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When you get "The Talk" as a kid and learn about the birds and the bees, the information you get doesn't have a timestamp.
我们小时候有学过初步的性教育，而我们所了解的信息中是没有时间戳的。
Unlike lots of other animals, there's no such thing as the "mating season" for humans:
和其他的多数动物不同，人类没有所谓的“繁殖季节”。
People can get together and make babies at any time of year. And cleary, they do.
人类可以随时繁育下一代，而且人类也确实如此。
From what we can tell, the reason humans don't have a mating season has to do with why other animals do.
就我们所知，人类没有繁殖季节的原因和其他动物为什么有繁殖季节相关联。
And a lot of it might involve how we raise our young.
大部分原因或许是由于人类养育下一代的方式不同。
Plenty of animals — like horses, some types of birds, goats, sheep, and other critters have mating seasons.
大部分动物，比如马、一些鸟类、山羊、绵羊和其他小生物都有繁殖季节。
Appropriately, they're called seasonal breeders.
它们被称为季节性繁殖家畜。
The members of those species only go through certain hormonal cycles during a portion of the year.
那些种类的动物只有在一年的某一段时间内才有荷尔蒙分泌周期。
They lead to females releasing eggs, often physical changes in males, and behavioral changes that promote sexual activity.
荷尔蒙分泌周期致使雌性产卵，通常会也导致雄性的一些生理变化以及行为变化，促进它们的性行为。
This strategy evolved to make sure that, when offspring are born,
这种策略得到了进化以确保下一代出生时，
they arrive during a time of year when the environment is friendlier and there's food available.
它们有更友好的环境且食物充足。
For example, many birds in the Arctic Circle start laying their eggs in May,
例如，北极圈内的很多鸟类在五月开始产卵，
so that the chicks are born in June and July, when prey is abundant.
这样一来，小鸟就会在六月和七月产生，那时的猎物很充足。
The start and end of these seasons are triggered by changes in the environment.
繁殖季节的开始和结束是由环境的变化所引起的。
For example, animals' biological clocks might note the days getting longer, which is a sign of the arrival of spring.
例如，动物的生物钟会注意到白天时间变长，这就预示着春天的到来。
And that might spur the physiological changes necessary for procreation.
这还会刺激生育的必要生理变化。
The human reproductive cycle, on the other hand, isn't tied to a yearly clock.
而另一方面，人类的生殖周期和年度生物钟并不关联。
Like many other primates, we're called continuous breeders, and we're capable of producing offspring during any season.
和其他许多灵长类动物一样，我们被称为连续生殖者，并且我们可以在任何季节繁育后代。
Admittedly, people aren't equally fertile every day.
不可否认的是，个体的繁育能力有所差异。
Roughly every month, there's a window where an egg is optimally positioned to be fertilized.
基本每个月都会有一个卵子处于最佳受精位置。
But that still happens on predictable, 28-day intervals throughout the whole year.
但是这时间也是可预测的，全年每28天一次。
Regardless, the evolutionary reasons for this aren't quite clear.
不论如何，其进化的原因尚不明确。
It may just be that the environmental risks to our offspring aren't as significant.
这或许是因为人类后代的环境风险并没有那么显著。
Humans and other primates devote a lot of energy to caring for new babies,
人类和其他灵长类动物对下一代的照顾都投入了很多精力，
so those babies aren't left to find their own food, or out vulnerable to the elements.
因此，那些新生宝宝不用自己找食物，不会受敌人威胁。
But it's hard to know for sure if this is the right explanation.
但是难以确切知晓这是否是正确的解释。
Of course, even without a mating season, there are still times during the year when people are more likely to have kids.
当然，即使是没有繁育季节，在一年中的某些时候，人类更有可能繁育下一代。
Birth rates in the United States, at least, are highest in the summer and fall,
至少美国的出生率在夏季和秋季最高，
suggesting that people are having more sex and conceiving more babies during the winter.
这表明人类在冬季会有更多性行为并怀上小宝宝。
That might be because, at least in many regions, the cold drives people indoors where there's not as much to do.
这或许是因为，至少在很多地区，寒冷会让认更想待在室内，而室内也没事可干的。
It could also be because of sperm viability.
这也或许是由于精子活力。
A 2013 study in the American Journal of Obstetrics and Gynecology found that,
《美国产科与妇科学杂志》上的一项2013年的研究发现
in more than 6000 samples, average sperm quality was highest during the winter,
在六千多个样本中，平均精子质量在冬季最高，
when the cells are less likely to be damaged by heat.
那时细胞不易受炎热损伤。
But babies are still conceived during warmer months and in warmer climates in general.
但是通常还是在更加温暖的季节和气候时怀上宝宝。
Still, if you live in the United States and your birthday is in August, you are definitely not alone.
如果你住在美国并且你的生日是在8月，那么你绝对不是一个人。
It's just not because of a mating season. Thanks for watching this episode of SciShow which is a Complexly production!
只是这并不是由于繁殖季节。感谢收看本期《科学秀》，本期视频由Complexly制作出品！
Even if humans don't have a mating season, there's still a lot to learn about sex in general.
人类即使没有繁殖季节，关于性还是有很多知识可以学习的。
And that's where one of our sister channels, Sexplanations, comes in! You can check it out at youtube.com/sexplanations.
此处欢迎我们的姊妹频道Sexplanations出场！你可以点击登录youtube.com/sexplanations，进行观看。
