進化導(dǎo)致女性擇偶要求降低

譯/鄒夢蕓 審訂/趙剛

進化導(dǎo)致女性擇偶要求降低

譯/鄒夢蕓 審訂/趙剛

Evolution and Bad Boyfriends

Throughout history and in societies all over the world， parents have tried to in fl uence the love lives of their children—with mixed success1mixed success有成有敗。. Parents and children frequently don’t see eye to eye2see eye to eye意見一致。on what makes a suitable partner， as studies across cultures have con fi rmed.

[2] Whenever a pattern of human behavior is widespread， there is reason to suspect that it might have something to do with our evolutionary history.(Think of the fear of snakes， or the incest taboo.) You think your daughter’s boyfriend isn’t good enough? It may be evolution’s fault.

[3] But how could evolution have led to such an awkward situation as parent-child conflict over mates? In a recent paper in the journal Evolution and Human Behavior， we and two colleagues， the biologist Franjo Weissing and the social psychologist Bram Buunk， showed how it could work.

[4] When thinking about mate choice，the natural starting point is the theory of sexual selection. This theory， which focuses not on the struggle for existence but on the competition to attract sexual partners， has been hugely successful in explaining the diverse courtship behaviors and mating patterns in the animal kingdom， from the peacock’s flamboyant tail to the chirping calls of male crickets.

[5] Modern mathematical versions of this theory show how female mating preferences and male characteristics will evolve together. But when you try to apply the theory to humans， you hit a snag3hit a snag碰壁，遇到意外的困難。. In humans， there is an extra preference involved—that of the parents.

[6] At first sight， it might seem surprising that parents and their children should evolve to have any con fl ict at all.After all， they share many of the same genes， and both have an evolutionary interest in having those genes persist through the generations. Shouldn’t the preferences of parents and their children be perfectly aligned?

[7] Well， no—not completely. Parents each pass on half of their genes to each of their children， so from a genetic point of view， all children are equally valuable to them. It is in parents’evolutionary interests to distribute their resources—money， support， etc.— in such a way that leads to as many surviving grandchildren as possible，regardless of which of their children provide them.

[8] Children， by contrast， have a stronger genetic interest in their own reproduction than in that of their siblings， so each child should try to secure more than his or her fair share of parental resources. It is this con fl ict over parental resources that can lead to a con fl ict over mate choice.

[9] In our study， we built a computer model to simulate the evolutionary process. We generated a large virtual population4of males and females， the males all differing genetically in their ability to invest resources in raising children. The females had a genetically determined preference for5this male quality， which meant that females with a strong preference were more likely to end up with6a male who invested more.

[10] The males and females that paired up7in our model then mated and produced offspring， who inherited (with a small chance of mutation) the investing qualities and mating preferences of their parents. We ran our model over thousands of generations， observing which genetic traits thrived and which didn’t.

[11] Evolutionary biologists had built this kind of model before to understand mating preferences in other animals，but we added some new ingredients.First， we allowed a female’s parents to interfere with8interfere with干涉，干預(yù)。her choice of a male.Second， we allowed parents to distribute their resources among their children.

[12] We found that over time9over time隨著時間的推移。， parents in our model evolved to invest more resources in daughters who chose mates with few resources. This unequal investment was in the parents’ best interests， because a daughter with an unsupportive partner would pro fi t more from extra help than her more fortunate sisters (the principle of diminishing returns on investment). By helping their needier daughters， parents maximized their total number of surviving grandchildren.

[13] But this unequal investment created an incentive for daughters to “exploit”their parents’ generosity by choosing a partner who was less supportive. A daughter who was less picky than her sisters would accept a less helpful partner，but since her parents picked up the slack she ended up with a similar amount of support， while sparing herself the costs of holding out for the perfect man.

[14] As a result， the choosiness of females gradually declined over evolutionary time. To counterbalance this， the parental preference for caring sons-in-law increased. Hence the con fl ict.

[15] We’re not suggesting that the person you choose as a partner comes down entirely to your genes. Cultural factors， personal development and chance events presumably have a far greater influence. But given the prevalence of mate-choice conflict， it seems likely that evolution has played an important role. ■

縱觀人類歷史，不論在哪種社會中，父母都會試圖對子女的愛情生活施加影響，結(jié)果有成有敗。對于選擇什么樣的伴侶，父母與子女往往看法不一，跨文化研究已證實了這一點。

[2]只要人類的某種行為模式得以廣泛傳播，就有理由懷疑其可能與人類的進化史相關(guān)。（想想人類對蛇的恐懼或亂倫禁忌吧。）你對女兒的男友不夠滿意嗎？這可能得歸咎于進化。

[3]然而，進化是如何導(dǎo)致這種尷尬的呢？父母與子女為什么會就后者的擇偶問題發(fā)生沖突？最近，我們和兩位同事——生物學(xué)家弗拉尼奧·韋斯和社會心理學(xué)家布拉姆·布恩克——在《進化與人類行為》這本刊物上發(fā)表了一篇論文，對這一現(xiàn)象進行了分析。

[4]談到擇偶，自然要從性伙伴選擇理論開始。該理論研究的不是動物為生存而進行的斗爭，而是它們?yōu)槲曰锇槎归_的競爭，極為成功地解釋了動物界形形色色的求偶行為與交配模式，包括雄性孔雀華麗的尾巴以及雄性蟋蟀唧唧的鳴叫聲。

[5]性別選擇理論有多種現(xiàn)代數(shù)學(xué)版本，展示了雌性擇偶偏好與雄性特征如何共同進化，相互適應(yīng)。但若想將該理論應(yīng)用于人類，則會遇到意外的困難，因為人類擇偶還涉及另一個因素，那就是父母的偏好。

[6]乍看起來，經(jīng)過漫長的進化，父母與子女竟然還會存在沖突讓人驚訝。畢竟他們擁有許多相同基因，而且都希望這些基因能世世代代傳承下去。如此來看，父母與子女在后者擇偶問題上的偏好難道不該完美契合嗎？

[7]然而，事實并非如此，或并非完全如此。每個孩子都遺傳了父母各一半的基因。因此，從基因的視角來看，每個孩子對父母來說都同等重要。父母將其所擁有的資源（如金錢、援助等）以某種方式進行分配，以期子女們能夠生養(yǎng)眾多，從進化的角度而言，這符合父母的利益。父母并不在乎孩子是由哪個子女生養(yǎng)的。

[8]相較而言，從基因的角度來看，子女更關(guān)注的是其自身的繁衍，而非兄弟姐妹的繁衍，所以每個子女都會試圖從父母那里獲得更多的資源。正是這種在父母資源分配上的沖突，導(dǎo)致了父母和子女在擇偶問題上的分歧。

[9]本研究中，我們建立了一種計算機模型來模擬這一進化過程，生成了一個大型兩性實際種群。該種群中所有男性投入資源養(yǎng)育孩子的能力存在基因上的差異，而女性則在基因上極為偏好男性的這一能力，這就意味著這些女性更有可能選擇對養(yǎng)育孩子投入資源更多的男性。

[10]然后，模型中經(jīng)過配對的兩性進行交配并繁衍后代，后代則繼承了父母的資源投入與擇偶偏好的特征(基因突變的幾率很小)。我們使用該模型研究了成千上萬代的繁衍，觀察哪些基因特質(zhì)會健康發(fā)展，哪些會衰退。

[11]為了理解其他動物的擇偶偏好，進化生物學(xué)家早前已建立過這種模型，但我們此次增加了一些新的成分。首先，我們允許女方的父母對女兒的配偶選擇進行干預(yù)。其次，我們允許父母在子女間進行資源分配。

[12]研究發(fā)現(xiàn)，隨著時間的推移，模型中的父母會逐漸對配偶擁有的資源較少的女兒增加投入。這種不均等的投入對父母最為有利，因為與其他條件較好的姐妹相比，父母的額外投入會使得不到配偶支持的女兒獲益更多（這就是所謂的投資收益遞減原則）。通過幫助更為貧困的女兒，父母可使孫輩的存活數(shù)量達到最大化。

[13]但父母投資不均，會激勵女兒們選擇條件較差的配偶，以“利用”父母的慷慨投入。姐妹中不太挑剔的那個會接受資源較少的伴侶，但由于父母會給予更多幫助，她最終獲得了與其他姐妹相近的支持，而且還省去了選擇完美配偶的支出。

[14]結(jié)果，女性在進化過程中逐漸變得不再挑剔。為了達到平衡，父母則愈來愈偏好選擇對女兒更為體貼的女婿。沖突也因此而生。

[15]我們并不是說配偶選擇完全取決于基因。文化因素、個人發(fā)展及偶發(fā)事件等也許影響更大。但鑒于父母與子女擇偶沖突盛行，進化可能發(fā)揮了重要作用。 □

（譯者單位：華東師范大學(xué)翻譯系）

Most Famous Dogs in History (3)Canine Rescue Team, 9/11

Within 15 minutes of the attack on the World Trade Center on September 11， 2001， a trained search and rescue(SAR) dog named Appollo was onsite with his handler， Peter Davis of the New York City Police Department.In the following hours and days， over 350 SAR dogs and their handlers came to the Twin Towers site， and to the Pentagon， to search for survivors and to fi nd bodies.

“The SAR dogs worked with their handlers up to 16 grueling hours a day，” says Animal Planet， “and it became evident that the dogs were nearly as distraught as the human rescuers when there were so few survivors to be found. For the human rescue workers， the lack of survivors made the attacks feel ever more horrific and tragic. For the dogs trained to fi nd survivors， though， it felt like a personal failure.”