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达尔文家族与近亲繁殖

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查尔斯 • 达尔文关于遗传、适应和进化的研究中,有很多实验研究了杂交和近亲繁殖在植物和动物中的影响,这样的近亲配对往往会产生更虚弱、更多病的后代。
Charles Darwin's studies of heredity, adaptation and evolution included many experiments into the effects of crossbreeding and inbreeding in both plants and animals. Such consanguineous pairing often resulted in weaker, more sickly descendants.
具有讽刺意味的是,达尔文自己的血统和婚姻也可以拿来做实验。在29岁的时候,他和他的第一代表妹,也就是他舅舅的女儿Emma Wedgwood订婚了。达尔文意识到近亲结婚的危险,并且怀疑过自己和妻子相近的基因关系是不是对他们的孩子的健康造成了不良影响,他们的(10个中的)三个孩子在11岁之前就死去了。在写给一位友人的信中,达尔文提到了他对孩子们的担忧,写到“他们不是很有活力。”
Ironically, his own lineage and marriage could have been experiments as well. At the age of 29, he proposed to his first cousin, Emma Wedgwood, the daughter of his mother's brother. Darwin realized the dangers of inbreeding and wondered if his close genetic relation to his wife had had an ill impact on his children's health, three (of 10) of whom died before the age of 11. In a letter to friend, Darwin noted his concern for his children, writing that "they are not very robust."
达尔文和他表妹的婚姻并不是这两个血缘唯一一次结合,事实上Darwin-Wedgwood家族有很多例近亲配对。《生物科学》于5月3日在线出版杂志中有一篇新分析,它显示达尔文对后代健康的一些担忧有可能是正确的。
Darwin's marriage to his cousin was not the only mixing of blood in the two lines. The Darwin-Wedgwood family in fact had several instances of close family matches, and a new analysis, published online May 3 in the journal BioScience, shows that some of Darwin's concerns about his offspring's health might have been valid.
分析工作由位于Mansfield的俄亥俄州立大学进化、生态和有机生物部门的荣誉退休教授Tim Berra主持,分析发现达尔文的孩子们的确受“中等程度近亲繁殖的影响”,并且在家族的儿童中“儿童死亡率和近亲繁殖有显著的、确定的联系。”
The analysis, led by Tim Berra, professor emeritus in the Department of Evolution, Ecology and Organismal Biology at the Ohio State University in Mansfield, found that Darwin's kids did have "a moderate level of inbreeding" and in the family's children, there was "a significant positive association between child mortality and inbreeding."
当两个个体交配时,父母双方的基因物质都会被遗传给下一代。所以就算其中一个家长携带着一个有害的隐形特征,另外一个家长很可能有一个该特征的健康版本,这个健康的特征会在后代中显现出来。然而,假如两位家长都携带有一个隐形等位基因,那么这会增加他们的孩子只有恶性基因的几率,而像近亲一样有很多共同的基因物质时这种情况更可能发生。
When two individuals mate, genetic material from both parents is passed on to the progeny. So even if one parent carries a harmful recessive trait, the other parent is likely to have a healthier version, which will manifest itself in the offspring. If both parents, however, carry a recessive allele—which is more likely to happen if they share much of their genetic material, as close relatives do—then they raise the chances that their child will have only the bad genes.
Berra和他的同事们对于达尔文和Wedgwood家族四代中的25个核心家庭的研究发现,家族中儿童死亡率比当时总体人口总的儿童死亡率低一些。但是在那些存在高度近亲繁殖的核心家庭中,后代健康的几率估计下降了5.4%。而查尔斯 • 达尔文孩子中的常染色体很可能超过6%都是相同的(也就是说是纯合子),这个数字大约是第二代表亲的孩子中相同基因数的四倍。
Berra and his colleagues' assessment of 25 nuclear families across four generations of Darwins and Wedgwoods found a slightly lower-than-average child mortality rate compared with the general population of the time. But in those nuclear families with higher levels of inbreeding, offspring had an estimated 5.4 percent reduction in fitness. And the autosomal genomes of Charles Darwin's children were likely more than 6 percent identical (that is, homozygous). That number represents about four times the amount of overlap than children of second cousins would be expected to have.
Berra和他的同事们提出,虽然达尔文的孩子中没有任何明显记录在案的身体或心理上的畸形,那三个死去的孩子却是由于传染性疾病死亡的,而高度近亲繁殖的后代更容易染上这样的病。一个孩子在出生23天后死亡,另外一个生长不正常的在18个月时死去了。第三个很可能是由于肺结核死去的,而近亲繁殖会加大后代染上肺结核的风险。
Although none of Darwin's children had obvious documented physical or mental deformities, the three who died appear to have suffered from infectious disease, which is more likely to be contracted in those with higher levels of inbreeding, Berra and his colleagues noted. One died at 23 days old, and another, who was not developing normally, died at 18 months. The third likely died of tuberculosis, for which inbreeding increases the contraction risk.
很多有名声且势力强大的家族都因与近亲结婚而著名,比如Hapsburgs家族和一些古代埃及法老。在历史上当生活团体更小更孤立的时候,和远亲或近亲结婚都是很普遍的做法。但是在达尔文的时代已经有“近亲结婚会导致耳聋、哑巴和眼瞎等等”的说法,达尔文于1870年在一封写给国会议员John Lubbock的信中写到。达尔文当时希望政府能够收集广大人口关于表亲结婚频率和他们后代健康状况的数据,他还要求有关近亲结婚影响的问题被收录到英国人口普查工作中。
Many famous and powerful families have been renowned for their pairing of close relatives, including the Hapsburgs and some ancient Egyptian pharaohs, and marrying relatives—both close and distant—was in general more common historically when groups were smaller and more isolated. But by Darwin's time it was already assumed that "consanguineous marriages lead to deafness & dumbness, blindness [etc.]," Darwin wrote in a letter to parliamentarian John Lubbock in 1870. Darwin had been hoping the government could accumulate broad population-based data about the frequency of cousins marrying and the health of their offspring, and he requested questions to this effect be included in England's census.
达尔文的要求被拒绝了,但是他的担忧如今仍存在,美国超过一半的州都对第一代表亲结婚进行了明确的限制。
Darwin's request was denied, but his concern lives on today. More than half of the states in the U.S. have explicit limits on first-cousin marriages.
标签:达尔文 家族
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2010-05-05 19:45 编辑:kuaileyingyu
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  • Guest 说:

    My grandparents who are close relative,cousin actually.they gave birth to 10 kids,only 2 of them survived.I heard one couple who are cousin two,their first kid looks like meat ball without arms and legs,and died immediately.horror

    2010-05-07 11:26 回复 支持(0) 反对(0) 沙发
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