PEOPLE who are genetically
predisposed to having children
earlier in life are less likely to
live to the age of 76, according
to an analysis of more than
270,000 people’s genomes.有人说生孩子早的人寿命更长久，但最近科学家通过对27万人的基因组调查后发现：生孩子早的人，活到76岁的可能性更小。Why we age is one of the biggest
evolutionary mysteries. You might
assume that natural selection
would lead to people passing on
genes that help you live longer,
thus giving more time to
reproduce, but there has been
no evidence to support this.衰老是人类进化过程中的一大谜题。我们可能认为自然选择把优良基因传下来，从而让人活得更久，所以人类就拥有更多的繁衍的时间。但事实并非如此。
One of the leading explanations
for this lack of evidence is that
genetic mutations that favour
reproducing earlier in life could
also result in a shorter lifespan, an
idea called antagonistic pleiotropy.其中一个证据就是让人生育早的遗传变异会让人寿命变短，这个想法叫做拮抗基因多效性。
“It’s because natural selection
largely cares about reproduction,”
says Jian zhi Zhang at the University
of Michigan. “So those mutations
that are beneficial for reproduction
but may be detrimental afterwards
would still be selected.”自然选择可能会促进人类生育，但有害的基因变异在后期仍会被选中。Seeking evidence relating
to antagonistic pleiotropy,
Zhang and Erping Long at the
Chinese Academy of Medical
Sciences analysed genomes from 276,406 people in the UK
Biobank, a long-term health study.
The selected participants were
born between1940 and 1969
and were of European ancestry.为了寻找拮抗基因多效性的支持证据，两位研究人员对27.6万生于1940年到1969年的祖先为欧洲的人进行了调查。For each person,the researchers
calculated a polygenic score, an
assessment of a mix of genetic
variants linked to better
reproductive health in early life.
The higher someone’s score, the
more likely they were to be fertile
for longer. They also collected
informationon lifespan: either
how long the participants lived
or howlong their parents lived for those who were still alive.研究人员对每个参与者进行了多基因分数评估。分数越高，说明参与者生育能力越强。同时，还对参与者的年龄进行了调查，其中也包括参与者父母的年龄。Zhang and Long found that
people who had higher polygenic
scores for reproductive health
had a lower probability of living
to 76 years old. There was no
specific reason forcusing this
age as a cut-off, says Zhang.调查发现：生育能力越强，生孩子越早，活到76岁的几率就越低。Those born earlier also tended
to have a lower polygenic score
than those born closer to 1969,
suggesting that traits that
enhance reproduction are
still being selected despite their
impact on longevity, says Zhang.出生早的人比出生晚的人多基因分数低，这说明生育基因遗传了下来。“Our findings are in strong
support of the antagonistic
pleiotropy hypothesis,” he says.
One potential mechanism is that
some gene variants that enhance
reproductive attributes may result
in disease later in life. For example,
one such variant, has been linked to cancers.研究人员说有些基因变异强化了生育功能，但会给一个人后期带来一些疾病。比如，其中一个变异基因与癌症有关。
“Whether our results apply
to African or Asian people,
we don’t know yet, but I think
we can expect to see this
pattern,” says Zhang. 但是研究人员还无法确定这个发现是否适用于非洲人或欧洲人。
It is also important to note that
other factors, including medical
advances, have led people to live
longer and have fewer children,
on average, says Zhang. “Genetic
changes are minute compared
to environmental factors.” ❚当然了，研究人员也说影响人类寿命的因素有很多，如医疗条件提升使得人们活得更长，生的孩子更少。但更重要的还有环境因素。遗传变化只是一个很小的影响因子。
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