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为什么有人是左撇子 – 译学馆
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为什么有人是左撇子

Why are some people left-handed? - Daniel M. Abrams

如果你认识年龄较大的左撇子
If you know an older left-handed person,
很可能他们需要学习用右手写字或吃饭
chances are they had to learn to write or eat with their right hand.
在世界上的很多地方
And in many parts of the world,
强迫孩子用“合适”的手做事仍是一种寻常惯例
it’s still common practice to forcechildren to use their”proper” hand.
甚至“右”这个词也有“正确” “好”的意思
Even the word for rightalso means correct or good,
不仅在英语里 其它很多语言也是如此
not just in English,but many other languages, too.
但如果左撇子这么不正确
But if being left-handed is so wrong,
那为什么起初它会存在呢?
then why does it happenin the first place?
现今 世界上大约有1/10的人是左撇子
Today, about 1/10 of the world’spopulation are left-handed.
考古学证据表明 这种现象
Archeological evidence showsthat it’s been that way
已经持续至少50万年了
for as long as 500,000 years,
大约10%的人类遗骸展示了臂长
with about 10 % of human remains showing the associated differences
和骨密度的相关差异
in arm length and bone density,
一些古代工具和作品也展示了被左撇子使用的证据
and some ancient tools and artifactsshowing evidence of left-hand use.
不管人们会怎样想 惯用哪只手并不是一种选择
And despite what many may think,handedness is not a choice.
这甚至能够根据胎儿出生前
It can be predicted even before birth based on
在子宫中的胎位预测出来
the fetus’ position in the womb.
那么 如果惯用哪只手是天生的 那意味着它是遗传的吗?
So, if handedness is inborn,does that mean it’s genetic?
说是也不是
Well, yes and no.
同卵双胞胎有相同的基因 可能有不同的惯用手
Identical twins, who have the same genes, can have different dominant hands.
事实上 这种情况也经常
In fact, this happens as often as it does
发生在其他兄弟姐妹身上
with any other sibling pair.
但你惯用右手还是左手的几率
But the chances of beingright or left-handed
是由你父母的惯用手 出人意料的
are determined by the handednessof your parents
一致性决定的
in surprisingly consistent ratios.
如果你的父亲是左撇子 但母亲是右撇子
If your father was left-handedbut your mother was right-handed,
你有17%的几率天生左撇子
you have a 17% chanceof being born left-handed,
而两个右撇子的孩子为左撇子的几率只有10%
while two righties will have a left-handed child only 10 % of the time.
惯用哪只手看上去像由骰子滚动(随机)决定的
Handedness seems to be determinedby a roll of the dice,
但几率是由你的基因决定的
but the odds are set by your genes.
所有这一切都意味着进化论
All of this implies there’s a reason
制造了这小部分的左撇子
that evolution has produced this small proportion of lefties,
并且保留几千年是有道理的
and maintained itover the course of millennia.
尽管已经有一些学说理论
And while there have been several theories
尝试解释为什么从一开始就存在了惯用手
attempting to explain why handednessexists in the first place,
或是为什么大多数人都是右撇子
or why most people are right-handed,
最近有一个数学模型提出
a recent mathematical model suggests
实际比率反映了人类进化中
that the actual ratio reflects a balance
竞争与合作压力的平衡
between competitive and cooperativepressures on human evolution.
左撇子的优势在
The benefits of being left-handed are clearest
有对手的运动里最为明显
in activities involving an opponent,
比如搏斗或竞技体育中
like combat or competitive sports.
例如 棒球运动中大约有50%的顶尖击球手是左撇子
For example, about 50 % of top hitters in baseball have been left-handed.
为什么?
Why?
把它当作一个令人惊喜的有利条件
Think of it as a surprise advantage.
因为左撇子本来就是少数群体
Because lefties are a minorityto begin with,
而右撇子和左撇子同为竞争者
both right-handedand left-handed competitors
他们大部分时间都会
will spend most of their timeencountering
和右撇子进行对抗练习
and practicing against righties.
所以当二者面对彼此时
So when the two face each other,
左撇子防备右撇子对手的准备会更加充分
the left-hander will be better prepared against this right-handed opponent,
而右撇子就会被淘汰
while the righty will be thrown off.
在这个搏斗假设中 人口的不平衡导致
This fighting hypothesis, where an imbalance in the population results
左撇子格斗家或运动员处于优势
in an advantage for left-handed fighters or athletes,
是消极频率相关选择的一个例子
is an example of negativefrequency-dependent selection.
但根据进化论的原理
But according to the principlesof evolution,
具有相对优势的群体会增长直到优势消失
groups that have a relative advantage tend to grow until that advantage disappears.
如果人们自始至终只会在人类进化中竞赛 斗争
If people were only fighting and competingthroughout human evolution,
自然选择会使得更多的
natural selection would lead to more
左撇子成为那个不断增长
lefties being the ones that made it
直到世上有更多他们的群体
until there were so many of them,
惯用左手不再是一个少见的优势
that it was no longer a rare asset.
所以在纯粹竞争的世界中
So in a purely competitive world,
50%的人口会是左撇子
50% of the populationwould be left-handed.
但人类进化是由合作和竞争共同塑造的
But human evolution has been shaped by cooperation, as well as competition.
并且合作的压力从反方向推动了惯用手的分布
And cooperative pressure pushes handedness distribution in the opposite direction.
在球手表现不取决于对手的高尔夫球运动中
In golf, where performancedoesn’t depend on the opponent,
只有4%的顶尖球手是左撇子
only 4% of top players are left-handed,
这是一个更广泛的工具共享现象的例子
an example of the wider phenomenonof tool sharing.
正如年轻有潜力的高尔夫球手能够
Just as young potential golfers can
更轻易地找到一系列的右撇子俱乐部
more easily find a set of right-handed clubs,
许多影响社会的重要工具
many of the important instrumentsthat have shaped society
都是为多数的右撇子而设计的
were designed forthe right-handed majority.
因为左撇子使用这些工具时表现更糟
Because lefties are worseat using these tools,
发生事故的几率也更高
and suffer from higher accident rates,
他们在纯粹合作的世界里很少一帆风顺
they would be less successfulin a purely cooperative world,
最终就从人群中消失了
eventually disappearingfrom the population.
所以 通过正确预测
So by correctly predicting the distribution
普通群体中左撇子的分布
of left-handed people in the general population,
并匹配来自各种运动的数据
as well as matching datafrom various sports,
该模型指出存留的
the model indicates that the persistence
左撇子作为一个很小但稳定的少数群体
of lefties as a small but stable minority
反映了在竞争与合作的共同影响下
reflects an equilibrium that comes from competitiveand cooperative effects
随时间发展所达到的平衡
playing out simultaneously over time.
最有趣的是 数字能告诉我们
And the most intriguing thing is what the
关于各种群体的信息
numbers can tell us about various populations.
从合作动物中惯用爪子的不对称分布
From the skewed distribution of pawednessin cooperative animals,
到竞争激烈的狩猎采集社会中
to the slightly largerpercentage of lefties
左撇子的稍高比例
in competitive hunter-gatherer societies,
我们甚至能发现
we may even find
一些对早期人类进化的疑惑的答案
that the answers to some puzzles of early human evolution
早已在我们手中
are already in our hands.

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左撇子存在的原因

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视频来源

https://www.youtube.com/watch?v=TGLYcYCm2FM

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