经济学人下载:动物性取向—本能(1)

When it comes to sexual behaviour, the animal kingdom is a broad church.
说到性行为，动物王国是一个广教派。

Its members indulge in a wide variety of activities, including with creatures of the same sex.
其成员沉迷于各种各样的活动，包括与同性动物。

Flying foxes gather in all-male clusters to lick each other's erect penises.
雄性飞狐聚集在一起相互舔对方勃起的阴茎。

Male Humboldt squid have been found with sperm-containing sacs implanted in and around their sexual organs in similar quantities to female squid.
人们发现雄性洪堡鱿鱼的性器官内和周围都植入了含有精子的囊，其数量与雌性鱿鱼相当。

Female snow macaques often pair off to form temporary sexual relationships that includes mounting and pelvic thrusting.
雌性雪猴经常结对形成临时的性关系，包括骑乘和骨盆抽动。

Same-sex sexual behaviour has been recorded in some 1,500 animal species.
记录中已有1500种动物有同性性行为。

The mainstream explanations in evolutionary biology for these behaviours are many and varied.
进化生物学对这些行为的主流解释是多种多样的。

Yet they all contain a common assumption: that sexual behaviours involving members of the same sex are a paradox that does indeed need explaining.
但它们中都有一种共同的假设：同性性行为是一个确实需要解释的悖论

Reproduction requires mating with a creature of the opposite sex, so why does same-sex mating happen at all?
繁殖需要和异性交配，那么为什么会出现同性伴侣呢？

A paper just published in Nature Ecology and Evolution offers a different approach.
刚刚发表于《Nature Ecology and Evolution 》的一篇论文提供一种不同的方法。

Instead of regarding same-sex behaviour as an evolutionary oddity emerging from a normal baseline of different-sex behaviour,
作者们并没有将同性行为看做是一种与异性行为正常基线相反的、进化中的反常现象，

the authors suggest that it has been a norm since the first animals came into being.
而是认为这是自第一只动物出现以来的一种常态。

The common ancestor of all animals alive today, humans included, did not, they posit,
他们假设，今天所有动物的共同祖先，包括人类，

have the biological equipment needed to discern the sex of others of its species.
没有必要的生物设备来辨别其他物种的性别。

Rather, it would have exhibited indiscriminate sexual behaviour—and this would have been good enough to transmit its genes to the next generation.
相反，它会显示出任意的性行—并且这将足以把它的基因传给下一代。

The group of young researchers from institutions across America who wrote the paper, led by Julia Monk, a graduate student at Yale,
来自美国各机构的年轻研究员组成团队写了一篇论文，该论文由耶鲁大学研究生Julia Monk领头，

argue that conventional models of sexual behaviour's evolution take two things for granted that they should not.
他们认为传统的性行为进化模型将两件事看成是理所当然的，但其实并不应该如此。

The first is that the cost of same-sex behaviour is high because energy and time spent engaged in it do not contribute to reproductive success.
第一件事是，同性行为成本更高，因为花在这上边的精力和时间无助于成功的繁殖。

If that were true it would indeed mean that maintenance of same-sex behaviour over the generations
如果这是真的，那么这确实意味着同性行为在几代人之间得以维持

requires some exotic explanation whereby such activity confers benefits that outweigh the disadvantage.
是需要一些奇特的解释，这种行为利大于弊。

The second assumption is that same-sex activity evolved separately in every species that exhibits it,
第二个假设是，同性性行为在每一个物种中都是独立进化的，

from an ancestral population that engaged exclusively in different-sex behaviour.
从一个只专注异性性行为的祖先群体中演变而来。