Why do we drive on a parkway and park on a driveway?

為什麼我們在停車道上開車 (譯註：英文 parkway 指的是大公路)，在開車道上停車？ (譯註： driveway 指的是私人車道)

Why does my hair get frizzy when it's humid?

為什麼天氣潮濕的時候頭髮會變得毛燥捲曲？

And why do my fingers get all pruney when they're wet?

為什麼手指泡水的時候會變皺？

Often we simply can't know the answers to these questions.

很多時候我們並不知道這些問題的答案。

But progress can often be made, and, when it comes to your pruney fingers, scientists have a few interesting ideas.

不過還是有些進展，在手指變皺這方面，科學家有些有趣的想法。

The story here begins with an observation made in the 1930s in the emergency room.

這要從 1930 年代時，一項在急診室裡觀察到的現象說起。

Doctors noticed that patients with nerve damage to their hands did not get pruney fingertips like most of us do in a bath, which might make you wonder, "Why would primates want wrinkly fingers, presumably when it's rainy or dewy?"

當時的醫生發現，手部神經受損的病人並不會像我們洗澡時一樣手指前端變皺，這可能會讓你好奇：「為什麼靈長類在雨天或潮濕時，會需要有皺摺的手指？」

What could this trait be for?

這項生物特徵的用處是什麼？

What if these wrinkles functioned like rain treads?

會不會手指皺摺的功能和輪胎凹槽一樣呢？

Think about car tires.

想想看車子的輪胎。

When the ground is dry, it's generally best to have smooth tires, and race cars do.

當路面是乾的時候，最好是用平滑的胎面，就像賽車那樣。

Smooth tires means more rubber or surface area in contact with the road, which gives them better grip.

平滑胎意味著會有更多的橡膠，或稱表面積，和路面接觸，這會增加抓地力。

But in rainy and muddy conditions, it's a different story, and here's where treads come into play.

但是在雨天或泥地裡，這又是另外一回事，也就是輪胎凹槽派上用場的時候了。

Treads reduce the amount of rubber on the road, but they help channelout water when it rains, lowering the risk of hydroplaning.

凹槽可會減少橡膠和路面接觸的面積，而在雨天時幫助排出雨水、降低水面打滑的風險。

Well, if your fingers really are like rain treads, you should be able to predict the optimal shape for them, right?

嗯，如果手指真的就像輪胎凹槽那樣，你應該猜得出它們效果最佳時的樣子，對吧？

So, what would the predicted wrinkle shapes be?

那麼，意料中的皺摺應該是什麼樣子？

That is, are our prunesactually the right shape to be rain treads?

也就是，我們手指的皺摺真的就像輪胎凹槽那樣嗎？

Let's take a detour into rivers.

讓我們到河裡去瞧瞧。

When we think of river networks, we usually imagine lots of smaller river channels joining to make larger river channels downstream, which is what happens in concave basins.

當想到河流網絡的時候，我們通常會想到許多較小的河道，匯聚在一起形成較大的下游河道，在向下凹的流域裡的確是這樣的。

In these cases, the divides, the regions between the river segments, are disconnected from one another and diverge away from one another uphill.

在這情況下，分水嶺——也就是河道與河道間的區域——形成分歧，並向上分佈在地勢較高處。

But river networks look fundamentally different on convex promontories or protrusions.

但是在向上凸的海岬或隆起處，河流網絡就截然不同了。

Here, the river channels are disconnected from one another and diverge away from one another downstream, not very river-like.

在這裡，河道會被劃分開來然後分佈在各個下游區，跟平常的河流不太一樣。

In these cases, it's the divides that link together to form a tree, with its trunk uphill at the top of the promontory.

在這情況下，這些分水嶺像樹的形狀般連結在一起，隆起處頂端就是樹幹。

Here, it's the divides that look more traditionally river-like.

在這情況，反而是分水嶺比較有河流的樣子。

If our pruney fingers are drainage networks, designed to channel out water when they grip, then we expect to find similar shapes on our fingers as we find out there among rivers.

如果泡水手指上的皺摺是個排水系統，是設計來在抓取物品時引導水流，那我們可以料想得到手指皺摺會有類似河流的形狀。

There should be a tree network of divides, or ridges, with their trunk near the top of the fingertip and with their more leaky parts reaching out downhill, away from the tip.

應該會有分水嶺或山脊的樹狀網絡，而樹幹部份應該在指尖附近，各排水凹槽則自頂端向手指下方延伸。

The channels themselves, through which the water is channeled during a grip, should not connect to one another, and instead should diverge away from one another downhill.

這些在抓取物品時用來引導水流的水道，應該沒有彼此相連，而是各自向下分散。

If pruney fingers are rain treads, then they should look like the river networks on convex promontories.

如果手指皺摺是輪胎凹槽，那它們就應該看起來像是隆起處的河流網絡。

In fact, that's exactly the morphology we find among pruney fingers!

事實上，這正是我們在手指皺摺上發現的結構形態！

When we grip, then, our pruney wrinkles really do channel out the water.

當我們抓取物品時，那些李子乾狀的皺摺的確可以將水排出。

But does it actually help us grip?

但它真的對抓取物品有利嗎？

New behavioral experiments have shown that they do.

一些新的行為實驗證明了這點。

In a task where subjects had to grasp wet marbles and move them through a hole and out the other side, those with pruney fingers finished the task significantly faster than those with smooth fingers.

在一項研究中，受試者必需抓取濕的大理石，並將大理石擲到洞的另一邊，比起平滑手指的對照組，手指有皺摺的那組明顯快了許多。

Pruney fingers not only ought to enhance grip in wet conditions but do.

手指皺摺不只是「看似會」在潮濕條件下增加抓取能力，而是「真的會」。

So, pruney fingers may be a crucial part of the primate repertoire.

所以手指皺摺是靈長類的一項重要生物特徵。

Maybe, once primates lost their claws in favor of fingernails, rain treads were needed to deal with the especially challenging, often wet, grip-heavy forest habitats.

也許，在靈長類選擇指甲而失去尖爪的時候，這些凹槽在面對這種格外具挑戰、經常潮濕而且仰賴抓取力的森林棲地時，就能派上用場

By looking closely at the mysteries in our world and trying to find things that look similar, like our wet fingers and rain treads, we can come up with ideas about what's happening.

藉由深入了解我們世界的奧妙，並試著找尋類似的模式，比如說泡水的手指和輪胎凹槽，我們就會對發生的事情有一些想法。

And that's a good way to think about all sorts of questions in life, too.

這同樣也是拿來思考生活中五花八門大小事的好方法。