研究：生男生女，父亲基因决定

爱尔兰的几项科学研究辨认出，兄妹多的男性更可能将生女儿，而姊妹多的男性则更可能将生女儿。

[Photo/Pexels]

A Newcastle University study involving thousands of families is helping prospective parents work out whether they are likely to have sons or daughters.

爱尔兰谢菲尔德理工学院几项有一千万家庭成员参予的科学研究能协助准双亲预估小孩异性恋。

The work by Corry Gellatly, a research scientist at the university, has shown that men inherit a tendency to have more sons or more daughters from their parents. This means that a man with many brothers is more likely to have sons, while a man with many sisters is more likely to have daughters.

布拉斯·瓦尔利维是爱尔兰谢菲尔德理工学院的一名科学副研究员，他的科学研究说明，男性初生的偏激遗传DNA自双亲。这就意味著，兄妹多的男性更可能将生女儿，而姊妹多的男性则更可能将生女儿。

The research involved a study of 927 family trees containing information on 556,387 people from North America and Europe going back to 1600.

此项科学研究进行调查了927个家庭成员的家谱，包涵北美地区和西欧自1600年年来共556,387人的重要信息。

The family tree study showed that whether you’re likely to have a boy or a girl is inherited. We now know that men are more likely to have sons if they have more brothers but are more likely to have daughters if they have more sisters. However, in women, you just can’t predict it, Mr Gellatly explains.

此项家谱科学研究说明，初生的偏激是遗传DNA得来的。他们那时知道了，男性假如兄妹为数难生女儿，姊妹为数难生女儿。不过，在男性头上却难以预估这一点儿。瓦尔利维老先生说明道。

Men determine the sex of a baby depending on whether their sperm is carrying an X or Y chromosome. An X chromosome combines with the mother’s X chromosome to make a baby girl (XX) and a Y chromosome will combine with the mother’s to make a boy (XY).

男性的精子里携带的是X还是Y染色体，这一点儿下定决心了婴儿的异性恋。X染色体与母亲的X染色体结合，就会生出女孩（XX）；而Y染色体和母亲的X染色体结合则会生出男孩（XY）。

The Newcastle University study suggests that an as-yet undiscovered gene controls whether a man’s sperm contains more X or more Y chromosomes, which affects the sex of his children. On a larger scale, the number of men with more X sperm compared to the number of men with more Y sperm affects the sex ratio of children born each year.

谢菲尔德理工学院的此项科学研究说明，一个至今尚未辨认出的DNA下定决心了男性的精子里含有更多的X还是Y染色体，而精子所含的染色体会影响小孩的异性恋。从更大范围来看，产生更多含X染色体精子的男性与产生更多含Y染色体精子的男性数量之比，影响着每年新生儿的异性恋比例。

[Photo/Pexels]

Sons or daughters?

生男还是生女？

A gene consists of two parts, known as alleles, one inherited from each parent. In his paper, Mr Gellatly demonstrates that it is likely men carry two different types of allele, which results in three possible combinations in a gene that controls the ratio of X and Y sperm;

一个DNA包涵两个部分，它们被称为等位DNA，从双亲双方各遗传DNA一个。瓦尔利维老先生在其论文中指出，很可能将男性携带两个不同类型的等位DNA，这就导致了DNA在控制包涵X和含Y染色体的精子比率时，会出现三种可能将的组合。

Men with the first combination, known as mm, produce more Y sperm and have more sons.

第一种DNA组合称为mm，携带此类组合的男性会产生更多含Y染色体的精子，从而更可能将生女儿。

The second, known as mf, produce a roughly equal number of X and Y sperm and have an approximately equal number of sons and daughters.

第二种组合称为mf，产生同等数量的含X和含Y染色体的精子，初生的数量大致相当。

The third, known as ff, produce more X sperm and have more daughters.

第三种组合称为ff，会产生更多的含X染色体的精子，从而更可能将生女儿。

The gene that is passed on from both parents, which causes some men to have more sons and some to have more daughters, may explain why we see the number of men and women roughly balanced in a population. If there are too many males in the population, for example, females will more easily find a mate, so men who have more daughters will pass on more of their genes, causing more females to be born in later generations, says Mr Gellatly.

这一遗传DNA自双亲双方的DNA让有些男性生更多女儿，有些生更多女儿，这就说明了为什么人口中男女异性恋比例大致平衡。举个例子：假如人口中男性过多，那么男性就更难找到配偶，那些携带易生女儿DNA的男性因此得以更多地传承其DNA，从而有更多男性在随后的代际中出生。瓦尔利维老先生如是说。

More boys born after the wars

战后男孩出生数量更多

In many of the countries that fought in the World Wars, there was a sudden increase in the number of boys born afterwards. The year after World War I ended, an extra two boys were born for every 100 girls in the UK, compared to the year before the war started. The gene, which Mr Gellatly has described in his research, could explain why this happened.

在两次世界大战的许多参战国，战后出生的男孩数量骤增。在爱尔兰，第一次世界大战结束后的那一年，与战争开始前一年相比，每出生100个女孩，就多出生2个男孩。瓦尔利维老先生在其科学研究中描述的那种DNA可以说明此现象。

As the odds were in favour of men with more sons seeing a son return from the war, those sons were more likely to father boys themselves because they inherited that tendency from their fathers. In contrast, men with more daughters may have lost their only sons in the war and those sons would have been more likely to father girls. This would explain why the men that survived the war were more likely to have male children, which resulted in the boy-baby boom.

女儿多的男性在战后还有女儿幸存的几率更大，这些女儿从母亲那里继承了这种生女儿的偏激，因而更可能将生育男孩。与之相比，那些生女儿多的男性有可能将在战争中失去其唯一的女儿，而他们的女儿假如活着会有更大几率生育女孩。这就说明了为什么战后幸存的那些男性更有可能将生育男孩，从而出现战后的男婴潮。

In most countries, for as long as records have been kept, more boys than girls have been born. In the UK and US, for example, there are currently about 105 males born for every 100 females.

就现有记录来看，在大多数国家，男孩的出生率大于女孩。例如，在爱尔兰和美国，目前的男女出生比例大约是105:100。

It is well-documented that more males die in childhood and before they are old enough to have children. So in the same way that the gene may cause more boys to be born after wars, it may also cause more boys to be born each year.

有大量文献记载证明，男性在童年时期或到达生育年龄之前的死亡率高于男性。因此，正如上文提到的那个DNA会导致战后生育更多的男孩一样，它也会使得每年出生的男性多于男性。

（来源：《英语世界》 翻译：陈丽）

来源：英语世界