第1段

To biomedical researchers all over the world, twins offer a precious opportunity to untangle the influence of genes and the environment – of nature and nurture. Because identical twins come from a single fertilized egg that splits into two, they share virtually the same genetic code. Any differences between them – one twin having younger looking skin, for example – must be due to environmental factors such as less time spent in the sun.

对世界各地的生物医学研究人员来说，双胞胎提供了一个宝贵的机会，可以解开基因和环境、自然和培养之间的影响。因为同卵双胞胎来自一个受精卵分裂成两个，它们几乎共享相同的基因密码。它们之间的任何差异，比如一个双胞胎看起来皮肤更年轻，必须是由于环境因素，比如在阳光下花费的时间较少。

第2段

Alternatively, by comparing the experiences of identical twins with those of fraternal twins, who come from separate eggs and share on average half their DNA, researchers can quantify the extent to which our genes affect our lives. If identical twins are more similar to each other with respect to an ailment than fraternal twins are, then vulnerability to the disease must be rooted at least in part in heredity.

另一方面，通过比较同卵双胞胎和异卵双胞胎的经历，可以量化我们的基因对我们生活的影响程度。如果同卵双胞胎在某种疾病方面比异卵双胞胎更相似，那么对该疾病的易感性至少部分必须根植于遗传。

第3段

These two lines of research – studying the differences between identical twins to pinpoint the influence of environment, and comparing identical twins with fraternal ones to measure the role of inheritance – have been crucial to understanding the interplay of nature and nurture in determining our personalities, behavior, and vulnerability to disease.

这两种研究方法——研究同卵双胞胎之间的差异以确定环境的影响，以及比较同卵双胞胎与异卵双胞胎以测量遗传的作用——对于了解自然和培养在决定我们的个性、行为和易感性方面的相互作用至关重要。

第4段

The idea of using twins to measure the influence of heredity dates back to 1875, when the English scientist Francis Galton first suggested the approach (and coined the phrase ‘nature and nurture‘). But twin studies took a surprising twist in the 1980s, with the arrival of studies into identical twins who had been separated at birth and reunited as adults. Over two decades 137 sets of twins eventually visited Thomas Bouchard’s lab in what became known as the Minnesota Study of Twins Reared Apart. Numerous tests were carried out on the twins, and they were each asked more than 15,000 questions.

利用双胞胎来衡量遗传影响的想法可以追溯到1875年，当时英国科学家弗朗西斯·高尔顿首次提出了这种方法（并创造了“自然和培养”的短语）。但在20世纪80年代，双胞胎研究出现了令人惊讶的转折，通过研究分别在出生时分开并在成年时重聚的同卵双胞胎。长达20多年的时间，137对双胞胎最终访问了托马斯·布查德的实验室，这就是后来被称为“明尼苏达双胞胎分别养育研究”的研究。在双胞胎身上进行了大量测试，每个人被问了超过15,000个问题。

第5段

Bouchard and his colleagues used this mountain of data to identify how far twins were affected by their genetic makeup. The key to their approach was a statistical concept called heritability. In broad terms, the heritability of a trait measures the extent to which differences among members of a population can be explained by differences in their genetics. And wherever Bouchard and other scientists looked, it seemed, they found the invisible hand of genetic influence helping to shape our lives.

布查德和他的同事们利用这些大量数据来确定双胞胎受他们的基因组成影响的程度。他们的方法的关键是一个叫做遗传力的统计概念。大致上，一个特征的遗传力衡量了人口中成员之间的差异可以通过其基因差异来解释的程度。而无论布查德和其他科学家看哪里，似乎都会发现基因影响无形地帮助塑造我们的生活。

第6段

Lately, however, twin studies have helped lead scientists to a radical new conclusion: that nature and nurture are not the only elemental forces at work. According to a recent field called epigenetics, there is a third factor also in play, one that in some cases serves as a bridge between the environment and our genes, and in others operates on its own to shape who we are.

然而，最近，双胞胎研究帮助科学家得出了一个激进的新结论：自然和培养并不是唯一起作用的基本力量。根据最近的一种称为表观遗传学的领域，还有第三个因素在起作用，有时作为环境和我们的基因之间的桥梁，在其他情况下独立地塑造我们是谁。

第7段

Epigenetic processes are chemical reactions tied to neither nature nor nurture but representing what researchers have called a ‘third component‘. These reactions influence how our genetic code is expressed: how each gene is strengthened or weakened, even turned on or off, to build our bones, brains and all the other parts of our bodies.

表观遗传过程是与自然和培养无关但代表研究人员所称的“第三成分”的化学反应。这些反应影响我们的基因密码的表达方式：每个基因是如何加强或减弱的，甚至打开或关闭，以建造我们的骨骼、大脑和身体的所有其他部分。

第8段

If you think of our DNA as an immense piano keyboard and our genes as the keys – each key symbolizing a segment of DNA responsible for a particular note, or trait, and all the keys combining to make us who we are – then epigenetic processes determine when and how each key can be struck, changing the tune being played.

如果你把我们的DNA想象成一个巨大的钢琴键盘，我们的基因就是键——每个键象征着负责特定音符或特质的DNA片段，所有的键结合在一起构成了我们的样子——那么表观遗传过程决定了每个键何时以及如何被触发，改变了正在演奏的曲调。

第9段

One way the study of epigenetics is revolutionizing our understanding of biology is by revealing a mechanism by which the environment directly impacts on genes. Studies of animals, for example, have shown that when a rat experiences stress during pregnancy, it can cause epigenetic changes in a fetus that lead to behavioral problems as the rodent grows up. Other epigenetic processes appear to occur randomly, while others are normal, such as those that guide embryonic cells as they become heart, brain, or liver cells, for example.

表观遗传学研究正在通过揭示环境如何直接影响基因的机制来彻底改变我们对生物学的理解。例如，对动物的研究表明，当一只老鼠在怀孕期间经历压力时，可能导致胎儿的表观遗传变化，这些变化会导致老鼠长大后产生行为问题。其他表观遗传过程似乎是随机发生的，而其他是正常的，比如指导胚胎细胞成为心脏、大脑或肝脏细胞的过程。

第10段

Geneticist Danielle Reed has worked with many twins over the years and thought deeply about what twin studies have taught us. ‘It’s very clear when you look at twins that much of what they share is hardwired,’ she says. ‘Many things about them are absolutely the same and unalterable. But it’s also clear, when you get to know them, that other things about them are different. Epigenetics is the origin of a lot of those differences, in my view.’

遗传学家丹妮尔·里德多年来一直与许多双胞胎一起工作，并深入思考双胞胎研究教会我们什么。她说：“当你看双胞胎时，很明显，他们许多共享的东西是固有的。”她说：“他们的许多东西绝对是相同的且无法改变的。但是，当你开始了解他们时，你会发现他们的其他方面是不同的。在我看来，表观遗传学是这些差异的起源。”

第11段

Reed credits Thomas Bouchard’s work for today’s surge in twin studies. ‘He was the trailblazer,’ she says. ‘We forget that 50 years ago things like heart disease were thought to be caused entirely by lifestyle. Schizophrenia was thought to be due to poor mothering. Twin studies have allowed us to be more reflective about what people are actually born with and what’s caused by experience.’

里德将今天的双胞胎研究激增归功于托马斯·布查德的工作。她说：“他是开路先锋。”她说：“我们忘记了50年前，像心脏病这样的疾病被认为完全是由生活方式引起的。精神分裂症被认为是由于母亲的不良抚养引起的。双胞胎研究使我们能够更深入地思考人们实际上是出生时携带了什么以及经验造成了什么。”

第12段

Having said that, Reed adds, the latest work in epigenetics promises to take our understanding even further. ‘What I like to say is that nature writes some things in pencil and some things in pen,’ she says. ‘Things written in pen you can’t change. That’s DNA. But things written in pencil you can. That’s epigenetics. Now that we’re actually able to look at the DNA and see where the pencil writings are, it’s sort of a whole new world.’