Everyone is afraid of something.
每个人都害怕一些事情。
Maybe you’re afraid of spiders, or heights, or dogs, or the dark.
也许你怕蜘蛛、怕高、怕狗、怕黑暗。
And traditionally, we've thought that's because you learned to be afraid.
传统上，我们认为这是因为你学会了害怕。
Probably because you had a bad run-in with something at some point.
可能是因为你在某个时候，碰到某件不愉快的事。
But there's a different idea out there that's been getting more attention lately:
但最近，有种不同的观点得到更多的关注：
the idea that fears aren’t just learned...they also can be inherited.
恐惧不仅是后天习得的，它们也可以遗传。
The idea isn’t new.
这并不是新观点。
Almost 150 years ago, Charles Darwin wrote about his toddler’s fear of large zoo animals,
大约150年前，查尔斯·达尔文写过一篇关于他蹒跚学步的孩子，害怕动物园里大型动物的文章，
which had never hurt the kid in his life.
这些动物在孩子的一生中从未伤害过他。
In fact, Darwin noted that many children’s fears have nothing to do with their experiences.
事实上，达尔文指出，许多孩子的恐惧与他们的经历无关。
So instead, he thought they had to be inherited, and that they were most likely related to real dangers in our evolutionary past.
相反，他认为它们是遗传的，而且很可能与我们进化史上真实存在的危险有关。
It sounds like a wild idea.
这个观点听起来挺疯狂。
Like, how do you inherit something as abstract as fear?
比如，你是如何继承恐惧这样抽象的东西的？
But over the last fifty years, researchers have been studying just how much fears have to do with inheritance and genetics.
但在过去50年里，研究人员一直在研究恐惧与遗传和基因学之间有多大关系。
And their results have been kind of surprising.
他们的结果令人惊讶。
In this work, they’ve put a lot of effort into understanding one extreme kind of fear, called a phobia.
在这项研究中，他们花了很多精力去理解一种极端的恐惧，叫做恐惧症。
Phobias are an intense fear of an object or situation.
恐惧症是对某个物体或某种情境产生的强烈恐惧。
And while you might throw around that word colloquially,
你可能会用白话来形容这个词，
psychologists define phobias as a type of anxiety disorder that typically lasts at least six months.
但心理学家把恐惧症界定为一种焦虑症，通常持续至少六个月。
Some common phobias include spiders, getting shots, or public speaking.
一些常见的恐惧症包括对蜘蛛、中弹，或者在公众场合演讲的恐惧。
And sure, for most of us, these are unpleasant things.
当然，对大多数人来说，这些都是不愉快的事情。
But for people with phobias, the fear can be so severe that it interferes with their ability to function.
但是，对于恐惧症患者来说，恐惧感会非常严重，以至于影响他们的正常生活。
Like, a person with a phobia of dogs can have a hard time just walking down the street.
比如，一个患有对狗的恐惧症的人就很难在街上散步。
Phobias aren’t uncommon, either.
恐惧症也并不少见。
It’s estimated that up to 15 percent of people will have one at some point in their life.
据估计，高达15%的人在一生的某个时候会有一种恐惧症。
Until 2002, scientists have generally thought that phobias were learned.
直到2002年，科学家们普遍认为恐惧症是后天习得的。
In other words, people developed them as a reaction to something bad happening.
换言之，人们将其发展为对糟糕事情的一种反应。
But that year, the authors of a literature review proposed that there was another pathway for developing phobias: genetics.
但在那一年，一篇文献综述的作者提出了患上恐惧症的另一种方式，即遗传学。
Like, the idea is you could be afraid of something you’ve never come across in your life…just because someone in your past had a bad experience with it.
比如说，你可能会害怕生活中从未遇到过的东西，而仅仅因为过去认识的某个人曾有过不好的经历。
Which...is a totally bizarre thing to think about.
这真是一件怪诞的事。
To get a sense of how much genes influence fear, scientists have begun looking at identical twins.
为了了解基因在多大程度上影响恐惧，科学家们开始研究同卵双胞胎。
Since identical twins have virtually identical DNA,
由于同卵双胞胎的DNA几乎完全相同，
researchers can figure out how heritable a fear is by comparing how often specific phobias appear in identical twins as opposed to other siblings or offspring.
研究人员可以通过比较同卵双胞胎与其兄弟姐妹或其子女的特定恐惧症出现的频率，找出恐惧的遗传性。
Because even though twins often have lots of similar experiences,
因为即使双胞胎经常有很多相似的经历，
they probably don’t share the types of experiences that cause phobias—like getting bitten by a dog or falling out of a tree.
但他们可能不会分享那些导致恐惧症的经历，比如遭到狗咬或从树上掉下来。
One 1998 study of 659 pairs of identical and fraternal twins in Australia looked at how many had a fear of blood.
1998年，澳大利亚的科学家们对659对同卵双胞胎和异卵双胞胎进行研究，调查有多少人恐惧血液。