Why do fingers become pruney? - Mark Changizi

Transcriber: Andrea McDonough Reviewer: Jessica Ruby

翻译人员: mina wong 校对人员: Vivi Dai

There are all sorts of things

每天都会发生各种事情

that happen every day

that might make you ask,

让你产生疑问：

"Why?

为什么？

Why do we drive on a parkway

为什么我们在马路上开车

and park on a driveway?

而在停车道上停车？

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

为什么湿度大时，我的头发会变卷曲？

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

为什么我的手指在泡水以后会变皱？

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

我们通常并不知道这些问题的答案

But progress can often be made,

不过还是经常取得进展

and, when it comes to your pruney fingers,

在手指变皱这个问题上

scientists have a few interesting ideas.

科学家提出了一些有趣的设想。

The story here begins with an observation

这要从1930年

在急诊室里观察到的一个现象说起。

made in the 1930s in the emergency room.

Doctors noticed that patients

医生们发现

with nerve damage to their hands

手部神经受损的患者

did not get pruney fingertips

不会像普通人那样

like most of us do in a bath,

洗澡时手指尖变皱

which might make you wonder,

你可能会觉得好奇

"Why would primates want wrinkly fingers,

“为什么灵长类在雨天或湿度大时

presumably when it's rainy or dewy?"

手指会有褶皱呢？”

What could this trait be for?

这个生物特征有什么用处呢？

What if these wrinkles functioned like rain treads?

褶皱的功能会不会和轮胎凹槽一样呢？

Think about car tires.

想一想车轮胎

When the ground is dry,

当路面是干的时候

it's generally best to have smooth tires,

最好是用平滑的轮胎

and race cars do.

就像赛车那样

Smooth tires means more rubber

平滑的轮胎可以让橡胶或其表面

or surface area in contact with the road,

与地面有更多的接触

which gives them better grip.

这样会增加抓地力

But in rainy and muddy conditions,

然而，在下雨和泥泞的情况下

it's a different story,

这又是另一回事了

and here's where treads come into play.

这时候轮到轮胎凹槽大显身手

Treads reduce the amount of rubber on the road,

凹槽减少橡胶表面与路面的的接触面积

but they help channel out water when it rains,

但在下雨时可以帮助轮胎排水

lowering the risk of hydroplaning.

降低轮胎打滑的风险

Well, if your fingers really are like rain treads,

那么，如果手指真的像轮胎凹槽那样

you should be able to predict

你应该猜得到

the optimal shape for them, right?

它们效果最佳的样子，对吗？

So, what would the predicted wrinkle shapes be?

那么，意料中的皱褶应该是什么样子呢？

That is, are our prunes actually the right shape

也就是说，我们手指上的皱褶真的像

to be rain treads?

轮胎凹槽那样吗？

Let's take a detour into rivers.

让我们先去河里瞧瞧吧

When we think of river networks,

当我们想到河网分布时

we usually imagine lots of smaller river channels

通常会想到有许多较小的河道

joining to make larger river channels downstream,

汇聚而成相对较大的下游河道

which is what happens in concave basins.

在地形向下凹陷的流域里就是这样的

In these cases, the divides,

在这种情况下，分水岭

the regions between the river segments,

也就是让两个相邻的水域

are disconnected from one another

形成分岔

and diverge away from one another uphill.

并向上分布在地势较高处。

But river networks look fundamentally different

但是向上凸起的海岬或隆起处

on convex promontories or protrusions.

河网分布就截然不同了。

Here, the river channels are disconnected from one another

在这里，河道会被划分开来

and diverge away from one another downstream,

分布在各个下游区

not very river-like.

跟我们平常所见的河流有所不同。

In these cases, it's the divides

这种情况下的分水岭

that link together to form a tree,

像树的形状一样连在一起

with its trunk uphill at the top of the promontory.

顶端隆起的部分为树干。

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

在这里，反而是分水岭看起来像河流一样

If our pruney fingers are drainage networks,

假设我们手上的皱褶是排水系统

designed to channel out water when they grip,

设计来在抓取物品时排出水流

then we expect to find similar shapes on our fingers

那我们可以想到那些褶皱

as we find out there among rivers.

应该和河流的形状相似。

There should be a tree network of divides,

它们应该有树型的分水岭或山脊

or ridges, with their trunk near the top of the fingertip

树干部分应该接近指尖

还有更多的排水皱褶

and with their more leaky parts

reaching out downhill, away from the tip.

则自顶端向手指下方延伸。

The channels themselves,

这些在抓取物品时

through which the water is channeled during a grip,

用来引导水流的水道

should not connect to one another,

应该是不相互连接的

and instead should diverge away from one another downhill.

而是各自向下分散

If pruney fingers are rain treads,

如果手指皱褶是轮胎凹槽

then they should look like the river networks

那它们看起来应该像是

on convex promontories.

隆起处的河网

In fact, that's exactly the morphology

事实上，这正是我们

we find among pruney fingers!

在手指褶皱上发现的形态！

When we grip, then,

当我们拿起东西的时候

our pruney wrinkles really do channel out the water.

褶皱可以帮助我们排掉水分。

But does it actually help us grip?

但是，这真的有利于拿取物品吗？

New behavioral experiments have shown that they do.

新的行为实验提供了有力的证明。

In a task where subjects had to grasp wet marbles

在一项研究中，受试者必须抓取湿的大理石

and move them through a hole and out the other side,

并将其扔到洞的另一端

those with pruney fingers finished the task

手指有皱褶的受试者

significantly faster than those with smooth fingers.

明显比手指光滑的受试者更快完成任务。

Pruney fingers not only ought to enhance grip in wet conditions

手指皱褶不只是“应该会”在潮湿情况增加抓取能力

but do.

而且“确实会”。

So, pruney fingers may be a crucial part

所以，手指皱褶

是灵长类的一项重要生物特征。

of the primate repertoire.

Maybe, once primates lost their claws

也许，在灵长类抛弃爪子

in favor of fingernails,

而选择指甲时

rain treads were needed to deal

这些皱褶就派上了用处

with the especially challenging,

来应付极具挑战性的

often wet, grip-heavy forest habitats.

时常潮湿、需要强抓取力的森林栖息地。

By looking closely at the mysteries in our world

通过深入了解我们世界的奥秘

and trying to find things that look similar,

并试着找到相似形态

like our wet fingers and rain treads,

比如发皱的手指和轮胎凹槽

we can come up with ideas about what's happening.

我们可以对这些现象提出设想。

And that's a good way to think about

而且，在面对生活中的各种问题时

all sorts of questions in life, too.

这也是一种不错的思考方式。