Why do we have crooked teeth when our ancestors didn’t? - G. Richard Scott

翻译人员: Sophia Ye 校对人员: Gia Hwang

All these ancient skulls have perfectly straight teeth,

这些古代头骨的牙齿都非常整齐，

despite almost certainly never sporting braces.

尽管几乎肯定从未戴过牙套，

And this isn't some strange sample.

而且这些样本并非个例。

According to the fossil record,

根据化石记录，

ancient humans usually had straight teeth,

古人类的牙齿通常比较整齐，

complete with third molars— or wisdom teeth.

包括第三臼齿，也就是智齿。

In fact, the dental dilemmas that fuel the demand for braces

事实上，如今助长牙套 和智齿拔除需求的牙科难题

and wisdom teeth extractions today appear to be recent developments.

似乎是近代的发展，

So what happened?

到底发生了什么？

While it’s nearly impossible to know for sure,

虽然几乎不可能确定，

scientists have a hypothesis.

但科学家们提出一个假设。

A couple million years ago,

大约数百万年前，

the ancestors of modern humans lived a subsistence lifestyle.

现代人祖先的生活方式是自给自足，

Their teeth and jaws had to work hard to make the food they ate digestible.

其牙齿和颌骨必须努力工作， 才能使所吃食物更容易消化。

Indeed, the surfaces of many of their teeth show extensive wear and flattening.

的确，他们许多牙齿表面 显示出严重磨损和变平，

They also had larger jaws and teeth overall.

颌骨和牙齿整体上也更大。

At some point, they began using tools and fire to cook and prepare food,

在某个时期，他们开始使用工具 和火来烹饪和准备食物，

which helped break it down.

这有助于分解食物。

A lot more time passed and, around 12,000 years ago,

随着时间推移，大约 1.2 万年前，

some humans started farming and domesticating animals and plants.

一些人类开始耕作和驯化动植物。

Over the course of several thousand years,

在几千年的时间里，

it became more common for people to process and refine their food.

人们加工和精制食物变得越来越普遍，

Milling technologies helped remove the tougher parts of grains,

粉碎技术有助去除谷物中较坚硬部分， 如大米和小麦中的胚芽和麸皮。

like the germ and bran from rice and wheat.

Fast forward to the industrial Revolution,

到了工业革命时期，

and technological innovations dramatically accelerated these processes.

技术创新极大地加快了这些过程。

In a relatively short time,

在相对较短的时间内，

many human mouths were relieved of a great deal

许多人的嘴从大量的研磨、

of their grinding, crushing, and pulverizing duties.

压碎和粉碎的任务中解脱出来。

And interestingly, it was around this time

而有趣的是，就在这个时候，

that tooth crookedness appears to have become more common.

牙齿的歪斜似乎变得更常见。

Examining fossils spanning millions of years of evolution,

研究人员通过研究跨越 数百万年进化的化石，

researchers have observed a gradual decrease in tooth and jaw size

观察到人类及其祖先的牙齿和颌骨尺寸

in humans and our ancestors.

逐渐减小的趋势。

Many think that, for most of human history,

许多人认为，人类历史的大部分时间里，

dietary shifts— like the introduction of meat and the advent of cooking—

膳食变化，如肉类的引入和烹饪的出现，

were gradual,

是逐渐发生的，

and that changes in tooth and jaw size basically kept pace with one another.

并且牙齿和颌骨尺寸的变化 基本上与之相适应。

But with the more recent revolutions in agricultural and culinary habits,

但随着农业和烹饪习惯的更近期革命，

that relationship changed.

这种关系发生了变化。

As the theory goes, over a relatively short period,

根据该理论，在相对较短的时间内，

some human populations saw a decrease in jawbone size,

一些人类群体的颌骨尺寸减小，

while teeth stayed roughly the same size,

而牙齿尺寸基本没变，

meaning they're left vying for limited space.

意味着它们要争夺有限的空间。

When they do grow in, they may displace others

当它们长出来时，

可能会造成其他牙齿移位， 并被挤到一些奇怪位置。

and get jostled into some eccentric positions.

And then wisdom teeth, which are usually the last to make their debut,

而通常最后露面的智齿

seem to only complicate things further.

似乎只会让情况更复杂。

In many cases, they have little or no space to emerge.

许多情况下，它们几乎没有生长空间，

This can lead to impacted wisdom teeth,

这可能导致阻生智齿，

which may cause discomfort and infections if not surgically removed.

如果不通过手术拔除， 可能会引起不适和感染。

So larger jaws appear to be associated with greater chewing demands.

因此，较大的颌骨似乎 与更大的咀嚼需求有关。

And many scientists think that as people's diets have become less chewy,

许多科学家认为， 随着人们的饮食越来越容易咀嚼，

their jaws have gotten smaller— and that this has led to dental crowding,

颌骨则越变越小而导致牙齿拥挤，

resulting in dental crookedness and impacted wisdom teeth.

进而导致牙齿歪斜和阻生智齿。

This hypothesis has been supported by some preliminary experimental data.

一些初步的实验数据也支持这个假设。

In a 1983 study, researchers raised 43 squirrel monkeys

在一项 1983 年的研究中， 研究人员将 43 只松鼠猴

on diets of either naturally tough or artificially soft food.

分别喂养天然坚硬食物或人工软食物。

Those fed softer food had more crowded premolars,

吃较软食物的松鼠猴前磨牙更挤，

rotated or displaced teeth, and narrower dental arches.

牙齿扭转或移位，而且牙弓较窄。

And a 2004 study similarly observed that hyraxes raised on cooked foods

2004 年的一项研究也观察到， 与吃生干粮的蹄兔相比，

experienced roughly 10% less growth in facial areas involved in chewing

吃熟食的蹄兔面部咀嚼部位的生长速度

compared to those given raw and dried foods.

约降低了 10%，

In other words, the issue at large seems to be environmental—

换句话说，整体问题 似乎是环境或生活方式问题，

or one of lifestyle— instead of a genetic one,

而非遗传问题，

though heritable factors may be at play in some instances.

尽管在某些情况下可能 存在遗传因素的作用。

It’s estimated that somewhere between 30 to 60% of people today

据估计，今天约有 30%～60% 的人口

experience some level of tooth crowding.

存在不同程度的牙齿拥挤问题。

But this trend varies across global populations.

但这一趋势在全球人口中存在差异。

Some people naturally never have wisdom teeth.

有些人天生就没有智齿，

And some don’t experience tooth crowding or crookedness

有些人不会出现牙齿拥挤或歪斜的问题，

and still get their wisdom teeth without a hitch.

仍可以顺利长出智齿。

This seems to coincide with diets that are less processed.

这似乎与较少加工的饮食相吻合，

So how can we prevent tooth crowding early,

那如何通过生活方式改变和矫正牙齿

using lifestyle changes and orthodontics?

来早期预防牙齿拥挤呢?

Well, it’s certainly something to chew over.

这确实是一件值得深思的事情。