從進化角度看女性性高潮之謎

An eye is for seeing, a nose is for smelling. Many aspects of the human body have obvious purposes.

眼睛是用來看東西的，鼻子是用來聞氣味的。人體的很多方面都有明顯的用途。

But some defy easy explanation. For biologists, few phenomena are as mysterious as the female orgasm.

但有些地方令人費解。對生物學家來說，幾乎沒有什麼現象能像女性性高潮那麼神祕。

While orgasms have an important role in a woman’s intimate relationships, the evolutionary roots of the experience — a combination of muscle contractions, hormone release, and intense pleasure — have been difficult to uncover.

儘管性高潮在女性的親密關係中發揮着重要作用，但這種經歷——同時出現肌肉收縮、荷爾蒙分泌和強烈的快感——的進化根源卻難覓蹤跡。

For decades, researchers have put forward theories, but none are widely accepted. Now two evolutionary biologists have joined the fray, offering a new way of thinking about the female orgasm based on a reconstruction of its ancient history.

幾十年來，研究人員提出了各種理論，但沒有一種理論得到廣泛的認可。現在，又有兩名進化生物學家加入爭論，提出了一種新的思考女性性高潮的方式，它的基礎是再現其古老的歷史。

On Monday, in The Journal of Experimental Zoology, the authors conclude that the response originated in mammals more than 150 million years ago as a way to release eggs to be fertilized after sex.

週一，兩名作者在《實驗動物學雜誌》(The Journal of Experimental Zoology)上推斷，女性性高潮這種反應起源於逾1.5億年前的哺乳動物，當時是爲了排出卵子，讓其在性行爲結束後受精。

Until now, few scientists have investigated the biology of distantly related animals for clues to the mystery.

此前，幾乎沒有科學家通過研究屬於人類遠親的那些動物的生物學，來尋找解開這個謎團的線索。

“For orgasms, we kept it reserved for humans and primates,” said Mihaela Pavlicev, an evolutionary biologist at University of Cincinnati College of Medicine and an author of the new paper. “We didn’t look to other species to dig deeper and look for the origin.”

“對於性高潮，我們過去認爲它僅限於人類和靈長目動物，”辛辛那提大學醫學院(University of Cincinnati College of Medicine)進化生物學家、新發表的那篇論文的作者之一米哈埃拉•帕夫利塞夫(Mihaela Pavlicev)說。“我們沒有爲了更深入地挖掘和尋找起源而研究其他物種。”

The male orgasm has never caused much of a stir among evolutionary biologists. The pleasure is precisely linked to ejaculation, the most important step in passing on a male’s genes to the next generation. That pleasure encourages men to deliver more sperm, which is evolutionarily advantageous.

男性的性高潮從未在進化生物學家中引起這麼大的波瀾。這種快感被精確地和射精聯繫在了一起。射精是將男性的基因傳遞給下一代的過程中最重要的一步。這種快感鼓勵男性分泌更多精液，從進化的角度來說這是有好處的。

For women, the evolutionary path is harder to figure out. The muscle contractions that occur during an orgasm are not essential for a woman to become pregnant. And while most men can experience an orgasm during sex, it’s less reliable for women.

對女性來說，相關進化過程更難釐清。性高潮過程中發生的肌肉收縮，並不是女性懷孕必不可少的。並且儘管大部分男性都能在性交期間體驗一次性高潮，性高潮對女性來說卻沒那麼可靠。

In a 2010 survey, 35.6 percent of women said that they hadn’t had an orgasm the most recent time they had sex. Part of the reason for this is anatomy: the clitoris is physically separated from the vagina.

在2010年的一項調查中，35.6%的女性稱在上一次性生活中未達到性高潮。造成這種現象的部分原因在於人體結構：陰蒂和陰道在位置上是分開的。

Still, a number of scientists suspect that the female orgasm serves some biological function favored by natural selection. They just need to figure out what it is.

但仍有大量科學家懷疑，女性性高潮具有某種生物學功能，該功能得到了自然選擇的青睞。他們只需要找出是什麼功能。

“My gut instinct is that something that matters so much at an emotional level — the intense pleasure of orgasm — would seem to have reproductive consequences,” said David A. Puts, an evolutionary anthropologist at Pennsylvania State University.

“我的直覺是，在情感層面上——高潮的強烈快感——這麼重要的一件事，似乎應該產生繁衍的後果，”賓夕法尼亞州立大學(Pennsylvania State University)的進化人類學家戴維•A•普茨(David A. Puts)說。

Many hypotheses have been put forward. Dr. Puts and his colleagues have carried out studies to test the possibility that orgasms increase the odds that a woman’s eggs are fertilized by a genetically attractive male.

已有許多假說涌現出來。普茨博士及其同事進行了研究，目的是檢驗一種可能性：高潮會增加基因出色的男性讓女性卵子受精的機率。

Elisabeth A. Lloyd, a philosopher at Indiana University, isn’t buying it. In 2005, she published a book called “The Case of the Female Orgasm,” in which she reviewed 18 published theories about its function.

這並沒有說服印第安納大學(Indiana University)的哲學教授伊麗莎白•A•勞埃德(Elisabeth A. Lloyd)。在2005年，她出版了一本書，名爲《女性性高潮的問題》(The Case of the Female Orgasm)，其中對已發表的有關性高潮功能的18種理論進行了綜述。

None had strong evidence in its favor, she concluded, and many were undermined by other findings about human sexuality. Years of further research have only strengthened her skepticism.

她得出的結論是，沒有一種理論提供了有力的證據，其中不少還遭到了有關人類性行爲的其他一些研究成果的削弱。多年的進一步研究讓她的疑慮有增無減。

Dr. Lloyd thinks the best explanation for the female orgasm is that it hasn’t served any evolutionary purpose at all. It’s nothing more than the byproduct of the development of the male orgasm. The orgasm is to women, she believes, as nipples are to men.

勞埃德博士認爲，對女性性高潮的最佳解釋是，它並沒有任何進化上的意義，不過是男性性高潮的發展的副產品。她相信，性高潮之於女性就好比乳頭之於男性。

But now Dr. Pavlicev and her colleague, Günter P. Wagner of Yale University, are making the case that the human female orgasm has a deep evolutionary history that reaches back to early mammals.

不過，帕夫利塞夫博士與耶魯大學的京特•P•瓦格納(Günter P. Wagner)現在提出，人類女性的性高潮擁有可以追溯到原始哺乳動物的悠久進化史。

They began by getting better acquainted with the sex lives of other animals, poring through obscure old journals to gather information on species ranging from aardvarks to koalas.

他們首先更好地瞭解了其他動物的性行爲，從不知名的舊期刊裏梳理各物種的信息，範圍覆蓋了從非洲食蟻獸到考拉等各種動物。

They noted that many female mammals release oxytocin and prolactin during sex — the hormones released by women during orgasms. What’s more, in many of those species, females use a radically different kind of reproduction.

他們注意到，許多雌性哺乳動物會在性交過程中釋放催產素和催乳素，也就是人類女性高潮過程中釋放的荷爾蒙。此外，在這類物種裏，有不少物種的雌性採用與人類截然不同的繁衍方式。

While women release an egg each month, other female mammals, such as rabbits and camels, release an egg only after mating with a male.

人類女性每個月排一次卵，其他一些雌性哺乳動物則是與男性交配後纔會排卵，比如兔子和駱駝。

Ovulatory cycles evolved in only a few lineages of mammals, including our own, Dr. Pavlicev and Dr. Wagner found. Before then, our ancient mammal ancestors originally relied on ovulation triggered by sex with a male.

帕夫利塞夫博士與瓦格納博士發現，只有少數哺乳動物種羣進化出了排卵週期，包括我們人類。在那之前，我們古老的哺乳動物祖先起初是依賴與雄性交配來激發排卵的。

Those early mammals developed a clitoris inside the vagina. Only in mammals that evolved ovulatory cycles did the clitoris move away. Based on these findings, Dr. Pavlicev and Dr. Wagner argue that the female orgasm first evolved as a reflex to help females become pregnant.

這些原始哺乳動物身上出現了位於陰道內的陰蒂。只有進化出了排卵週期的哺乳動物，陰蒂才移去了別處。在這些發現的基礎上，帕夫利塞夫與瓦格納提出，人類女性性高潮起初進化出來，是作爲幫助女性懷孕的一種條件反射。

When early mammals mated, the clitoris could send signals to the brain, triggering hormones that released an egg. Once the egg became fertilized, the hormones may have helped ensure it became implanted in the uterus.

原始哺乳動物交配時，陰蒂可以向大腦發送信號，釋放出激發排卵的荷爾蒙。一旦卵子受精，這些荷爾蒙或許有助於保證它在子宮裏着牀。

This arrangement has worked well for mammals that rarely encounter males. It helps females make the most of each mating.

這種安排對於很少遇見雄性的哺乳動物來說是不錯的。它幫助雌性最大限度地利用每次交配的機會。

But eventually some mammals, including primates like us, started spending their lives in social groups. Females had access to regular sex with males, and orgasm as an ovulatory mechanism was no longer so useful. Our female forebears instead evolved a new system: releasing eggs in a regular cycle.

不過，後來有一部分哺乳動物，包括我們這樣的靈長目，開始以社羣的形式生活。雌性有了與雄性頻繁性交的機會，高潮作爲排卵機制的作用就不那麼重要了。我們的雌性祖先於是進化出了一種新機制：按照週期規律地排卵。

As the original purpose of the orgasm was lost, the clitoris moved away from its original position. Dr. Wagner speculated that this shift was part of evolution’s dismantling of a sensor system: “You don’t want to have the old signal sending noise at the wrong time,” he said.

隨着性高潮的初始意義喪失，陰蒂就離開了原來的位置。瓦格納猜測，這種移位相當於進化在廢除一個感官系統：“你不想要古老的信號系統在錯誤的時間發出噪音，”他說。

“Basically, we don’t know why this happened,” he added. But across mammalian species, “it’s just a very strong evolutionary pattern.”

“基本上，我們並不知道其中的原因，”他還說。不過在哺乳動物種羣中，“這的確是一種非常明顯的進化模式。”

Dr. Lloyd and Dr. Puts welcomed the new study as a provocative addition to the debate over the female orgasms.

勞埃德與普茨對這項新研究表示歡迎，認爲它加入了有關女性性高潮的辯論，能夠激發探討。

“I’m pretty excited that it’s being published,” Dr. Lloyd said, “because people are going to start talking about female orgasms and getting a fresh look at how much we don’t know about female orgasms, and thinking hard about what we need to know.”

“它的發表讓我很興奮，”勞埃德說，“因爲大家會開始談論女性的性高潮，重新審視我們在這方面有多麼大的認知空白，努力思考我們需要了解些什麼。”

The new theory may shed light on how the human female orgasm first evolved, but Dr. Pavlicev and Dr. Wagner said that it doesn’t settle the debate about its current role in women. “All directions are open,” Dr. Wagner said.

這項新理論或許有助於揭示人類女性性高潮起初如何進化而來，不過帕夫利塞夫與瓦格納表示，這並不能平息有關它對女性今時今日起到的作用的討論。“所有方向都有可能，”瓦格納說。

Dr. Wagner said that deciphering the history of the female orgasm might improve reproductive medicine.

瓦格納認爲，解開女性性高潮歷史的謎團，也許能推進生殖醫學的發展。

“I think you’re looking at the whole woman’s reproductive system a little differently when you have a model for how it might have evolved,” he said.

“我想，當你有了女性生殖系統可能怎樣進化而來的模型，就會對這整套系統有不太一樣的認識，”他說。