【双语】 TED演讲：为什么有些人是左撇子？

最英语 2024-01-09

当今世界上大约十分之一的人口是左撇子。为什么只有这么一小部分人是左撇子?又为什么会存在左撇子呢?

Why are some people left handed？

If you know an older left-handed person,chances are they had to learn to write or eat with their right hand.And in many parts of the world,it's still common practice to force children to use their"proper"hand.

如果你认识一个比你大的左撇子，他们很可能曾被迫学习过用右手写字或吃饭。在世界许多地方，依旧有惯例强迫孩子使用“合适”的手。

Even the word for right also means correct or good,not just in English,but many other languages,too.But if being left-handed is so wrong,then why does it happen in the first place?Today,about 1/10 of the world's population are left-handed.

就连“右”字，在英语里也代表着正确和好。不仅仅是在英语中，很多其他语言也是。但如果左撇子是错的，那为什么会有左撇子出现呢？今天，世界上大约十分之一的人口是左撇子。

Archeological evidence shows that it's been that way for as long as 500,000 years,with about 10%of human remains showing the associated differences in arm length and bone density,and some ancient tools and artifacts showing evidence of left-hand use.And despite what many may think,handedness is not a choice.

考古证据表明，这种情况已经持续了50万年之久，约有10%的人在手臂长度和骨密度上显现出差异区别。还有一些古代工具和手工艺品也显示了左撇子存在的证据。尽管很多人认为，用手习惯不是一种选择。

It can be predicted even before birth based on the fetus'position in the womb.So,if handedness is inborn,does that mean it's genetic?Well,yes and no.Identical twins,who have the same genes,can have different dominant hands.In fact,this happens as often as it does with any other sibling pair.

但在出生前根据胎儿在子宫里的位置就可以预测。所以，如果用手习惯是天生的，这意味着它是基因定的吗？好吧，是也不是。同卵双胞胎，有相同的基因，也会产生不同的主导手。事实上，这与其他同胞对的发生概率一样。

But the chances of being right or left-handed are determined by the handedness of your parents in surprisingly consistent ratios.If your father was left-handed but your mother was right-handed,you have a 17%chance of being born left-handed,while two righties will have a left-handed child only 10%of the time.

你是左撇子还是右撇子取决于父母的用手习惯这有惊人的统一数据。如果你父亲是左撇子，而你母亲是右撇子，你是左撇子的几率是17%，而父母都是右撇子只有10%的机率会生一个左撇子。

Handedness seems to be determined by a roll of the dice,but the odds are set by your genes.All of this implies there's a reason that evolution has produced this small proportion of lefties,and maintained it over the course of millennia.

看起来用手习惯像掷骰子一样，但几率是由你的基因决定的。这一切的原由是，进化产生了这小部分的左撇子，并维持了几千年之久。

And while there have been several theories attempting to explain why handedness exists in the first place,or why most people are right-handed,a recent mathematical model suggests that the actual ratio reflects a balance between competitive and cooperative pressures on human evolution.

尽管有几个理论试图解释为什么一开始有用手习惯存在，或者为什么大多数人都是右撇子，最近的一个数学模型表明现实比例反应了人类进化中竞争和合作压力造成的人数平衡。

The benefits of being left-handed are clearest in activities involving an opponent,like combat or competitive sports.For example,about 50%of top hitters in baseball have been left-handed.Why?Think of it as a surprise advantage.

左撇子的好处在关注敌人的活动中最为明显，比如拳击或竞技运动。例如，大约50%的棒球顶级击球手是左撇子。为什么？那会是很特殊的优势。

Because lefties are a minority to begin with,both right-handed and left-handed competitors will spend most of their time encountering and practicing against righties.So when the two face each other,the left-hander will be better prepared against this right-handed opponent,while the righty will be thrown off.

左撇子很小众，左撇子和右撇子的选手都会花大量的时间练习对抗右撇子。所以当两个人面对面对抗的时候，左撇子会更熟练地对抗右撇子对手，而右撇子的就无力对抗了。

This fighting hypothesis,where an imbalance in the population results in an advantage for left-handed fighters or athletes,is an example of negative frequency-dependent selection.But according to the principles of evolution,groups that have a relative advantage tend to grow until that advantage disappears.

这个战斗假设，因人数上的不平均造成左撇子的战士或者运动员有优势，是一个很好的负频率相关选择的例子。但根据进化原理，有相关优势的组群会发展至优势消失。

If people were only fighting and competing throughout human evolution,natural selection would lead to more lefties being the ones that made it until there were so many of them,that it was no longer a rare asset.So in a purely competitive world,50%of the population would be left-handed.

如果在人类进化中只有战斗和竞争，自然选择会导致左撇子的数量从很少变为很多，直到他们不再是稀有资源。所以在一个纯粹竞争的世界里，50%的人口将是左撇子。

But human evolution has been shaped by cooperation,as well as competition.And cooperative pressure pushes handedness distribution in the opposite direction.In golf,where performance doesn't depend on the opponent,only 4%of top players are left-handed,an example of the wider phenomenon of tool sharing.

但人类的进化有合作，和竞争。由于合作的压力造成用手习惯往相反的方向。在高尔夫球赛中，选手的表现不取决于对手，所以只有4%的顶级选手是左撇子，这是个更广泛现象的工具共享。

Just as young potential golfers can more easily find a set of right-handed clubs,many of the important instruments that have shaped society were designed for the right-handed majority.Because lefties are worse at using these tools,and suffer from higher accident rates,they would be less successful in a purely cooperative world,eventually disappearing from the population.

像年轻有潜力的高尔夫手们更容易找到右手为主的俱乐部，很多重要的装备都是为大众的右手选手设计的，因为左撇子都用不惯这些装备，而且高失误率，会使他们在纯合作环境里吃亏。最终造成人数上锐减。

So by correctly predicting the distribution of left-handed people in the general population,as well as matching data from various sports,the model indicates that the persistence of lefties as a small but stable minority reflects an equilibrium that comes from competitive and cooperative effects playing out simultaneously over time.

为了能正确预测左撇子在人群中的分布，以及与各项运动中的数据配对，该模型表明，左撇子群体小而且数量稳定，反应了一种平衡，这种平衡受竞争和合作的影响，随着时间的推移同时进行着。

And the most intriguing thing is what the numbers can tell us about various populations.From the skewed distribution of pawedness in cooperative animals,to the slightly larger percentage of lefties in competitive hunter-gatherer societies,we may even find that the answers to some puzzles of early human evolution are already in our hands.

最有趣的是这些数字能告诉我们很多关于人群数量变化中包含的信息。从有爪动物合作的倾斜分布，到合作狩猎社会里比重稍大的左撇子。我们会发现有关早期人类进化的某些难题的答案就在我们手中。

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