研究称生双胞胎只是幸运 不是因生育能力更强
近日，一项发表于《自然·通讯》（Nature Communications）杂志上的研究结果推翻了此前研究所认为的“双胞胎母亲有更强的生育能力”。
无注释原文：
Mothers of twins are not more fertile, just lucky
Science Daily
Are women who have twins more fertile? While previous studies concluded they are, a detailed analysis of more than 100,000 births from pre-industrial Europe by an international team of scientists shows they are not. The results of the study are now published in the scientific journal Nature Communications.
In humans, twinning usually occurs in about 1-3% of all births. Twinning is found in all populations despite being associated with a much higher risk of natal and postnatal health issues for both the mother and her children than single pregnancies. Given these risks, it seems that natural selection has prevented twinning from becoming more common during evolution. But why then has evolution by natural selection not prevented twinning altogether?
One common explanation has been that survival risks brought by twinning are partly hidden from natural selection because twinning comes with higher fertility. The idea is that women who are more fertile than average are also more likely to release more than one egg when they ovulate -- making twinning a marker of high fertility. Many studies analysed demographic data and obtained results consistent with this view.
However, this new study shows that the former analyses have been flawed. "Previous studies are problematic because they cannot tell us whether mothers with twins give birth more often because they are especially fertile, or because giving birth more often increases the chance that one of these births is to twins," explains principal investigator Alexandre Courtiol from the Leibniz Institute for Zoo and Wildlife Research in Germany.
The new results show that twinners are not unusually fertile. Previous science had mixed up cause and effect. "If a mother gives birth more often, it is more likely that one of these births is to twins -- just like you are more likely to win if you buy more lottery tickets, or to be in a car accident if you drive a lot," adds first author Ian Rickard from Durham University, UK. When the "lottery ticket effect" is taken into account, the authors found that mothers more likely to have twins actually gave birth less often -- a result that contradicts previous findings.
To re-examine the relationship between twinning and fertility, the international team of 14 scientists combined large datasets of birth outcomes from several parts of pre-industrial Europe (today's Finland, Sweden, Norway, Germany and Switzerland). "All these data originate from old parish records that have been meticulously digitised and transcribed," explains co-author Virpi Lummaa from University of Turku, Finland. "To avoid the statistical trap that plagued former studies, we also had to deploy efficient and carefully calibrated statistical procedures," adds co-author François Rousset from the Institut des Sciences de l'Evolution in Montpellier, France.
Figuring out what shapes the relationship between twinning and fertility is not only a question of academic interest but also a matter of public health. Indeed, biomedical studies looking for ways to improve female fertility have compared mothers with and without twins. However, co-author Erik Postma from the University of Exeter in the UK points out that, "such study designs ignore the multitude of factors influencing how often a woman gives birth, which will mask any genuine differences in physiology between mothers with and without twins." In short, comparing groups of mothers with twins to groups of mothers without may hide the effects of twinning and fertility genes where they exist, or create the illusion of these if they do not exist.
"There is still much we do not understand about twinning, but our study suggests that twinning has not been eliminated by natural selection for two reasons. First, twinning is a consequence of double ovulation, which compensates for reproductive ageing and benefits all but the youngest of mothers. Second, when the risk of early mortality of twins is not too high, twinning is associated with larger family sizes although women with twins give birth less often. This is because twin births bring two offspring rather than one," concludes Courtiol.
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注：中文文本为机器翻译仅供参考，并非一一对应
含注释全文：
Mothers of twins are not more fertile, just lucky
Science Daily
Are women who have twins more fertile? While previous studies concluded they are, a detailed analysis of more than 100,000 births from pre-industrial Europe by an international team of scientists shows they are not. The results of the study are now published in the scientific journal Nature Communications.
拥有双胞胎的女性是否更有生育能力？虽然以前的研究认为她们会，但一个国际科研团队对工业化前欧洲的10万多个新生儿的详细分析表明并非如此。这项研究的结果现在发表在科学杂志《自然·通讯》（Nature Communications）上。
fertile
fertile /ˈfɜː.taɪl/ 1）表示“肥沃的；富饶的”，英文解释为“Fertile land can produce a large number of good quality crops.”
2）表示“（动物或植物）可繁殖的，能生育的，能结果的”，英文解释为“Fertile animals or plants are able to produce (a lot of) young or fruit.”举个🌰：People get less fertile as they get older. 随着年龄增长，人的生育能力逐渐下降。
In humans, twinning usually occurs in about 1-3% of all births. Twinning is found in all populations despite being associated with a much higher risk of natal and postnatal health issues for both the mother and her children than single pregnancies. Given these risks, it seems that natural selection has prevented twinning from becoming more common during evolution. But why then has evolution by natural selection not prevented twinning altogether?
在人类中，双胞胎通常发生在大约1-3%的所有新生儿中。尽管与单胎妊娠相比，双胞胎对母亲及其孩子的出生和产后健康问题的风险要高得多，但在各种人群中都有双胞胎。鉴于这些风险，自然选择似乎阻止了让双胞胎在进化过程中变得更加普遍。但是，为什么自然选择的进化没有完全阻止双胞胎的出现呢？
natal
natal /ˈneɪ.təl/ 表示“（人或动物）出生的”，英文解释为“relating to where a person or animal was born”如：her natal village/city/home 她的出生地/城市/家乡。
postnatal
表示“分娩后的，产后的”，英文解释为“relating to the period of time immediately after a baby has been born”如：postnatal care 产后护理。
补充：
📍pre-natal，prenatal表示“产前的”（Prenatal is used to describe things relating to the medical care of women during pregnancy.）
One common explanation has been that survival risks brought by twinning are partly hidden from natural selection because twinning comes with higher fertility. The idea is that women who are more fertile than average are also more likely to release more than one egg when they ovulate -- making twinning a marker of high fertility. Many studies analysed demographic data and obtained results consistent with this view.
一种常见的解释是，双胞胎带来的生存风险部分地被自然选择所掩盖，因为双胞胎伴随着更高的生育率。这种观点认为，比一般人更有生育能力的女性在排卵时也更有可能排出一个以上的卵子--使双胞胎成为高生育率的标志。许多研究分析了人口统计学数据，并获得了与这种观点一致的结果。
ovulate
ovulate /ˈɒv.jə.leɪt/ 表示“（女性或雌性动物）排卵，产卵”，英文解释为“(of a woman or female animal) to produce an egg from which a baby can be formed”举个🌰：
Some women take drugs to help them ovulate.
有些妇女服药来帮助排卵。
demographic
1）作形容词，表示“人口的；人口统计的；人口学的”，英文解释为“relating to demography (= the study of populations and the different groups that make them up)”举个🌰：
There have been monumental social and demographic changes in the country.
该国的社会和人口状况已经发生了巨大的变化。
2）作名词，表示“（顾客）族群”，英文解释为“a group of people, for example customers, who are similar in age, social class, etc.”举个🌰：
This demographic (young teenagers) is the fastest-growing age group using the site.
该族群（十几岁的年轻人）是使用这个网站人数增长最快的年龄群体。
However, this new study shows that the former analyses have been flawed. "Previous studies are problematic because they cannot tell us whether mothers with twins give birth more often because they are especially fertile, or because giving birth more often increases the chance that one of these births is to twins," explains principal investigator Alexandre Courtiol from the Leibniz Institute for Zoo and Wildlife Research in Germany.
然而，这项新的研究表明，以前的分析是有缺陷的。来自德国莱布尼茨动物园和野生动物研究所的首席研究人员亚历山大·库蒂奥尔（Alexandre Courtiol）解释说：“以前的研究是有问题的，因为它们不能告诉我们有双胞胎的母亲更频繁地生育是因为她们特别能生，还是因为更频繁地生育增加了这些生育中是双胞胎的可能性。”
The new results show that twinners are not unusually fertile. Previous science had mixed up cause and effect. "If a mother gives birth more often, it is more likely that one of these births is to twins -- just like you are more likely to win if you buy more lottery tickets, or to be in a car accident if you drive a lot," adds first author Ian Rickard from Durham University, UK. When the "lottery ticket effect" is taken into account, the authors found that mothers more likely to have twins actually gave birth less often -- a result that contradicts previous findings.
新的结果显示，生双胞胎的人生育能力并非特别强。以前的科学将因果关系（cause and effect）混为一谈。第一作者英国杜伦大学（Durham University）的伊恩·里卡德（Ian Rickard）补充说：“如果一个母亲更频繁地生育，那么这些生育中的一个更有可能是双胞胎--就像你买更多的彩票就更有可能中奖，或者如果经常开车就更有可能发生车祸。”当考虑到“彩票效应”时，作者发现，更有可能生双胞胎的母亲实际上更少生育--这一结果与以前的研究结果相矛盾。
contradict
1）表示“相抵触；相矛盾；相反”，英文解释为“to be so different from each other that one of them must be wrong”举个🌰：
The two stories contradict each other.
这两种说法相互抵触。
2）表示“反驳；驳斥；批驳”，英文解释为“to say that sth that sb else has said is wrong, and that the opposite is true”举个🌰：
All evening her husband contradicted everything she said.
整个晚上她说什么丈夫都反驳。
To re-examine the relationship between twinning and fertility, the international team of 14 scientists combined large datasets of birth outcomes from several parts of pre-industrial Europe (today's Finland, Sweden, Norway, Germany and Switzerland). "All these data originate from old parish records that have been meticulously digitised and transcribed," explains co-author Virpi Lummaa from University of Turku, Finland. "To avoid the statistical trap that plagued former studies, we also had to deploy efficient and carefully calibrated statistical procedures," adds co-author François Rousset from the Institut des Sciences de l'Evolution in Montpellier, France.
为了重新审视双胞胎和生育率之间的关系，这个由14名科学家组成的国际团队结合了来自工业化前欧洲几个地区（如今的芬兰、瑞典、挪威、德国和瑞士）的大规模出生结果数据集。“所有这些数据都来自于古老的教区记录，这些记录已被精心数字化和转录，”共同作者芬兰图尔库大学（University of Turku）的维尔皮·卢马（Virpi Lummaa）解释说。“为了避免困扰以前研究的统计陷阱，我们还必须利用高效和仔细校准的统计程序，”来自法国蒙彼利埃（Montpellier）进化科学研究所（the Institut des Sciences de l'Evolution）的共同作者弗朗索瓦·鲁塞（François Rousset）补充说。
originate
表示“起源，发源，发端；产生”，英文解释为“to come from a particular place, time, situation, etc.”举个🌰：
Although the technology originated in the UK, it has been developed in the US.
尽管这项技术起源于英国，但它在美国得到了发展。
parish
parish /ˈpær.ɪʃ/ 表示“（某些基督教会中主教管区下有自己教堂的）堂区，教区；行政堂区（英格兰的基层行政单位）”，英文解释为“in some Christian denominations, an area cared for by one priest with its own church, or (in England) the smallest unit of local government”如：the parish church/magazine/priest/register 堂区教堂/杂志/神父/登记簿。
meticulously
meticulously /məˈtɪk.jə.ləs.li/ 表示“细致地；一丝不苟地；拘泥地”，英文解释为“in a way that shows great care and attention to detail”。
transcribe
表示“转录（为另一种书写形式）”，英文解释为“to change a piece of writing or music into another form, for example into a different writing system or into music for different instruments”。
plague
1）作名词可表示“瘟疫，疫病”，如：a fresh outbreak of plague 瘟疫的新一轮爆发；
2）作动词表示“不断困扰，折磨，使苦恼”，英文解释为“to cause pain, suffering, or trouble to someone, especially for a long period of time”，举个🌰 ：
She was plagued by weakness, fatigue, and dizziness.
她受虚弱、疲劳和眩晕所折磨。
🎬电影《白宫管家》（The Butler）中的台词提到：It's time we take a stand against these injustices that have plagued our community. 现在是时候该表明立场和采取行动来对抗这些已困扰我们很久了的不公。
deploy
1) 表示“利用，调动（尤指想法、论据等）；有效运用；发挥…的作用”，英文解释为“to use something for a particular purpose, especially ideas, arguments etc”，如：a job in which a variety of professional skills will be deployed 要用到多项专业技术的工作。
2) 表示“部署，调度（士兵、军事装备等）”，英文解释为“to organize or move soldiers, military equipment etc so that they are in the right place and ready to be used”，如：deploy forces/troops/weapons etc，NATO's decision to deploy cruise missiles 北约要部署巡航导弹的决定。
calibrate
表示“标定，校准（刻度，以使测量准确）”，英文解释为“to mark units of measurement on an instrument such as a thermometer so that it can be used for measuring sth accurately”。
Figuring out what shapes the relationship between twinning and fertility is not only a question of academic interest but also a matter of public health. Indeed, biomedical studies looking for ways to improve female fertility have compared mothers with and without twins. However, co-author Erik Postma from the University of Exeter in the UK points out that, "such study designs ignore the multitude of factors influencing how often a woman gives birth, which will mask any genuine differences in physiology between mothers with and without twins." In short, comparing groups of mothers with twins to groups of mothers without may hide the effects of twinning and fertility genes where they exist, or create the illusion of these if they do not exist.
弄清楚是什么形成了双胞胎和生育率之间的关系，不仅是一个学术兴趣问题，也是一个公共卫生问题。事实上，寻求改善女性生育能力的生物医学研究已对有双胞胎和无双胞胎的母亲进行了比较。然而，来自英国埃克塞特大学（the University of Exeter）的共同作者埃里克·波斯特马（Erik Postma）指出，“这种研究设计忽略了影响女性生育频率的众多因素，掩盖了有双胞胎和无双胞胎母亲之间任何真正的生理差异。”简而言之，将有双胞胎的母亲群体与没有双胞胎的母亲群体进行比较，可能会掩盖存在双胞胎和生育基因的影响，或者在不存在这些影响的情况下造成假象。
multitude
表示“大量，许多，中多”，英文解释为“A multitude of things or people is a very large number of them.”举个🌰：
There are a multitude of small, quiet roads to cycle along.
有多条可以骑自行车的僻静小路。
illusion
表示“错误的观念；幻想；假象，错觉”，英文解释为“a false idea or belief, especially about sb or about a situation”举个🌰：
I have no illusions about her feelings for me.
我对她跟我的感情不抱什么幻想。
"There is still much we do not understand about twinning, but our study suggests that twinning has not been eliminated by natural selection for two reasons. First, twinning is a consequence of double ovulation, which compensates for reproductive ageing and benefits all but the youngest of mothers. Second, when the risk of early mortality of twins is not too high, twinning is associated with larger family sizes although women with twins give birth less often. This is because twin births bring two offspring rather than one," concludes Courtiol.
“我们对双胞胎还有很多不了解，但我们的研究表明，双胞胎并没有被自然选择所淘汰，原因有二：首先，双胞胎是双排卵的结果，弥补了生育年龄老化的缺陷，除了最年轻的母亲外，所有母亲都能从中受益。第二，当双胞胎的早期死亡风险不是太高时，双胞胎与较大的家庭规模有关——尽管有双胞胎的女性生育的频率较低。这是因为双胞胎的出生带来了两个而不是一个后代，”库蒂奥尔总结道。
eliminate
表示“排除；消除；清除”，英文解释为“to remove or take away someone or something”举个🌰：
A move towards healthy eating could help eliminate heart disease.
养成健康的饮食习惯有助于消除心脏病诱因。
compensate
表示“弥补，补偿”，英文解释为“to provide something good or useful in place of something or to make someone feel better about something that has failed or been lost or missed”举个🌰：
Nothing will ever compensate for his lost childhood.
什么也不能弥补他失去的童年。
reproductive
表示“生殖；生育；繁殖”，英文解释为“relating to the process of reproduction”。
mortality
mortality /mɔːˈtælɪtɪ/ 表示“死亡数量；死亡率”，英文解释为“the number of deaths in a particular situation or period of time”。
区分：
📍morbidity /mɔːˈbɪdɪtɪ/ 表示“发病（率）”，英文解释为“the morbidity of a disease is how many people have it in a particular population”。
offspring
表示“（人的）后代，子女，子嗣”，英文解释为“a person's children”举个🌰：
His sister came over on Saturday with all her offspring.
他的姐姐星期六带着她的一大群子女过来串门。
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