SciShow recently began producing its fifth year of content.

SciShow 致力於製作影音內容已經邁入第五年

Something that we are extremely proud of.

我們為此感到非常驕傲

And we're also proud of the community that's grown up around these videos.

我們同時也為圍繞著這些影音內容所聚集的社群感到驕傲

We've covered a lot of topics, both trivial and profound,

我們目前已經談了很多主題，瑣碎的、深層的都有

and we work very hard to capture both our fascination and excitement

我們很努力地表達我們的著迷與興奮

as well as our deep desire to always get things right.

同時兼顧我們極力想把事情做好的渴望

And over the last year, you may have noticed

去年，你或許發現了

a comment on, we think, every - single - SciShow video,

一個留言，我們猜測，幾乎是我們 SciShow 的每一部影片都有一個留言

asking us one question.

問了一個問題

We have ignored this question long enough,

我們已經忽略這個問題夠久了

it is time we took it on.

現在是時候該正面迎擊了

litojonny wants to know: why does he have hair around his anus?

litojonny 想知道：為什麼他的肛門附近會有毛？

Well jonny, the reason we haven't answered you

Jonny 我們一直沒有回答你的問題

is because, you know, like despite the fact that

是因為即使到了今日，科技發達到

everyone gets their own personal pocket sized supercomputer,

每個人都擁有一台能放進口袋的超級電腦

and that we can send robots to Mars,

送機器人去火星

and convert the entire face of the planet to human use,

甚至將整個表面收歸版圖為人類所用

we still do not really know WHY humans have butt hair.

我們還是不清楚為什麼人類的屁股有毛

And it may not surprise you to learn,

你或許也不會太驚訝於

that not a whole lot of research has been done

目前並沒有大量的研究

on the "Why" part of this question about butt hair.

專注於解釋「為什麼」屁股有毛

But a fair amount of study has gone into the medical problems that butt hair can cause.

但確實有一些研究涉略到屁股毛可能造成的醫學問題

For example: Pilonidal Disease is a chronic skin infection.

舉例來說，藏毛疾病就是一種慢性皮膚感染

Caused by hairs that get embedded near the top of the butt crack,

此病就是由長在股溝上部的毛所引起

which, if you want to impress your doctor,

如果你想讓你的醫師對你影印象深刻

you can describe by its technical name: the intergluteal cleft.

你也可以用專業術語，稱那個部位為臀間溝（the intergluteal cleft）

So as the owner of a butt yourself,

擁有一個屁股的你

you probably know that butt hair does seem to have more downside than upside.

應該會知道屁股毛似乎弊多於利

So given that, what - if any - purpose does it serve?

所以既然如此，如果它有用處，那它的用處是什麼？

Well there are a few theories out there

是有一些理論可以解釋

and maybe some enterprising scientist out there, watching right now, can do some research on them.

或許也有一些具深究精神的科學家，正在收看我們的節目，你們也可以去研究一下

But here's what's been proposed.

但這裡我要講的是一些已經被提出的理論

Theory number 1: Butt hair exists, because there's just no significant evolutionary pressure against butt hair.

理論一：屁股毛存在是因為，沒有明顯的演化壓力導致這一性狀消失

Sure, it's sometimes inconvenient, and, depending on the moment in cultural history,

的確它有時滿不方便的，而且在歷史文化上

It might be considered unsightly.

它或許被認為有礙觀瞻

But it appears, that butt hair has never been a significant reason for one human not to make babies with another human.

不過，看起來屁股毛並不會是一個人類選擇不和另一個人類交配的主要理由

It's important to keep in mind, that not every bit of our physiology needs an evolutionary purpose,

記住一件重要的事：並不是我們所有的生理構造都需要有一個演化目的才能存在

so butt hair might just be another side effect of unintelligent design.

屁股毛可能只是另一個（人類）不完美設計的副產品

Theory number 2: Scent communication

理論二：氣味傳播

Body odor definitely has a negative connotation in today's world, but there's little doubt that communication through scent has played an important role in the evolution of humans.

體味在當今世界顯然不是什麼好東西；但毋庸置疑的是，氣味傳播在人類的演化進程中，扮演了重要角色

After all, that's likely why we have body hair in the same areas where we produce body odors.

畢竟，這也很可能是為什麼我們身體其他產生氣味的部位也都有毛的原因

The hair is there to hold onto sebaceous, or oily, secretions, that have their own smell,

毛髮長在那些地方，是為了抓住我們帶有氣味的油性分泌物

and are also consumed by bacteria, that create even more smells.

這些分泌物又被細菌分解，製造更多氣味

Since we all produce different smell compounds, and all have our own microbiomes,

因為我們都會分泌不同帶有氣味的化合物，而且身上的微生物群系也不同

each individual human actually smells different.

每一個人聞起來都不一樣

And if our early human ancestors were anything like other animals, and they probably were,

所以如果我們的人類祖先的行為或特質就像其他動物一樣

their personal smell probably helped with everything from broadcasting territorial rights to attracting mates.

他們的個人化氣味可能可以幫助他們宣示領土或吸引配偶

Butt hair then may be just another way our oldest human ancestors enhanced their smell profiles.

所以屁股毛可能只是另一種人類先祖用來增強體味的方法

Theory number 3: Friction.

理論三：摩擦

In addition to giving off smells, humans have also always done a great deal of walking and running.

除了散播體味，人類也從事大量跑步和走路等活動

And skin rubbing on skin (especially in areas where that skin may be moist and dirty),

導致皮膚間的摩擦，尤其是在潮濕骯髒的皮膚區塊

can cause irritation, rashes, and even serious, debilitating infection.

可能導致發炎、皮疹或衰弱感染

It's even possible, that those sebaceous or waxy secretions, that help produce body odor,

也有可能我們用來製造體味的油性和蠟狀分泌物

are held in place by body hairs to provide an added benefit, acting like a kind of natural anti-chafing cream.

被體毛抓住保留於皮膚上，作為天然的「抗擦傷藥膏」

Now this theory, of the ones that we have talked about, is most appealing to me, personally,

目前這個理論是上述理論當中最吸引我的

but it's very difficult to test, because shaving, or otherwise removing butt hair,

但非常難以測試，因為請某人把體毛刮掉或用各種方式除掉

and then having someone run 20 miles on a treadmill,

然後叫他們在跑步機上跑二十英里

is not a good experimental design.

似乎不是一個好的實驗設計

Because, there's no way to know, whether any irritation is caused by the lack of hair,

因為我們無法知道其發炎反應是由於缺乏毛髮

or whatever technique was used to remove the hair.

還是因為除毛的手續所導致

None of which sound fun to me.

兩者聽起來都不是什麼有趣的事

But I have come up with an alternative experimental design that I like quite a lot.

但我想到了另一個我很喜歡的實驗設計

Just interviewing a few hundred runners about how much they need to worry about butt chafing,

只要訪問幾百個跑者，他們有多需要擔心屁股擦傷

and then measure the density of their anal pelage, to see if there's any correlation between whether they chafe and how hirsute their buts are.

並且測量他們肛門皮毛的密度，看看擦傷和屁股毛的多寡是否有相關性

Which is not an experiment that I want to to do personally.

我個人是不太想實行這個實驗

But if there's an expert out there, in anatomy and physiology, who's up for tackling this prickly problem,

但如果有解剖學和生理學專家打算研究這個棘手的問題

please, take it on.

拜託，上吧！

And if you get any useful data, definitely let us, and litojonny, know, how it went.

如果你研究出任何有用的數據，務必讓我們，還有 litojonny 知道

Thank you for watching this episode of SciShow,

感謝大家收看這一集的 SciShow

especially to litojonny, for being so persistent...

特別感謝 litojonny，如此堅持（想要知道這個問題的答案）

Ah... What are you gonna do now?

現在你要怎麼辦？

We answered your question, you're gonna come up with a new one?

我們已經回答了你的問題，所以你要想一個新的嗎？

I challenge you,

我挑戰你

to come up with a new one.

來想一個新問題吧！

Thank you for watching

感謝收看

and if you want to go to youtube.com/SciShow and subscribe,

如果你能訂閱 youtube.com/SciShow

that would be great.

那就更棒了