When I was approximately nine weeks pregnant with my first child,
在我怀上第一个孩子约九周的时候，
I found out I'm a carrier for a fatal genetic disorder called Tay-Sachs disease.
我发现我是一种致命性遗传疾病的携带者，这种病叫做“泰伊-萨克斯二氏病”。
What this means is that one of the two copies of chromosome number 15 that I have in each of my cells has a genetic mutation.
这意味着在我的所有细胞中，每对15号染色体中的一条都携带了一个基因突变。
Because I still have one normal copy of this gene, the mutation doesn't affect me.
因为我的另一条染色体上还有这个基因的正常副本，所以这个突变并未影响我。
But if a baby inherits this mutation from both parents, if both copies of this particular gene don't function properly,
但如果婴儿从父母双方遗传了这个突变，如果两个这种基因都无法发挥正常功能，
it results in Tay-Sachs, an incurable disease that progressively shuts down the central nervous system and causes death by age five.
就会导致泰伊-萨克斯二氏病，这是一种无法治愈的疾病，会逐步关闭中枢神经系统，并导致患儿在五岁前死亡。
For many pregnant women, this news might produce a full-on panic.
对于很多孕妇，这个消息可能会造成极大恐慌。
But I knew something that helped keep me calm when I heard this bombshell about my own biology.
但当我听到关于我自身生理的这个爆炸性消息时，我知道的某件事情让我保持冷静。
I knew that my husband, whose ancestry isn't Eastern European Jewish like mine,
因为我的丈夫和我不同，他不像我有东欧犹太血统，
had a very low likelihood of also being a carrier for the Tay-Sachs mutation.
因此他也携带“泰伊-萨克斯”突变的几率非常低。
While the frequency of heterozygotes, individuals who have one normal copy of the gene and one mutated copy,
所谓杂合子指的是一对基因中有一个正常，另一个突变，
is about one out of 27 people among Jews of Ashkenazi descent, like me,
在像我这样的阿什肯纳兹犹太裔中，发生的概率大约是27分之一，
in most populations, only one in about 300 people carry the Tay-Sachs mutation.
但在大多数人群中，300多个人中才会有一个携带泰伊-萨克斯基因突变。
Thankfully, it turned out I was right not to worry too much.
谢天谢地，事实证明我是对的，无须太担心。
My husband isn't a carrier, and we now have two beautiful and healthy children.
我的丈夫不是携带者，而现在我们有两个健康可爱的孩子。
As I said, because of my Jewish background, I was aware of the unusually high rate of Tay-Sachs in the Ashkenazi population.
正如我所说的，因为我的犹太背景，我很清楚阿什肯纳兹犹太裔中泰伊-萨克斯病的风险异常高。
But it wasn't until a few years after my daughter was born when I created and taught a seminar in evolutionary medicine at Harvard,
但直到我女儿出生几年后，直到我在哈佛创立并教授一门进化医学的研讨课，
that I thought to ask, and discovered a possible answer to, the question "why?"
那时我才想提问“为什么？”并发现了一个可能的答案。
The process of evolution by natural selection typically eliminates harmful mutations.
自然选择的演化过程通常会淘汰有害的突变。
So how did this defective gene persist at all?
那么，这个有缺陷的基因是如何保留至今的呢？
And why is it found at such a high frequency within this particular population?
为什么它在这个特定人群当中发生的频率如此之高？
The perspective of evolutionary medicine offers valuable insight,
进化医学的观点提供了有价值的见解，
because it examines how and why humans' evolutionary past has left our bodies vulnerable to diseases and other problems today.
因为它在探究人类的进化历史如何及为什么会让我们的身体在面对当今的疾病和其他问题时如此脆弱。
In doing so, it demonstrates that natural selection doesn't always make our bodies better. It can't necessarily.
通过这些研究，表明了自然选择并不会总是让我们的身体变好。它不见得会。
But as I hope to illustrate with my own story, understanding the implications of your evolutionary past can help enrich your personal health.
但我希望能用我自己的故事来说明，了解你的进化历史的影响可以有助于改善你的个人健康。
When I started investigating Tay-Sachs using an evolutionary perspective, I came across an intriguing hypothesis.
当我开始从进化的角度研究泰伊-萨克斯病时，我发现了一个有趣的假设。
The unusually high rate of the Tay-Sachs mutation in Ashkenazi Jews today
泰伊-萨克斯基因突变在今天的阿什肯纳兹犹太人中发生率异常之高，
may relate to advantages the mutation gave this population in the past.
可能与过去这个突变为这个种群带来的好处有关。
Now I'm sure some of you are thinking, "I'm sorry, did you just suggest that this disease-causing mutation had beneficial effects?"
我相信你们中的一些人会心想，“不好意思，你刚才难道想说，这种会导致疾病的基因突变还能有好处？”
Yeah, I did. Certainly not for individuals who inherited two copies of the mutation and had Tay-Sachs.
没错，就是这个意思。对于那些遗传了两个突变副本、得了泰伊-萨克斯病的人来说，当然没有好处。
But under certain circumstances, people like me, who had only one faulty gene copy,
但在某些情况下，像我这样只有一个错误的基因副本的人，
may have been more likely to survive, reproduce and pass on their genetic material, including that mutated gene.
可能更容易生存、繁殖，并传递他们的遗传物质，其中包括那个突变的基因。
This idea that there can be circumstances in which heterozygotes are better off might sound familiar to some of you.
此观点认为，在某些情况下，杂合子会出落得更好，听起来可能有些耳熟。
Evolutionary biologists call this phenomenon heterozygote advantage.
进化生物学家将这种现象称为“杂合子优势”。
And it explains, for example, why carriers of sickle cell anemia
它能够解释，例如，为什么镰状细胞性贫血的携带者，
are more common among some African and Asian populations or those with ancestry from these tropical regions.
在一些非洲和亚洲人群中，或是祖先来自这些热带地区的人群中更为常见。
In these geographic regions, malaria poses significant risks to health.
在这些地理区域，疟疾对健康构成重大威胁。
The parasite that causes malaria, though, can only complete its life cycle in normal, round red blood cells.
但是导致疟疾的寄生虫只能在正常的圆形红细胞中完成其生命周期。
By changing the shape of a person's red blood cells, the sickle cell mutation confers protection against malaria.
通过改变人体红细胞的形状，镰状细胞的突变能够保护人类，抵抗疟疾。
People with the mutation aren't less likely to get bitten by the mosquitoes that transmit the disease,
带有这种突变的人仍有同等几率被传播疟疾的蚊子叮咬，
but they are less likely to get sick or die as a result.
但他们因此患病或死亡的几率却更低。
Being a carrier for sickle cell anemia is therefore the best possible genetic option in a malarial environment.
因此，在疟疾肆虐的环境中，携带镰状细胞性贫血是最好的遗传选项。
Carriers are less susceptible to malaria, because they make some sickled red blood cells,
携带者不太容易感染疟疾，因为他们会产生一些镰状红细胞，
but they make enough normal red blood cells that they aren't negatively affected by sickle cell anemia.
但也能生成足够的正常红细胞，这样就不会受到镰状细胞性贫血的负面影响。
Now in my case, the defective gene I carry won't protect me against malaria.
在我的例子中，我携带的缺陷基因不能保护我免受疟疾的侵害。
But the unusual prevalence of the Tay-Sachs mutation in Ashkenazi populations may be another example of heterozygote advantage.
但是泰伊-萨克斯突变在阿什肯纳兹犹太人群中的异常流行，可能是另一个杂合子优势的案例。
In this case, increasing resistance to tuberculosis.
在这个例子里，则是增加了对肺结核的抵抗力。
The first hint of a possible relationship between Tay-Sachs and tuberculosis came in the 1970s,
泰伊-萨克斯突变和肺结核之间可能存在联系的第一个迹象出现在20世纪70年代，
when researchers published data showing that among the Eastern European-born grandparents of a sample of American Ashkenazi children born with Tay-Sachs,
当时研究人员分析了一个先天患有泰伊-萨克斯病的美籍阿什肯纳兹犹太儿童样本，数据显示，他们东欧出身的祖父母中，
tuberculosis was an exceedingly rare cause of death.
结核病是一种极其罕见的死亡原因。
In fact, only one out of these 306 grandparents had died of TB,
事实上，306位祖父母中只有一位死于肺结核，
despite the fact that in the early 20th century, TB caused up to 20 percent of deaths in large Eastern European cities.
尽管在20世纪早期，在东欧的大城市里，结核病导致了超过20%的死因。
Now on the one hand, these results weren't surprising.
一方面，这些结果并不出乎意料。
People had already recognized that while Jews and non-Jews in Europe had been equally likely to contract TB during this time,
人们已经认识到，虽说当时欧洲的犹太人和非犹太人感染肺结核的可能性是相同的，
the death rate among non-Jews was twice as high.
非犹太人的死亡率却是犹太人的两倍。
But the hypothesis that these Ashkenazi grandparents had been less likely to die of TB specifically
但是这个假设指出，这些德系犹太人祖父母死于结核病的几率更低的具体原因，
because at least some of them were Tay-Sachs carriers was novel and compelling.
在于他们中至少有一部分是泰伊-萨克斯携带者，这个假说非常新颖且有力。
The data hinted that the persistence of the Tay-Sachs mutation among Ashkenazi Jews
这些数据暗示了泰伊-萨克斯突变在德系犹太人当中持续存在，
might be explained by the benefits of being a carrier in an environment where tuberculosis was prevalent.
也许是因为在结核病流行的环境中，携带这种基因是有益处的。
You'll notice, though, that this explanation only fills in part of the puzzle.
不过，你会注意到，这种解释只解答了部分谜团。
Even if the Tay-Sachs mutation persisted because carriers were more likely to survive, reproduce and pass on their genetic material,
即使泰伊-萨克斯突变持续存在是因为携带者更有可能存活下来，繁殖并传承他们的遗传物质，
why did this resistance mechanism proliferate among the Ashkenazi population in particular?
为什么这种抵抗机制只在阿什肯纳兹犹太人中得以扩增？
One possibility is that the genes and health of Eastern European Jews
一种可能性是东欧犹太人的基因和健康
were affected not simply by geography but also by historical and cultural factors.
不只是受地理因素的影响，还受到历史文化因素的影响。
At various points in history this population was forced to live in crowded urban ghettos with poor sanitation.
在不同的历史时期，这些人被迫住在拥挤的城市贫民窟，这些地方卫生条件恶劣。
Ideal conditions for the tuberculosis bacterium to thrive.
正是结核杆菌生长的理想温床。
In these environments, where TB posed an especially high threat,
在这些结核病构成了特别高威胁的环境中，
those individuals who were not carriers of any genetic protection would have been more likely to die.
那些没有携带任何基因保护的个人更有可能死亡。

This winnowing effect together with a strong cultural predilection for marrying and reproducing only within the Ashkenazi community,
这个风选效应再加上阿什肯纳兹犹太人只和同族人结婚生子的强烈文化偏好，
would have amplified the relative frequency of carriers,
这会扩大携带者的相对频率，
boosting TB resistance but increasing the incidence of Tay-Sachs as an unfortunate side effect.
提高对肺结核的抵抗力，但不幸的副作用就是泰伊-萨克斯病的发病率会增加。
Studies from the 1980s support this idea.
20世纪80年代的研究证实了这一观点。
The segment of the American Jewish population that had the highest frequency of Tay-Sachs carriers
美籍犹太人中泰伊-萨克斯携带频率最高的人群，
traced their descent to those European countries where the incidence of TB was highest.
能把他们的血统追溯到那些结核病发病率最高的欧洲国家。
The benefits of being a Tay-Sachs carrier were highest in those places where the risk of death due to TB was greatest.
在那些死于结核病的风险最大的地方，身为泰伊-萨克斯携带者的好处也越大。
And while it was unclear in the 1970s or '80s how exactly the Tay-Sachs mutation offered protection against TB,
虽然在七八十年代还不清楚泰伊-萨克斯突变究竟是如何预防结核病的，
recent work has identified how the mutation increases cellular defenses against the bacterium.
最近的研究发现了这个突变能如何增加细胞对结核菌的防御。
So heterozygote advantage can help explain why problematic versions of genes persist at high frequencies in certain populations.
因此杂合子优势有助于解释为什么有问题的基因在特定人群中仍高频率地持续存在。
But this is only one of the contributions evolutionary medicine can make in helping us understand human health.
但这只是进化医学为帮助我们了解人类健康所能做出的贡献之一。
As I mentioned earlier, this field challenges the notion that our bodies should have gotten better over time.
如之前所说，这个领域挑战了“人类的身体应当越变越好”的观念。
An idea that often stems from a misconception of how evolution works.
这个想法通常源于对进化的误解。
In a nutshell, there are three basic reasons why human bodies, including yours and mine,
简而言之，有三个基本原因导致了包括你我的身体，
remain vulnerable to diseases and other health problems today.
现今仍然容易受到疾病和其他健康问题的困扰。
Natural selection acts slowly, there are limitations to the changes it can make and it optimizes for reproductive success, not health.
自然选择的过程是缓慢的；它所能做的改变是有限的；它优化的是繁殖成功率，而不是健康。
The way the pace of natural selection affects human health is probably most obvious in people's relationship with infectious pathogens.
自然选择的速度影响人类健康的方式在人类与传染性病原体的关系中可能是最明显的。
We're in a constant arms race with bacteria and viruses.
我们一直在与细菌和病毒进行军备竞赛。
Our immune system is continuously evolving to limit their ability to infect,
我们的免疫系统不断进化，以限制它们的感染能力，
and they are continuously developing ways to outmaneuver our defenses.
而它们则在不断开发各种方法以突破我们的防线。
And our species is at a distinct disadvantage due to our long lives and slow reproduction.
而我们人类处于明显的劣势，因为我们的寿命长，繁殖慢。
In the time it takes us to evolve one mechanism of resistance, a pathogenic species will go through millions of generations,
在我们进化出一种抗性机制的时间里，一个致病物种早已经历了数百万代，
giving it ample time to evolve, so it can continue using our bodies as a host.
给它提供了足够的时间来进化，使得它可以继续把我们的身体当做宿主。
Now what does it mean that there are limitations to the changes natural selection can make?
那么，自然选择能做出的改变有限又是什么意思呢？
Again, my examples of heterozygote advantage offer a useful illustration.
同样，我举出的杂合子优势的例子能提供有用的佐证。
In terms of resisting TB and malaria, the physiological effects of the Tay-Sachs and sickle cell anemia mutations are good.
在抵御结核病和疟疾方面，泰伊-萨克斯和镰状细胞性贫血突变的生理效果是有利的。
Taken to their extremes, though, they cause significant problems.
但是，当这些突变走了极端，就会导致严重的问题。
This delicate balance highlights the constraints inherent in the human body,
这个微妙的平衡突显了人体自身的局限，
and the fact that the evolutionary process must work with the materials already available.
也说明了演化的过程必须利用现有的素材。
In many instances, a change that improves survival or reproduction in one sense may have cascading effects that carry their own risk.
在很多情况下，一个能在某方面改善生存或繁衍的变化，却会衍生出一连串有风险的效应。
Evolution isn't an engineer that starts from scratch to create optimal solutions to individual problems.
进化并不像是工程师从零开始，针对个别问题创造最优解法。
Evolution is all about compromise. It's also important to remember, when considering our bodies' vulnerabilities,
进化全是关乎妥协。我们还需谨记，在考虑到我们身体的弱点时，
that from an evolutionary perspective, health isn't the most important currency. Reproduction is.
从进化的角度看来，健康并不是最重要的通货。繁殖才是。
Success is measured not by how healthy an individual is, or by how long she lives,
成功的标尺并非个体有多健康，或者能活多久，
but by how many copies of her genes she passes to the next generation.
而是能向下一代传递多少份基因。
This explains why a mutation like the one that causes Huntington's disease,
这解释了为什么某个基因突变，
another degenerative neurological disorder, hasn't been eliminated by natural selection.
例如导致另一种神经退化障碍亨丁顿舞蹈症的突变，并没有被自然选择淘汰。
The mutation's detrimental effects usually don't appear until after the typical age of reproduction,
这个突变的毁灭性效果通常在育龄之后才开始浮现，
when affected individuals have already passed on their genes.
这时患者已经把他们的基因遗传下去了。
As a whole, the biomedical community focuses on proximate explanations and uses them to shape treatment approaches.
总体来说，生物医学领域的焦点在于“近因解释”，并利用它们打造治疗方案。
Proximate explanations for health conditions consider the immediate factors:
健康问题的近因解释会考虑到直接因素：
What's going on inside someone's body right now that caused a particular problem.
某人身体内此时此刻正在发生什么事情导致了某个特定问题。
Nearsightedness, for example, is usually the result of changes to the shape of the eye and can be easily corrected with glasses.
比如说，近视通常是因为眼球形状发生了改变，可以用眼镜轻松地矫正。
But as with the genetic conditions I've discussed, a proximate explanation only provides part of the bigger picture.
但与我讨论的遗传病症如出一辙，近因解释只涵盖了全貌的一部分。
Adopting an evolutionary perspective to consider the broader question of why do we have this problem to begin with
采取进化的视角去更广泛地思考我们一开始为什么会有这个问题，
what evolutionary medicine calls the ultimate perspective -- can give us insight into nonimmediate factors that affect our health.
也是进化医学所说的“终极因”，能让我们洞察影响健康的非直接因素。
This is crucial, because it can suggest ways by which you can mitigate your own risk or that of friends and family.
这是至关重要的，因为从中可以找出一些方法来帮助你自己或是家人朋友将健康风险降低。
In the case of nearsightedness, some research suggests that one reason it's becoming more common in some populations is that
在近视的例子里，有部分研究表明近视在某些人群中变得更普遍的原因之一是，
many people today, including most of us in this room, spend far more time reading, writing and engaging with various types of screen
现在的很多人，包括这个房间内的大多数人，花更多时间读写以及接触各式屏幕，
than we do outside, interacting with the world on a bigger scale.
而不是在户外和更广阔的的世界互动。
In evolutionary terms, this is a recent change.
以进化的角度来看，这是最近才发生的变化。
For most of human evolutionary history, people used their vision across a broader landscape,
人类进化史的大部分时间里，人们的视力都用在了更广阔的的景观中，
spending more time in activities like hunting and gathering.
花更多时间进行狩猎与采集这样的活动。
The increase in recent years in what's termed "near work," focusing intensely on objects directly in front of us for long periods of time,
近年来，“近距离用眼工作”的增加让我们对面前的近物进行长时间、高强度的聚焦，
strains our eyes differently and affects the physical shape of the eye.
以不同的方式让我们用眼疲劳，影响了眼球的物理形状。
When we put all these pieces together, this ultimate explanation for nearsightedness
当我们把这些信息串联在一起，就能得出近视的“终极因”解释，
that environmental and behavioral change impact the way we use our eyes -- helps us better understand the proximate cause.
环境和行为的变化影响了我们的用眼方式--这个解释能帮助我们更好地理解近因。
And an inescapable conclusion emerges -- my mother was right, I probably should have spent a little less time with my nose in a book.
随之浮现的是一个无可避免的结论--我妈妈是对的，我或许应该少花点时间埋头看书。
This is just one of many possible examples.
这只是许许多多例子中的一个。
So the next time you or a loved one are faced with a health challenge,
下一次你或者你心爱的人面临健康挑战的时候，
whether it's obesity or diabetes, an autoimmune disorder, or a knee or back injury,
无论是肥胖症、糖尿病，自身免疫疾病，还是膝盖或腰背受伤，
I encourage you to think about what an ultimate perspective can contribute.
我鼓励你想想一个终极因的角度能提供什么帮助。
Understanding that your health is affected not just by what's going on in your body right now,
理解你的健康不仅受到你身体此刻的状况影响，
but also by your genetic inheritance, culture and history,
同时也受到你的遗传、文化和历史影响，
can help you make more informed decisions about predispositions, risks and treatments.
能帮助你在考虑遗传基因、风险和治疗时，做出更加明智的决定。
As for me, I won't claim that an evolutionary medicine perspective has always directly influenced my decisions, such as my choice of spouse.
对于我来说，我并不会声称进化医学的角度总会直接影响我的决定，比如说，我对配偶的选择。
It turned out, though, that not following the traditional practice of marrying within the Jewish community
但结果是，我没有遵从在犹太人群体内结婚的传统，
ultimately worked in my favor genetically, reducing the odds of me having a baby with Tay-Sachs.
最终在遗传方面对我有利，减少了我的孩子患上泰伊-萨克斯病的几率。
It's a great example of why not every set of Ashkenazi parents should hope that their daughter marries "a nice Jewish boy."
这个绝佳的例子也说明了，为什么并不是每对阿什肯纳齐犹太父母都应希望他们的女儿嫁给“一个犹太好男孩”。
More importantly, though, the experience of learning about my own genes taught me to think differently about health in the long run,
但更重要的是，了解我自己基因的经历教会我以不同的方式长远地思考健康问题，
and I hope sharing my story inspires you to do the same. Thank you.
我希望通过分享我的故事，也能启发各位这么做。谢谢。