Why Is the Human Vagina So Big?
为什么人类阴道那么大
We are obsessed with penis and testicle size. Yet, we can barely say “vagina” and when we do we’re usually talking about the vulva.
我们总是着迷于阴茎和睾丸的尺寸，却极少谈及“阴道”，就算我们提到了，一般也只是讨论外阴。
Everyone’s come across some article somewhere on-line that is thrilled to share how big human penises really are, for primates, and to explain why they evolved to be so big. It’s not really the length, but the girth. Alan Dixson is your go-to on this. He’s conservative in his assessment of the literature on penis size and even he concedes that human penis “circumference is unusual when compared to the penes of other hominoids (apes)” (p. 65 in Sexual Selection and the Origins of Human Mating Systems).
每个人都见过，网上的一些文章在兴奋不已地告诉你，人类的阴茎在灵长类中有多大，为什么会进化成这么大。其实所谓的大，不是指长度，而是指茎围。说到这个话题，你去问Alan Dixson就准没错。他对有关阴茎大小的文献一贯持比较谨慎的态度，但连他也承认，人类的阴茎“周长和其他人猿的阳具相比是个异数” （见《性选择与人类繁衍系统起源》第65页）
A favorite explanation for the big phallus is female mate choice, that females selectively make babies with males who have larger and, presumably, more pleasurable semen delivery devices. This is backed up by studies. When life size projections of naked men are shown to female subjects, they say they find the ones with bigger ones to be more attractive. [This is exactly how mate choice works where I live, how about you?]
对阳具大型化的一个比较受欢迎的解释是雌性交配偏好，也就是说雌性倾向于选择与有着较硕大、想来也较受用的“精液注射器”的雄性交配产子。这一理论得到了一些研究的支持。有研究让女性受访对象看真实大小的裸男幻灯片，她们纷纷表示阳具伟岸的男性比较有吸引力。（这完全符合我日常所见的择偶选择，你呢？）
Other explanations include male competition. If you can deliver your package to the front yard but the other guy can deliver to the front door, his is more likely to be carried inside the house first. Or, if he can steal away what you just delivered, then, again, his package has yours beat. Thanks to his big penis he’s more likely to pass on his winning penis genes than you are to pass on your loser penis genes. Loser.
雄性竞争也是一种解释。如果你只能把包裹投递到院子里，但另一个人可以把包裹放到屋门前，那他的包裹先进屋的几率就高一些。又或者，如果他可以偷走你刚送的包裹，那他的包裹也一样打败了你的。因为器材比较大，他延续他那“赢茎”基因的可能性比你延续你那“输茎”基因的可能性也就比较大。于是你就完蛋了。
All this is just terribly fun to write about and I’m not even going nuts (gah) like they do. And they do. They really do. And all over the Internet they do: “Evolution of human penis” gets 53,000 hits just on scholar.google alone, and about 832,000 on Google.
写这些东西真是好玩死了，而我又不会像他们那样疯狂，咔咔。他们真是挺疯的，不骗你。男人在网上有这么疯：搜索“人类阴茎的进化”，仅仅在谷歌学术上就得到了53,000个结果，在整个谷歌上则得到了832,000个。
But doesn’t it make sense that for a penis to be somewhat useful it has to be somewhat correlated to vagina size?
但是，如果阴茎要发挥功能，难道不是应该和阴道的大小联系起来才说的通吗？
I’m talking about all penises in the universe and all vaginas too. Sure there’s variation, but a penis can’t be too wide. It helps to be long, probably, but it can’t be too long.
我在讨论的是地球上所有的阴茎，和地球上所有的阴道。当然它们会有差异，但阴茎也不能太粗。长应该是有好处，但也不能太长。
So neither pleasure nor psychology need matter at all, just function associated with some sort of fit. Pleasure and psychology are never invoked to explain penis morphology in other animals. If anything, it’s the cornucopia of horrifying, not pleasing, animal penises that begs for evolutionary explanations.
其实肉体欢愉和心理需要都根本不重要，重要的只是与大小匹配相关的功能。肉体欢愉和心理感受从来就没有被拿来解释其他动物的阴茎形态。如果非要从进化论的角度看，就要去解释太多种并不讨喜，反而可怕的动物阴茎了。
Wouldn’t you explain the size and shape of the key by the size and shape of the lock? So wouldn’t it be a little more scientifically sound to hypothesize that the human penis is sized and shaped like that because it fits well into the human vagina?
你在解释钥匙的大小和形状的时候，不是以锁的大小和形状为参照的吗？因此，人类阴茎之所以是如此的大小和形状，是为了要匹配人类的阴道，这种猜想在科学上不是比较合理么？
Sure, it gets chicken-and-eggy or turtles-all-the-way-downy, but c’mon. Isn’t it a bit obvious that the privates that fit inside the other privates are probably correlated? You’d think that even the people who have never had intercourse would default to this explanation for the evolution of the human penis.
当然，这会演变成一个鸡先蛋先，又或者是龟下有龟的问题【译注：”It’s turtles all the way down”来自一则古老的轶事，体现逻辑上的无限递归，后来成为一句玩笑话，用来表达表面立于不败之地，而实则回避逻辑问题的境况】。不过，拜托，互相契合的灵长类体征具有相关性，这不是很明显吗？你应该会同意，就算没有性经验的人，不需多想也会接受这个有关人类阴茎进化的理论吧。
But we’re rarely, if ever, told that human penises are relatively girthy because human vaginas are. It’s always about male competition or female preference.
但我们极少，甚至从没有听人提过，人类的阴茎之所以比较粗大，是因为人类的阴道比较粗大。大家总是在研究那些雄性竞争和雌性偏好的理论。
Sure, we may be a little weird compared to our close relatives for not having a baculum (penis bone), and maybe that’s the sort of thing you want to explain for whatever reason, but does human penis size and shape need a uniquely human story?
人类阴茎没有骨骼，和人类的近亲相比这也许显得有些奇怪，你可能会出于种种原因想为这一现象找个解释。但人类阴茎的大小和形状有别于其它动物，真的需要一个独特的解释吗？
Assuming it’s correlated to the vagina like it probably is in many other species,* then no it doesn’t… unless the size and shape of the human vagina has an exceptional story.
有不少其他动物的阴茎大小和形状很可能和它们的阴道相关，假设人类也是如此，那除非人类阴道的形态有异于其它动物，否则人类阴茎的形态不应该有什么特别。
[水禽雌雄生殖器官协同变异的图例。标星型的为雄性生殖器，箭头指向的是女性生殖器。图片来自“水禽雌雄生殖形态的协同进化”。DOI编码: 10.1371/journal.pone.0000418]
Does it? We wouldn’t know. There are zero (look!) articles titled “Why is the human vagina so big?”
究竟有没什么特别呢，我们不知道。从来都没有文章（你自己看！）以“为何人类的阴道那么大”为题。
Until right now.
直到现在才有。
Here we go. If we were going to answer it the same way we’ve long explained the human penis, and other animal penis shapes, then we’ve got a few ideas…
来吧，如果以我们长期以来解释人类和其他动物阴茎形态的思路，来回答这一问题的话，我们可以有如下一些解释……
Because walking upright made the vagina conspicuous and males thought a bigger vagina was better. Because big vaginas outcompete small ones at catching sperm. Because of male pleasure from coitus with a big vagina. Because of heat dissipation or thermoregulation. Because of a tradeoff with brain size.
因为直立行走让阴道外露，雄性认为阴道大一点比较好。因为大点的阴道比小点的更易于捕捉精子。因为大一点的阴道令雄性性交更舒服。因为有利于散热和调节体温。因为这是针对脑量增大的折衷方案。
And of course, we’d need to demonstrate that the human vagina is in fact larger, relative to body size, than the vaginas of other primates. Regardless, a sound answer to the question of vagina size and shape focuses on childbirth, wouldn’t you say? She’s got to be big enough to push out a baby and, for humans, it’s a great big baby.
当然，我们需要证明人类阴道相对于身体的比例，比起其它灵长类动物来说的确要更大。无论如何，难道你不觉得要回答人类阴道大小形状的问题，重点应该放在分娩上吗？阴道得足够大才能把婴儿生出来呀，人类婴儿的个头可大得很。
[红毛猩，大猩猩，黑猩猩与人类的对比。这些数值偏离了灵长类总体的回归分析。数据来自Dunsworth等人，2012年，PNAS第 109(38)：15212-15216]
So if there’s an exceptionally human story for the great big human penis, that exceptional story originates not in a woman’s orgasms, not in her pornographic thoughts or her lustful eyes, but in her decidedly unsexy “birth canal.”
所以如果人类阴茎硕大有什么特别原因的话，那原因既不是来自女人的性高潮，也不是来自女人的淫思欲眼，而是来自于那毫无性感可言的“产道”。
And I dug up a nice little note to explain this to us all written by Dr. Bowman, a gynecologist, back in 2008 for the Archives of Sexual Behavior which is magnificent. It starts out giving the only vagina-size-based, not to mention childbirth-based, explanation for human penises that I can find in the literature (which is thankfully cited by Dixson in his book mentioned above). But it still manages to bring the explanation beyond the vagina and onto another proud triumph: “In sum, man’s larger penis is a consequence of his larger brain.”
我找到了妇科医生Bowman于2008年发表在《性行为档案》上的一篇文章，该文很好地向大家解释了上述问题。文章开始以阴道大小和分娩需要为切入点来解释人类阴茎的大小，这是我能找到的以阴道大小来解释阴茎大小的唯一文献，从分娩需要着眼就更不用说了。这要感谢Dixson在前文提到的书中引用了这一资料。Bowman在文中还站在一个比阴道更高的层次，去解释这个问题：“总而言之，人类阴茎巨大是脑量增加的后果”。
After you clean up the coffee you just spat onto your computer screen, you can read it all for yourself by clicking on the link up there (or emailing me for the pdf).
你可以先把喷到电脑上的咖啡抹干净，然后点击上面的链接，通读一下那篇文章（想要pdf格式的可以发邮件给我）。
Guess who didn’t read it? That study in PNAS, mentioned above, that showed women naked penises, got a high attractive score for the big ones, and thinks that’s evidence for mate choice now, today, let alone back when (I’m going to speculate that) women had a tiny bit less of it.
你猜谁没有读过那篇文章？就是文章开头提到的那项研究的研究者【编注：指本文第三节提到的“让女性受访对象看真实大小的裸男幻灯片”的那项研究】，他们把阴茎赤裸裸地呈现给女人看，让那些大家伙拿到高分，然后认为拿到了交配偏好在当代的证据，至于过去女人眼福稍浅（我只是猜的）的年代是什么情况，就更不用废话了。
Point is, the literature rages on with the special explanations for the big penis with nary a big vagina in sight.
重点是，各路文章热火朝天地为大阴茎找了各种特别的原因，却对大阴道视而不见。
But you heard it here, at least.
但起码你在这里听说了。
Childbirth is why the human vagina is so big and, consequently, why the male penis is so big. It’s pretty straightforward. Yet we’re still left scratching our heads as to why the penis question endures.
分娩导致了人类阴道如此巨大，进而导致人类阴茎如此巨大。这很直观。然而大阴茎的话题经久不衰，这很令我们挠头。
Is evolutionary science averse to big vaginas?
难道进化研究是反大阴道的么？
Does nobody love a big vagina?
难道就没人喜欢大阴道么？
Because that’s just ridiculous. Everybody came from one.
这很荒谬，每个人都是从那儿出来的呀。
P.S. Unfortunately a few scholar.google searches led me to find no cross-species comparisons of mammalian vagina lengths or any vaginal measures. It may be out there, but I haven’ t found it. I found some measures for bitches… DOGS! And some heifers… COWS! So I’ve got to compile some data if I’m to do this properly. Baby size might be a way to do this.
P.S. 我在谷歌学术搜索了一下，可惜没有找到不同哺乳动物阴道长度或尺码的对比。也许有，但我找不到。我倒是找到了狗娘的尺码……是真的母狗啦！还有牛逼的尺码……也是真的母牛啦！所以如果要认真对比的话，我得收集整理一些数据才行。通过分析婴儿的大小可能也是一个办法。
P.P.S. p. 73 in Dixson has Figure 4.3 with nine primate species’ penile and vaginal lengths plotted. Thanks Patrick C. for reminding me where I’d seen something like this and where to point readers!
P.P.S. Dixson书中第73页的图表4.3，列出了九种灵长类动物的阴茎与阴道的长度。谢谢Patrick C.提醒我曾经看到过这样的图表，让我可以告诉读者上哪里找。
翻译：小册子（＠昵称被抢的小册子）
校对：林翠（＠cwlinnil）
编辑：辉格@whigzhou