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

譯者: Lilian Chiu 審譯者: Helen Chang

All these ancient skulls have perfectly straight teeth,

所有這些古老的頭骨 都有排列完美的牙齒，

despite almost certainly never sporting braces.

儘管幾乎可以確定 從來沒有做過矯正。

And this isn't some strange sample.

這並不是奇怪的特例。

According to the fossil record,

根據化石記錄，

ancient humans usually had straight teeth,

古人的牙齒通常都排列得很整齊，

complete with third molars— or wisdom teeth.

且是有第三臼齒或智齒的完整組合。

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

事實上，現今需要

and wisdom teeth extractions today appear to be recent developments.

做矯正或拔除智齒的牙齒問題

顯然是近期才發展出來的。

So what happened?

所以，發生了什麼事？

While it’s nearly impossible to know for sure,

雖然不可能百分之百肯定， 但科學家有個假設。

scientists have a hypothesis.

A couple million years ago,

數百萬年前，

the ancestors of modern humans lived a subsistence lifestyle.

現代人的祖先過著自給自足的生活。

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

他們的牙齒和下顎要很費力讓 他們的所吃的食物能被消化。

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

的確，他們許多牙齒的表面

呈現大規模的磨損和變平。

They also had larger jaws and teeth overall.

整體來說，他們的 下顎和牙齒也比較大。

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

後來，

他們開始用工具和火 來烹飪和料理食物，

which helped break it down.

讓食物容易分解。

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

又經過更長的時間， 在大約一萬兩千年前，

some humans started farming and domesticating animals and plants.

有些人開始放牧、 馴養動物，和耕種植物。

Over the course of several thousand years,

經過了七千年，

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

人類更常加工和精製食物。

Milling technologies helped remove the tougher parts of grains,

研磨技術有助於將從米和小麥中

like the germ and bran from rice and wheat.

胚芽和麩皮等較硬的部分除去。

Fast forward to the industrial Revolution,

快轉到工業革命，

and technological innovations dramatically accelerated these processes.

科技創新大大加速了這些過程。

In a relatively short time,

在相對較短的時間裡，

many human mouths were relieved of a great deal

許多人的嘴巴

不再需要做大量的磨碎、咬碎，

of their grinding, crushing, and pulverizing duties.

及粉碎的工作。

And interestingly, it was around this time

有趣的是，就在這段時期，

that tooth crookedness appears to have become more common.

咬合不正也變得更常見了。

Examining fossils spanning millions of years of evolution,

調查了橫跨數百萬年 演化的化石之後，

researchers have observed a gradual decrease in tooth and jaw size

研究者觀察到人類和我們的 祖先，都有牙齒和下顎

in humans and our ancestors.

尺寸在漸漸在變小的現象。

Many think that, for most of human history,

許多人認為，在大部分人類歷史中，

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

飲食的轉變都是漸進式的，

如肉類的引入和烹飪的出現，

were gradual,

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

而牙齒和下顎尺寸的改變，

基本上，也符合相同的步調。

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

但更近期的農業 及烹飪習慣革命出現後，

that relationship changed.

這關係不再了。

As the theory goes, over a relatively short period,

根據這個理論， 在相對較短的時間內，

some human populations saw a decrease in jawbone size,

有一些人類族群的 下顎骨尺寸變小了，

while teeth stayed roughly the same size,

但牙齒的尺寸大致上不變。

meaning they're left vying for limited space.

這意味著牙齒得要爭奪有限的空間。

When they do grow in, they may displace others

當牙齒長大時，

可能會讓其他牙齒移位， 被擠到偏離的位置。

and get jostled into some eccentric positions.

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

而通常最後才長出來的智齒

seem to only complicate things further.

似乎就會讓情況變得更複雜。

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

在許多情況下，它們都只有 一點或甚至沒有空間長出來。

This can lead to impacted wisdom teeth,

這可能會造成阻生智齒，

which may cause discomfort and infections if not surgically removed.

如果不靠手術拔除， 可能會造成不適或感染。

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

所以很顯然，下顎較大 和咀嚼需求較高有相關性。

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

許多科學家認為，

當人的飲食變得不那麼需要咀嚼，

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

他們的下顎就變小了——

這就導致牙齒擁擠，

resulting in dental crookedness and impacted wisdom teeth.

造成咬合不正以及阻生智齒。

This hypothesis has been supported by some preliminary experimental data.

這項假設已經得到一些 初步的實驗資料支持。

In a 1983 study, researchers raised 43 squirrel monkeys

在 1983 年的一項研究中，

研究者養了四十三隻松鼠猴，

on diets of either naturally tough or artificially soft food.

分別用天然堅硬的食物 或人工軟化的食物來餵養。

Those fed softer food had more crowded premolars,

吃較軟食物的松鼠猴， 前臼齒會比較擁擠，

rotated or displaced teeth, and narrower dental arches.

更多轉向或移位的牙齒，

牙弓更狹窄。

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

2004 年也有一項 類似的研究，觀察到

用烹飪過的食物養育的蹄兔

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

咀嚼相關的面部區域

成長比例少了約 10%，

compared to those given raw and dried foods.

這是相對於用生食和乾燥食物 養育的蹄兔的數字。

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

換言之，整個問題 似乎來自於環境——

or one of lifestyle— instead of a genetic one,

或生活方式——而不是基因，

though heritable factors may be at play in some instances.

不過在某些例子中， 可遺傳的因素可能也有影響。

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

據估計，現今有 30% 到 60% 的人

experience some level of tooth crowding.

有某種程度的牙齒擁擠現象，

But this trend varies across global populations.

但全球各地人口的 這項趨勢有所不同。

Some people naturally never have wisdom teeth.

有些人天生就沒有智齒，

And some don’t experience tooth crowding or crookedness

也有些人沒有牙齒擁擠 或咬合不正的狀況，

and still get their wisdom teeth without a hitch.

仍然能長出智齒且毫無問題。

This seems to coincide with diets that are less processed.

這似乎和較少加工的飲食相吻合。

So how can we prevent tooth crowding early,

所以我們要如何靠改變生活方式

using lifestyle changes and orthodontics?

和矯正牙齒來早期預防牙齒擁擠？

Well, it’s certainly something to chew over.

這個問題肯定是需要好好地思考。