I am a descendent of giants.

我是巨人的後代。

With a grandfather, dad, two uncles, and an aunt all towering over 6 feet tall. Siblings and cousins, too.

有著身高皆超過 6 英尺 (183 公分) 的爺爺、爸爸、兩位伯父和一位阿姨，手足及堂 (表) 兄弟姐妹也是。

We are the people you don't want to stand behind at a Bon Jovi concert, but we're also the people who can get that thing off the top shelf for you.

我們是你在邦．喬飛演唱會上不想要站在其後的那些人，但我們也是能幫你把東西從頂層書架上拿下來的那些人。

At 6'3", I turned out to be the short one in the family.

身高六英尺三英寸 (191 公分)，我竟然是家中較矮的人。

Now that I have a son myself, I'm wondering if he's going to be tall too.

如今我有一個兒子，我在想他將來會不會也很高。

Is height only written in our genes, or is there something else that determines how tall we get?

身高基因真的寫在我們的基因裡嗎？還是有其他的因素能決定我們能長多高？

These days, the average American woman is about 5'4", while the average Joe American male is about 5'9".

當今，美國女性的平均身高為五英尺四英寸 (163 公分)，而美國男性的平均身高為五英尺九英寸 (175 公分)。

But… human height has had its ups and downs over the centuries.

但... 人類的身高數字在過去幾世紀來充滿起伏。

Three million years ago, our ancestor Australopithecus only stood about 4' tall.

300 萬年前，我們的祖先阿法南方古猿大概只有四英尺 (122 公分) 高。

One-and-a-half million years later , Homo erectus, the first early human to use complex tools, reached up to 5'7".

150 萬年後，最早使用複雜工具的直立猿人，身高達到五英尺七英吋 (170 公分)。

And by the Stone Age, men of the Gravettian hunter-gatherer culture in Europe stood at an average of 6 feet.

而到石器時代，歐洲格拉維特狩獵採集文化的男性平均身高為六英尺 (183 公分)。

Most of the historical data we have is for male height, because . . . reasons.

我們得到的大部分歷史資料都是男性的身高，因為某些... 原因。

Then agriculture happened.

接著農業時代來臨。

When Europeans switched to a lower-protein, higher-grain diet, men gradually lost 8 inches in height, on average.

當歐洲人改吃較少蛋白質、較多穀物的飲食，男性平均身高逐漸減少 8 英寸。

And they stayed that way for thousands of years.

而這個數字持續了千年之久。

By the time the 18th century rolled around, the average European man was only 5'5" inches tall.

18 世紀開始之際，歐洲男性平均身高只有五英尺五英吋 (168 公分)。

But when those Europeans emigrated to America, their kids grew up to be 5'8" inches tall on average.

然而當歐洲人移民到美國，他們的孩子平均身高長到五英尺八英寸 (177 公分)。

A huge jump in just a generation.

只隔一代竟能有如此大的成長。

During the Industrial Revolution heights took a dip due to urban crowding and disease, but soon after, the human height boom continued and continues today.

工業革命時期，身高數字小幅下滑，原因是都市人口過度集中及疾病的發生，但很快地，人類身高持續增長並延續到現在。

Every decade for the past couple centuries Europeans have grown an average of about half an inch.

過去幾世紀以來，歐洲人的身高每隔十年大約增長半英吋。

Today, Dutch men are the tallest people in the world, with an average height of just over 6 feet—back to where those Gravettians started 8 millennia ago—and, almost as tall as me.

如今，荷蘭人是世界最高的人，平均身高超過 6 英尺 (183 公分)— 這個數字又回到了格拉維特時期 8 千年前開始的身高，幾乎快跟我身高一樣高了。

These fluctuations of height, sometimes within a single generation, show that our environment determines a big part of how tall we are.

這些身高的波動，有時會在單一個世代發生，說明環境相當程度地決定了我們的身高。

But people in different regions, and different families, show us that height has genetic causes too.

但人們生活在不同地區、不同家庭，顯示出基因也是影響身高的因素之一。

So which has a bigger role, nature?

所以到底是哪個角色影響得多，大自然？

Or nurture?

還是後天養育？

In the early 19th century, scientists first noticed a correlation between people's heights and their wealth — people from poor backgrounds tended to be shorter than people who were more well-off.

在 19 世紀早期，科學家首先發現人類的身高與財富有著關聯— 貧窮家庭出身的人往往比富裕家庭出身的人矮。

Instead of asking whether someone's upbringing might influence their height, many scholars at the time decided tallness was a physical mark of "superior" humans.

許多科學家當時並沒有去探討一個人的後天養育會不會影響身高，而是認為身高高是所謂「高等」人類的身體標誌。

Francis Galton — who would later become infamous for popularizing eugenics—was the first scientist to conduct a large-scale, systematic study of height.

法蘭西斯．高爾頓 — 後來因為提倡優生學而聲名狼藉 — 是第一位對身高實施大規模且系統性研究的科學家。

He precisely measured the height of thousands of people as part of a sort of scientific side show.

他精準地測量上千人的身高數字並當成科學展示的一部份。

But Galton's results were confusing.

但高爾頓的研究結果令人困惑。

Parents' heights often didn't predict the heights of their kids.

父母的身高往往無法預測他們孩子的身高。

The heights of siblings on the other hand, were much closer.

另一方面，手足間的身高則較接近。

This inspired scientists to look at height in twins.

這個結果引發科學家針對雙胞胎的身高進行研究。

Studying twins can teach us a ton about how genes and environments influence human attributes.

研究雙胞胎可以告訴我們許多基因與環境如何影響人類特質的事物。

Fraternal twins can be as different genetically as any other pair of siblings, with the added advantage of being exactly the same age.

異卵雙胞胎可能會與另一位手足在基因上有很大的不同，但額外好處是兩位年齡皆相同。

Identical twins are genetically, well, identical.

同卵雙胞胎在基因上，是的，就是完全相同的。

So we can see how much genetic carbon copies end up differing.

所以我們可以從這些基因上相似的人中找找有多少人最後身高有所不同。

And twins separated at birth offer a window into what happens when genetically identical individuals grow up in very different environments.

還有在出生即分開的雙胞胎，可以提供我們一個了解基因上完全相同的兩個個體，成長於不同的環境會發生什麼改變的窗口。

Turns out that twins, especially identical twins, tend to be close in height—but not exactly the same.

結果是，雙胞胎，尤其是同卵雙胞胎，身高往往較接近 — 但並非完全相同。

Twin studies, like history, show us genes can only be part of the story when it comes to height.

雙胞胎研究，如同歷史給出的結論，顯示出基因僅在提到身高這個議題時佔了一部分的因素。

So, how big a part?

所以佔了多少呢？

In 2007, scientists compared height and DNA between more than 11,000 pairs of siblings and found that, across humans, 86% of height variation can be explained by genetics.

2007 年，科學家將超過 11,000 對的手足身高與 DNA 進行比較。他們發現整個人類世界， 86% 的身高變化可從基因上做解釋。

As traits go, this is very high; for comparison, genetics only explains about 26% of left-handedness.

這個數字結果其實是相當高的；相比來說，基因只能解釋大約 26% 的左撇子成因。

So we should be able to predict a person's height from his or her DNA right?

所以我們能透過一個人的 DNA 預測一個人的身高，對吧？

Well, not so fast.

沒這麼快。

We know genes make a huge difference, just not which genes.

我們知道基因會對身高產生很大的影響，但往往不知道是何種基因。

So far, scientists have identified about 800 genes that influence height, but many of them only make a tiny contribution.

至今，科學家已鑑定大約 800 個會影響身高的基因，但多數僅產生微小的貢獻。

Take HMGA2, one of the first genes linked to height.

舉 HMGA2，其中一個與身高有關的基因為例。

Having one copy of the “tall” version only “lifts” a person about an eighth of an inch, so even if you inherit a copy from both of your parents, that still only gains you a quarter of an inch at most.

得到身高「高」的一個基因遺傳只能使一個人「增長」大約 1/8 英寸，所以即使你從父母兩方得到身高「高」的基因遺傳，最多只會讓你長高 1/4 英寸。

Altogether, the 800 height genes we know of can only explain 27% of how height varies between people.

總括來說，這 800 個影響身高的基因只能解釋 27% 造成人類身高有所不同的原因。

There's clearly lots of genetic influence we don't understand.

當然還有更多我們不了解的基因會影響身高。

Maybe the effects of some genes add up in unexpected ways — genes may interact in combinations, where four and four makes sixteen, not eight.

或是有些基因效果是由意想不到的方式相加 — 基因會以合併的方式相加，4 與 4 相結合是 16，不是 8。

If we could just study the DNA of all the 7 billion people on Earth, maybe we would find all the genes that affect height.

如果我們能將地球 70 億人的 DNA 拿來研究，或許可以發現所有影響身高的基因。

Or maybe we'd find that scientists have overestimated the contribution of genetics.

也可能我們會發現科學家高估了基因對身高的貢獻度。

Because our environment, defined by health and diet, certainly has a hand in shaping our height.

我們所處環境是由健康與飲食所定義，兩者肯定在影響身高的因素中佔有一角。

South Koreans today are more than an inch taller than North Koreans, despite minimal genetic differences.

如今，南韓人的平均身高比北韓人高一英寸，儘管在基因上僅有微小差異。

Clearly, one's diet during childhood, is crucial in determining adult height.

無疑地，一個人在童年時期的飲食對於決定其成年後的身高來說相當重要。

That's why humans shrank with the switch to agriculture and again during the Industrial Revolution.

這就是為什麼人類會在轉變為農業社會時身高縮水，而在工業革命時期又開始上升。

Today, most scientists agree that nature and nurture combine to shape our height.

現今許多科學家同意大自然與後天養育的結合能型塑身高這個說法。

Some even propose calling height an “omnigenic” trait — one that nearly all our genes influence in some way.

有些人甚至建議將身高稱做一種「全基因」的特性 — 一種幾乎所有基因都能以某些方式被影響的基因。

For now, the only surefire way to know how tall you'll end up… is just to wait and see.

而現在，唯一可以讓你知道自己最後會長多高的可靠方式是... 等等看。

Stay curious!

永保好奇！

Hey guys, I want to take a second to tell you about "REINVENTORS". It's a new show from PBS Digital Studios and KCTS 9 in Seattle.

嗨各位，我想花點時間跟各位介紹 REINVENTORS。這是 PBS Digital Studios 以及西雅圖 KCTS 9 合開的新節目。

We'll introduce you to the scientists and tinkerers in the specific North West make cutting edge of green technology.

我們會介紹一些科學家以及喜歡做小發明的人，尤其在西北地區，在綠色科技方面創造先鋒的這群人。

They'll try edible plastic, so you don't have to. And bring you to unexpected places like a garage in Seattle with a nuclear reactor in it.

他們會試吃可食用塑膠袋，所以你不需親自嘗試。他們還會帶你參觀出乎意料的地方，像是在西雅圖一個放有核反應爐的車庫。

You can check out REINVENTORS and subscribe to them at the link in the description.

你可以點擊下方說明欄的連結看看 REINVENTORS 這個節目。