t matter if rape is a possibility…
Comment #65 March 26th, 2006 at 4:28 am
Does the existence of evil contradict evolution?
LOL! Philosophers have debated for millennia whether the existence of evil contradicts the existence of a benign, omnipotent God. You’re the person I’ve ever seen who’s worried that evil contradicts evolution. 🙂
The answer to your question is: no, it doesn’t. I’ll prove it you mathematically, by exhibiting an evolutionary model in which evil conquers the world.
Assume everyone on Earth has one of two genes: good or evil. Every pair of people meets once to go hunting together. If two good people go hunting, then by cooperating they catch a buffalo, which they divide between themselves. If two evil people go hunting, their mutual distrust prevents them from cooperating, so they only catch some rabbits. If a good person goes hunting with an evil person, then they cooperate to catch a buffalo, but the evil person takes the buffalo for himself and leaves the good person with nothing.
So, two good people are always better off than two evil ones. But an individual is always tempted to evil, both to take advantage of the other guy and to avoid being taken advantage of himself.
The details of the scenario are not important. All that matters is that it formalizes the ordinary meanings of the words “good” and “evil.”
Now assume that the total population size is fixed, and that each person leaves a number of descendants proportional to the total amount of food he collects. Assume further that good people leave good descendants and evil people leave evil descendants.
Then it’s easy to show that, if there’s even a single evil person to begin with, eventually there will only be evil people left — the good ones will get wiped out.
It follows that the existence of evil does not contradict evolution.
If you still don’t understand this, unfortunately I don’t have time to argue about it further.
Comment #66 March 26th, 2006 at 4:29 am
Hi Scott,
Cool post. One question I’d like to know more about before plunging in is, how common is rape among non-human mammals? I know dolphins do it, but beyond that I’m in the dark. It seems like a female elephant seal would have a hard time fending off a male 3 times her mass, but I don’t know if they engage in rape or not.
I guess an even more fundamental question is, if one animal rapes another, how can you tell? Rape might be as common as dirt, and we just can’t tell it apart from normal sexual reproduction.
As for the absence of vaginal teeth, here’s a possibility I haven’t seen mentioned yet: not enough time. Most mammals other than humans have limited periods of fertility, so maybe most rapes occur outside of the breeding period and just aren’t a big problem. (On the other hand, “adaptive rapes” would ALL occur during breeding season. Anyone have any data on this?) Anyway, IF vaginal teeth were more useful for humans than for other animals, there would have been little reason for our non-human ancestors to evolve them, and (maybe) not enough time for us to evolve them yet. Before you pooh-pooh that as not much of an explanation, remember that your ultramobile, oh-so-sprainable ankles would make more sense for a climber than a runner. We ought to have hinge-style ankles, like ungulates or running birds, but we haven’t been down out of the trees long enough.
It occurs to me that vaginal contractions can be strong enough for the penis to get stuck, at least for a while. We might expect the precursor phase to actual teeth to start with something like that. But just trapping the penis doesn’t stop the ejaculate, and might actually encourage its release. So maybe the happy adaptive valley of toothy vaginas is on the other side of a ridge of inadaptive physiological reactions?
Here are a couple more ideas. One is like the “rare predator” effect that Dawkins invokes to explain why some fish aren’t better at getting away from the bad guys. Maybe there just aren’t enough rapes to create the necessary selection pressure.
Finally, maybe the fitness penalty (if any) involved in having a rapist’s baby is less than the penalty of missing that opportunity to reproduce. Especially since for most of human history getting knocked up early was a girl’s best way of signaling her worth to potential mates…
The asexuality problem bugs me too. Female cloning has evolved several times in desert lizards. They never radiate, and the consensus is that it’s an evolutionary dead end. Fine–but then why does it evolve in the first place? Diseases evolve so fast that these asexual lineages should never get off the ground, if disease is really an extinction-level problem.
Thanks for the fun,
Matt
Comment #67 March 26th, 2006 at 5:00 am
Thanks, Dr. V.! It was a pleasure to hear from someone who actually knows something about biology. 🙂
Comment #68 March 26th, 2006 at 5:32 am
Of course, mine was a rhetorical question. It doesn’t make sense to ask whether or not “evil” and “evolutionary” are contradictory — and that is precisely the point!
In fact, they cannot contradict one another unless we assume that evolution leads to an ethically favorable outcome. That assumption doesn’t exist. That is precisely point.
You still have not said why you believe that rape is necessarily disadvantagous (from an evolutionary standpoint) for the victim, and that is the critical point in your argument.
It would be lovely if science and ethics always met, but they don’t…and what would it mean if they did? This is the reason that scientists, above all, should be ethically upright; scientists should see and respect ethics for the strictly unscientifict (but still objective?) discipline that it is.
I think this is an important point to address when battling creationists. They are often blind to science, but they have a deep understanding of ethics. (I’m not sure that creationists even know what science IS.)
You must be prepared to say, “Yes, the existence of rape might give some evolutionary advantage. I accept the existence of rape (in some sense) scientifically, but I reject it ethically.” Creationists have an explanation for evil, but do we? Of course not, because evil is not in the domain of science.
I regret that you don’t have time to discuss this further.
Comment #69 March 26th, 2006 at 11:23 am
Similar questions are raised by parts of Stephen Jay Gould’s “Wonderful Life” (a wonderful book, by the way). For example, bilateral symmetry appears to be an extremely popular form among post-Cambrian animals, whereas there seems to have been greater diversity (e.g., 5-way symmetry was common) among pre-Cambrian fossils.
Perhaps the lack of greater recent morpholical diversity and “vagina dentata” could both be explained by the locations of the relevant genes. That is, perhaps the genes are located in such “critical” regions that the mutations necessary to achieve these effects will virtually always result in non-viability. Obviously a great deal more exploration of animal genomes and gene expression is necessary to see whether this speculation holds any water.
Comment #70 March 26th, 2006 at 11:28 am
Oh, and one other comment re speculation about ways that the female orgasm might confer evolutionary advantage:
It seems to me by far the simplest and most obvious explanation is that folks will tend to do something more often if it feels really, really good.
Comment #71 March 26th, 2006 at 12:44 pm
It seems to me by far the simplest and most obvious explanation is that folks will tend to do something more often if it feels really, really good.
Again: the question is why it feels good.
Comment #72 March 26th, 2006 at 1:51 pm
. . I cannot seem to figure out how to reply to a comment (can I, without an account here?). Oh well. Anyway –
I said: And vaginas don’t have teeth because they’d somewhat complicate the process of giving birth.
And you said: That’s a novel theory! But it still doesn’t deal with retractable teeth.
Actually, I think it does, or else changes the question to “why don’t female humans have an entirely different pelvic anatomy?” A normal full-term birth uses up just about all the space available in the pelvis. Teeth, retractable or otherwise, don’t stretch or squish very well. For a female with a toothy vagina to give birth successfully, you’d need a wider pelvic opening, or a jointed pelvis (or smaller newborns, but that’s a whole ‘nuther can of worms there). If you kept the present single-structure design, at its present size, and just made the hole in the middle bigger, you’d make the bone as a whole more fragile – obviously, not a good plan. Anything else, would essentially require re-working the entire anatomy of the female from the waist down (as changing the pelvis changes the hips, which would put different demands on the knees, etc., etc.) As none of these changes would be particularly beneficial to the male of the species, for them to succeed you’d have to have a far greater degree of sexual dimorphism than presently exists in humans. In other words, it’s not just a matter of inserting teeth, and I’d say teeth just aren’t a dire enough need to result in such drastic changes.
Better question is, rather than teeth, why not just have greater voluntary muscle control and strength at the entrance? If you’re not so much worried about preventing penetration (and that’d have to have already occurred for teeth to be any use, either) as preventing ejaculation, then cutting off blood flow to the penis would work just as well, and that could be accomplished just by squeezing really, really hard.
But I concede your point re: Genghis Khan.
Comment #73 March 26th, 2006 at 2:12 pm
Better question is, rather than teeth, why not just have greater voluntary muscle control and strength at the entrance?
That is an excellent, excellent question. The vagina can contract hard enough to keep the penis out in the first place. An acquaintance of mine was so tense about her first time that her boyfriend couldn’t achieve entry. She had to see a doctor and get some topical anesthetic to relax her enough for penetration to take place. As a copulation defense, vaginal tetany would be a lot easier to achieve than teeth. And yet we don’t see it. Perhaps there is just no selection pressure at all in this direction.
Comment #74 March 26th, 2006 at 2:52 pm
Sonya: Thanks!! On reflection, I think you’re right about the large body plan changes that a biting vagina would entail.
As you probably realized, I mainly used biting vaginas as a vivid (and if I might say so, humorous) way to illustrate my real question: namely, why haven’t women evolved better defenses against unwanted pregnancy, of some sort or another? Stronger muscles at the vaginal entrance would be one example; a movable flap between the vagina and egg would be another.
Comment #75 March 26th, 2006 at 3:29 pm
> Perhaps there is no selection pressure at all in this
> direction.
The fact that women can be raped could be seen as a survival mechanism in itself. When men are at war, they frequently slaughter the males, but rape the females and leave them alive. Why bother, if the woman can just close her vaginal flap and prevent impregnation?
So, in most cases, women have a fair amount of choice. In the cases where they don’t have a choice, the fact that they can be raped might help them out.
From a recent article about the Sudan:
“Over 100 women were raped, six in front of their fathers who were later killed….A further 150 women and 200 children were abducted.”
Here’s a quote from a woman who was raped:
“[They] said, ‘Black girl, you are too dark. You are like a dog. We want to make a light baby.'”
The women, because they can be forcibly impregnated, are surviving a concentrated attempt at ethnic cleansing! And their genes will survive it, too. If that girl had a flap (and the will to slam it shut) she’d be dead.
But what’s the benefit of rape-ability in a “civilized” culture? Probably not much, but it’s not a big disadvantage when women have some pretty good alternative methods to avoiding rape – no dark alleys, no hitching, no pre-opened beer cans, etc. Will that flap evolve if ethnic cleansing goes away? Probably not, becuase other preventative methods are evolving.
Anyway, what’s the point of a rapist who kills his victim?
Comment #76 March 26th, 2006 at 3:55 pm
As you probably realized, I mainly used biting vaginas as a vivid (and if I might say so, humorous) way to illustrate my real question: namely, why haven’t women evolved better defenses against unwanted pregnancy, of some sort or another?
Because there’s no evolutionary benefit to recreational sex, except that it results in pregnancy – or, now I think about it, that it keeps the male around to help provide for the offspring. And actually, women do have a natural, though not 100% reliable, defense against pregnancy – breastfeeding. It suppresses ovulation. Thus a woman can have all the recreational sex she wants while she’s breastfeeding an infant, and in poorer and less technologically advanced cultures it’s not uncommon for a woman to nurse her child until he or she is around 5 years old. Her mate is thereby given incentive to stay around during the offspring’s most vulnerable period, and once that period of total dependency is over (i.e. the child is weaned), she can get pregnant again.
To be completely cold about it, I suppose the system works on the basis that if a woman bears the child (voluntarily or otherwise) of a sub-standard mate, i.e. one who is either not a good provider or doesn’t survive long enough to provide, those genes will be weeded out because the offspring will die. If the offspring doesn’t die, then it’s a testament to the female’s hardiness, and the merit of her genes outweighs the lack of merit of the father’s. Of course if the child doesn’t survive then the female’s fertility is “wasted” while she’s carrying and caring for it, but that works too – it’s a mark against *her* genes, that she lacked either the discretion to choose an appropriate mate or the physical prowess to fight off an unsuitable one (or perhaps, that her mate lacked the strength to defend his claim?). Not pleasant, but functional.
So the short answer is that the system hasn’t been fixed because it’s not broken. The perception that women need to have greater control over their fertility is cultural. (I’ve got a whole ‘nuther rant about how our culture is idiotic in its management of fertility, but that’s a different subject.)
Comment #77 March 26th, 2006 at 6:28 pm
I think Sonya is pretty close to right on, in her observation that:
…the system hasn’t been fixed because it’s not broken. The perception that women need to have greater control over their fertility is cultural. (see “radiation suit” disclaimer below!!!)
The absolute prerequisite for gene propagation is reproduction. I suspect that if we worked out the math, we’d find that the best strategy for a gene is to maximize its host’s offspring. In other words, the prime imperative for a female’s DNA is to keep her pregnant as often as possible — as long as pregnancy does not substantially decrease the survival probability of pre-existing or [possible] future offspring!
To first approximation (in this model), the father’s genes are irrelevant. The genes are “trying” to get their host pregnant as quickly as possible. Any gene that encourages non-conception as opposed to conception (with any mate!) is at a disadvantage.
This begs the question of why so many animals have selective “choice” mechanisms. My conjecture: because it’s cheap and easy. A gene that motivates its host to choose the best of N mates has a slight advantage. As an informational/cognitive mechanism, this scheme has very low energy cost, so there’s no reason it wouldn’t evolve.
Why is it only a slight advantage? Because the gene pool is pretty damn good. All the males are stupendous badasses to begin with, otherwise they wouldn’t have made it this far. So the whole mate-selection business is just an energetically cheap way of getting 1% better fitness.
A selective-conception mechanism, on the other hand, would not allow choice between mates — it would allow the female to choose no mate, at least for the time being. If she spends 10% of her time choosing not to conceive, this might reduce her total offspring by 10%! This is a horrendous fitness cost, and such a gene would be stomped out of existence.
I now need to don Scott’s “radiation suit,” and point out:
1) Sonya’s [quoted] statement could rather easily be taken as a social / cultural / moral statement, in which context it would be offensive as all hell. I interpret (and support) it in an evolutionary context only: “women need X” -> “a female organism’s genes benefit from X”.
2) This discussion is orthogonal to morality. Women should not stay constantly pregnant unless they want to. If I were going to moralize, I’d say they shouldn’t even if they do want to. *grin*
3) The entire scenario I outlined above applies only to the pre-paleolithic era. It’s absurd in today’s environment, where reproductive choice dominates reproductive success (= # of offspring). However, virtually every known species including homo sapiens evolved exclusively in that pre-paleolithic environment.
P.S. Note to Scott: choosing the maximally vivid and controversial way of asking “Why didn’t females evolve more control over conception?” may have been suboptimal, since e.g. the flap mechanism in Hypothesis 2 is probably unconditionally superior (unlike teeth, it doesn’t prevent non-impregnating rape… but that might actually enhance fitness, as seen in the horrifying examples above). It did get a lot of attention, though…
Comment #78 March 26th, 2006 at 8:04 pm
Robin:
All the males are stupendous badasses to begin with, otherwise they wouldn’t have made it this far. So the whole mate-selection business is just an energetically cheap way of getting 1% better fitness.
LOL! I wonder if any female readers will beg to differ with that hypothesis…
Comment #79 March 26th, 2006 at 9:00 pm
1) Sonya’s [quoted] statement could rather easily be taken as a social / cultural / moral statement, in which context it would be offensive as all hell. I interpret (and support) it in an evolutionary context only: “women need X” -> “a female organism’s genes benefit from X”.
While I have been known to be offensive as all hell, especially on this subject, I was not intending to be with that statement. I meant it in an evolutionary context only. I’d say keeping track of the context is fairly crucial to this whole conversation, if we want to avoiding being both offensive and completely ridiculous (I mean, we’re discussing vaginas with teeth, folks). 🙂
Comment #80 March 26th, 2006 at 9:07 pm
I’m not sure what exactly to say about this, but it’s relevant to the discussion abuot rape and evolution. Some women get sexually aroused during rape; I’ve heard some even orgasm. I am NOT saying they enjoy it – it’s an uncontrollable reaction of the body even when they are terrified and hating the experience. I don’t know what percentage of rape victims that is, but it’s very difficult for them to deal with, and I’ve assumed it’s an unfortunate byproduct of our bodies essentially liking to propagate.
Comment #81 March 27th, 2006 at 12:27 am
If a good person goes hunting with an evil person, then they cooperate to catch a buffalo, but the evil person takes the buffalo for himself and leaves the good person with nothing.
Or, in some cases, the evil person shoots the good person in the face.
Comment #82 March 27th, 2006 at 7:40 am
“Again: the question is why it feels good.”
Hmm, should have thought that would be obvious. Anyone for whom it feels good will likely do it more often, thus tending to get preggers more often, thus propagating more offspring, who in turn have a better chance of possessing the “feel good” genes…. In other words, orgasm should confer a selection advantage without having to go through speculation about “maybe it increases sperm retention.”
Comment #83 March 27th, 2006 at 12:33 pm
Simple answer: Nature doesn’t care if ADN is transmitted with disagreement or agreement.
Comment #84 March 27th, 2006 at 12:40 pm
Oh, and one additional thing about “if it feels good, do it” in relation to selection advantage:
To the extent that desirability in men parallels fitness, and that women are more likely to achieve orgasm with desirable partners, this should reinforce female selection of desirable/fit partners. This would be a selection mechanism favoring positive traits rather than minimizing negative ones.
Comment #85 March 27th, 2006 at 6:24 pm
Scott,
thanks for the fine imagery – “Biting Vaginas”.
In nature, I don’t know if rape occurs often but I think it’s probably harder to do. From nature shows they often mention that the male approaches the female to see if she is receptive and if she isn’t the male goes away. I would think that the reason for this is that a female animal is much more dangerous to the male of the species because that female probably has sharp teeth and claws. Again from nature shows they seem to indicate that animals (even lions) fear injury because it would affect their ability to feed themselves and/or they could also die.
Comment #86 March 28th, 2006 at 12:05 am
Is there any plausible route to evolving retractable teeth/claws/stingers without first going through an intermediate nonretractable stage? I don’t know of any cases in real evolutionary history where this is thought to have occurred (for example, cats evolved from ancestors with nonretractable claws), and in your scenario nonretractable teeth would pose some obvious problems.
Comment #87 March 28th, 2006 at 12:24 pm
This post illustrates the fallacy that evolution always finds ideal solutions, rather then local maxima. The fact that something didn’t evolve doesn’t make it a bad idea.
Also, being raped doesn’t really affect a woman’s ability to pass along her genes at all. You might as well ask why we haven’t evolved USB ports to download data directly to our brains, it would certanly be convienent.
Comment #88 March 28th, 2006 at 4:41 pm
Artificial teeth:
http://en.wikipedia.org/wiki/Anti-rape_female_condom
Comment #89 March 28th, 2006 at 11:26 pm
Who says vaginas don’t have teeth?
http://www.vaginaswithteeth.org
Comment #90 April 1st, 2006 at 9:34 pm
Wow… have I ever been away for awhile. Okay. I’ve got a few thoughts on the biting vagina thing…
1) I think The Wumps’ question was a great one, and very relevant: why does rape itself exist? Here’s my thinking on the matter. Human genetic makeup has changed very little since we evolved from chimps (if I’m remembering my biology classes right). Evolution takes time… LOTS and LOTS of time. Thus, the changes that we have observed in humans since our chimpanzee days are largely of a social/cultural nature. So, according to our genetic makeup, male aggression may actually be seen as a favourable quality as it is in the animal kingdom (the alpha male). While our social structure may not condone rape (debatable), our genes do. Therefore, a biting vagina would not be an evolutionary advantage. (Note: I can’t believe I’m arguing for the adaptiveness of rape. I feel dirty).
2) It was my impression that Darwinian evolution worked through a process of spontaneous mutation… small changes over a long period of time. How can we slowly evolve teeth in our vaginas? More to the point, I thought Darwinian evolution was supposed to be random… small random mutations that either work or don’t work. OR traits that are normally distributed in the poulation that, due to changes in the environment, become more or less adaptive (i.e. the big beaked/small beaked bird example). The evolution of a biting vagina would be more of a Lamarckian question, since this would be an all-or-nothing change in direct response to the society that can be passed on to offspring. This sort of theory was tried out in the former USSR to breed new generations of communtists. Not surprisingly, it didn’t work.
3) Are you actually a fan of Popper? If so, I can’t see how you can resign yourself to both falsifiability and Darwinian evolution. Evolution, as Darwin concieved of it, can’t be falsified. In fact, Popper himself even argues against it in his writings. It’s right up there in his mind with Freudian Psychoanalysis (which you poo-pooed near the beginning of this comments section). This is exactly why I have a problem with Darwinian evolution (that and the evils it has spawned in psychology due to the misrepresentations of Darwin’s original ideas on the part of Spencer and Galton). So, my question: are you actually a fan of Popper? If so, how do you reconcile the two ideas? If not, well, nevermind. 🙂
Comment #91 April 1st, 2006 at 11:07 pm
So if teeth in vaginas couldn’t have evolved, how could the teeth in my mouth have evolved?
Evolution can’t be falsified? Oh wait–that’s religion…
Comment #92 April 2nd, 2006 at 10:57 am
Anonymous 11:07 (01/04/06):
“Evolution can’t be falsified? Oh wait–that’s religion…”
1) No, evolution can’t be falsified. Can you think of a way to empirically show that evolution is wrong? Evolution may be verified by our observations, but that does not mean that it is a falsifiable theory. Unfortunately, there are a great many contradictory/wrong theories out there that can be verified using the scientific method. Hence Popper’s insistence on falsification as the new scientific crtierion.
2) Science isn’t a religion? Oh dear. Science may be a useful religion, but it is still simply that. Suggestion: read Feyerabend’s “Against Method: Outline of an Anarchistic Theory of Knowledge.” Rather than reading the whole thing, pages 295-309 will get the point across. Amazing read. It’ll blow your mind. Actually, I highly recommend that anyone involved in the sciences read it. I’ll leave you with the quote that Feyerabend starts off the chapter with: “…science is much closer to myth than a scientific philosophy is prepared to admit” (p. 295).
Comment #93 April 3rd, 2006 at 5:30 am
Miss HT:
Wow… have I ever been away for awhile.
LOL, I knew you’d have something to say! But as it happens, I disagree with all three of your points.
While our social structure may not condone rape (debatable), our genes do. Therefore, a biting vagina would not be an evolutionary advantage.
Here you fall into the same trap as several previous commenters: namely, you fail to ask, “evolutionary advantage to whom?” If a gene for biting vaginas were sufficiently advantageous for the females who had it, then it would spread regardless of its effects on the population as a whole.
It was my impression that Darwinian evolution worked through a process of spontaneous mutation… small changes over a long period of time. How can we slowly evolve teeth in our vaginas?
If this argument were valid, it would work not only against teeth in vaginas, but also against teeth in mouths! Where did the first teeth come from, anyway? Suffice it to say that complex adaptations, like teeth, eyes, brains, etc., can and do arise via sequences of tiny mutations. Dawkins, and for that matter Darwin himself, have both written lucidly on this point. Two major ways it happens are (1) “exaptation” of organs that were originally meant for something else, and (2) lots and lots of time.
Are you actually a fan of Popper? If so, I can’t see how you can resign yourself to both falsifiability and Darwinian evolution. Evolution, as Darwin concieved of it, can’t be falsified.
Bullshit. If it were found, for example, that exactly the same finch species arose indigenously in both the Galapagos Islands and in Australia, with nothing like it anywhere in between, that by itself would overthrow Darwinism (in favor of either special creation or else some teleological theory).
As for Popper, my opinion of him is the same as my opinion of most philosophers: namely, that everything he said is either obvious or false. I agree with the obvious things he said, and disagree with the false ones. 😉
Comment #94 April 3rd, 2006 at 5:34 am
Miss HT:
Science isn’t a religion? Oh dear. Science may be a useful religion, but it is still simply that. Suggestion: read Feyerabend’s “Against Method: Outline of an Anarchistic Theory of Knowledge.”
I see that my project of saving you from the clutches of idiots will take longer than I’d expected. 🙂