今天精选gre阅读背景材料内容是双胞胎的家庭对于宝宝、妈妈、家庭的益处。
Mothers of twins do not just get twice the bundle of joy—they are also healthier than other mothers
拥有双胞胎的母亲不仅能得到双份的快乐，而且她们会比其她母亲更健康。
THROUGHOUT history, twins have provoked mixed feelings. Sometimes they were seen as a curse—an unwanted burden on a family’s resources. Sometimes they were viewed as a blessing, or even as a sign of their father’s superior virility. But if Shannen Robson and Ken Smith, of the University of Utah, are right, twins have more to do with their mother’s sturdy constitution than their father’s sexual power.
在历史上，对待双胞胎有着复杂的感情。有时，他们被视为祸根--家庭中不受欢迎的负担。有时，他们被视为祝福，或作为他们父亲拥有更好的性能力的一个标志。但如果犹他大学的夏侬.罗布森和肯.史密斯是正确的，那么双胞胎为他们的母亲那健壮的体格所做的比为他们的父亲的性能力方面所做的更多。
At first blush, this sounds an odd idea. After all, bearing and raising twins is taxing, both for the mother and for the children. Any gains from having more than one offspring at a time might be expected to be like higher infant and maternal mortality rates. On this view, twins are probably an accidental by-product of a natural insurance policy against the risk of losing an embryo early in gestation. That would explain why many more twins are conceived than born, and why those born are so rare (though more common these days, with the rise of IVF). They account for between six and 40 live births per 1,000, depending on where the mother lives.
乍看之下，这好像听起来好像是一个奇怪的想法，毕竟对于母亲和孩子，生产和抚养双胞胎是很费力的。每次从多于一个孩子那里获得的比期望的更多，通常会伴随着较高的婴儿死亡率和母亲死亡率。根据这种观点，双胞胎很可能是一次在怀孕期间用自然保障方式防止流产的意外的副产品。这样就能解释为何双胞胎怀的比生的多，而且为什么生的会这么少(虽然现在更多的运用试管受精已经很平常)。他们解释说每1000个中成活率在6到40之间，这要根据母亲生活的地方。
Dr Robson and Dr Smith, however, think that this account has got things the wrong way round. Although all women face a trade-off between the resources their bodies allocate to reproduction and those reserved for the maintenance of health, robust women can afford more of both than frail ones. And what surer way to signal robustness than by bearing more than one child at a time? In other words, the two researchers conjectured, the mothers of twins will not only display greater overall reproductive success, they will also be healthier than those who give birth only to singletons.
然而，罗布森博士和史密斯博士认为这个解释是事情处于错误中。尽管许多女人面临着一个权衡，那就是在身体分配给生育所需的资源和保留给保持身体健康所需营养之间权衡。强健的母亲可能比瘦弱的母亲提供的更多。而且能有什么比健壮的母亲生育多于一个孩子更有说服力呢?换言之，这两位调查者推测，双胞胎的母亲不仅更好的展示了整体的生育成功，也会比只生一个孩子的母亲更健康。
Alas, pinning down evolved relationships between fertility and health is tricky. Modern medicine and the pampering effects of economic growth mean that, these days, women everywhere give birth to fewer children than they did in the distant evolutionary past, when human bodies and physiology were forged—even as more of the offspring they do bear survive into adulthood. In Europe and North America this demographic transition began in earnest around 1870.
唉，控制生育和保持健康之间的关系是很难的。现代医学和经济的发展精心呵护的结果是，当人体和生理机能被伪造，这个时候的女性无论在哪里都会比处在以前缓慢发展时期的女性生的孩子要少，因为她们生的孩子大部分能活到成年。在欧洲和北美这个人口过渡开始于1870年左右。
One way round this is to look at records gathered before the demographic transition began. The problem is that few authorities then kept tabs diligently enough to provide adequate fodder for statistical analysis. One exception was Utah, a state largely settled in its early days by Mormons, who have always taken such matters seriously. As a result, Utah’s Pedigree and Population Resource, a database of which Dr Smith is the director, contains 1.6m genealogical records for people in the state from the early 1800s to the 1970s.
围绕着寻找记录及合并的方法要在人口过渡开始前完成。这个问题是只有很少的当局会勤奋的为统计分析提供足够的材料保持制表符。一个例外是犹他州，在早期有摩门教徒定居在此，他们总是严肃的对待事情。结果，在史密斯博士作为主管的一个数据库中，犹他州的血统和人口资源包括160万份在早期的1800世纪到 1970世纪中居住于此的居民的家谱记录。
To test their theory that the bearers of twins are supermums, Dr Robson and Dr Smith scoured the records for women born between 1807 and 1899 who survived past the age of 50, when the menopause typically strikes. They excluded those married more than once, those widowed before they were 50 and also (this being Utah) those wives who were part of one of the polygamous marriages once legal among the state’s Mormon settlers. (In a study published earlier this year, Dr Smith and his colleagues found that the more wives a Mormon woman had to compete with for her husband’s attentions, the fewer children she was likely to produce.) This left them with some 59,000 women, around 4,600 of whom had given birth to twins at least once.
为了检验他们关于双胞胎母亲是超级妈妈的说法罗伯森博士和史密斯博士搜集了关于超过50岁的更年期正常来临并在1807年到1899年进行生产的妇女的资料。她们只结过一次婚，在50岁以前就守寡并且这些妻子是一夫多妻制婚姻的一部分，而这在这一地区的摩门教徒中是合法的。(今年早期发布的一项研究表明，史密斯博士和他的同事发现在众多妻子中，一个摩门妇女不得不为了吸引丈夫的关注而竞争，这样她很可能会生更少的孩子。)这样的妇女大约有59000名，其中4600名至少一次的生产双胞胎。
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