To see if wrinkled primate fingers had similar features to river basins, Changizi and his team analysed photos of 28 human fingers. They found that wrinkled fingers had the exact inverse formation as river drainages, with a raised, interconnected “tree” of bumpy skin, punctuated by diverging, disconnected sunken channels.

为了确定灵长类手指起皱是否与江河流域有共同点，尚依兹和他的团队分析了28个人类手指的照片。他们发现起皱的手指恰好是逆向的河流排水系统，鼓起的皮肤形成了凸起的相互连通的“树状”结构，而分叉的、互不连通的、下沉的渠道加强了这一结构。

The ridges aren’t haphazardly placed; that inverted pattern actually makes sense. Rivers combine water, while the channels on a wrinkled finger and meant to force water away. “The act of pressing a fingertip down on a wet surface squeezes the fluid out from under the finger through the channels, and upon completion of this single pulsatile flow the entire finger’s skin contacts the surface,” write the researchers.

凸起的纹路是有章可循的；逆向的结构是有根据的。尽管河流将水汇聚起来，但起皱的手指上的沟渠是以排水为目的。“把指尖按压在潮湿的表面上，手指上沟壑中的水就被挤出，完成这样的一次脉动后，手指的皮肤就完全贴住表面了，”研究者写道。

And then there’s this: wrinkles don’t appear until around five minutes of constant exposure to water, meaning that incidental contact isn’t enough to result in wrinkling, the response only becomes useful in rainy or dewy conditions. And it occurs far more quickly in response to freshwater than seawater, which could reflect the circumstances in which it may have originally evolved in primates.

另外，皱纹会在持续接触水五分钟后出现。也就是说，偶然碰到水并不足以导致皮肤起皱，这种反应只在有雨水或露水的环境下才会发挥作用。而在淡水中出现这一反应的速度比在海水中快很多，这说明这一反应可能原本就是灵长类进化的结果。

Even if the wet-wrinkling response didn’t explicitly evolve to aid in gripping, it could still be that it remains useful for the task. Indeed, a 2013 study conducted by British neuroscientists uncovered evidence that wrinkled fingers aided people in manipulating wet objects.

尽管没有清晰的证据证明泡水起皱反应就是为了增强抓握力而进化出来的，但是它仍然有利于人类完成这类任务。2013年英国神经科学家发现证据，证明起皱的手指有助于人操控潮湿的物体。

In the experiment, 20 people had to transfer 45 objects of different sizes – all marbles and fishing weights – from one container into another. In some cases, the objects were dry while the participants’ fingers were either smooth or wrinkled. In other cases, the objects were submerged. They found that wrinkled fingers allowed the participants to more quickly transfer the objects when submerged, though they made no difference for dry objects.

在实验中，20个人将45个不同大小的物品——所有都是大理石和钓鱼用的沉子——从一个容器取出，放到另一个容器中。一些情况下，物品是干的，而被试者有的手指是平滑的，有的是起皱的。在另一些情况下，物品泡在水里。他们发现，起皱的手指能让被试者更快地搬运水中的物品，但是对干的物品没有作用。

However, a similar 2014 study conducted by German researchers found the opposite. In that study, the researchers had 40 people transfer 52 marbles and dice of different sizes and weights from one container into another. They found, however, no significant differences in the participants’ ability to manipulate the objects, no matter whether their fingers were smooth or wrinkled, and the objects dry or submerged.

不过，2014年德国研究者进行的一个类似的研究产生了相反的结论。在该研究中，研究者让40个人在两个容器之间搬运52枚不同大小的大理石和骰子。但是结果发现，不论手指是光滑的还是皱的，也不论物品是干的或是湿的，被试者操控这些物品的能力都没有变化。

Likewise, a group of Taiwanese researchers conducted a series of experiments aided by a 24-year-old male volunteer. They assessed the friction applied to a smooth surface by his smooth or wrinkled fingertips, for example, and how much force his hands applied when sliding across a bar. They also measured his ability to force two ends of a spring together. Rather than finding no differences, however, they actually found that wet-wrinkles resulted in decreased performance for each test.

台湾的一些研究者也有类似的发现。在一名24岁男性志愿者的帮助下，他们进行了一系列的实验。比如，他们让志愿者用光滑或起皱的手指接触一块光滑的表面，根据他的手抚摸时的力量计算摩擦力。他们还测量了志愿者挤压弹簧两端直到合拢的能力。然而，他们不仅没有发现任何变化，还发现在每项测试中起皱手指的表现较差。

Of course, if the wet-wrinkling response did evolve as an adaptation, it was certainly not for the highly contrived laboratory conditions in which these experiments were run.

当然，假如泡水起皱反应真的是适应环境进化的结果，那它当然不适用于这些精心设计的实验环境。

Changizi thinks that the wet-wrinkling response is useful for supporting one’s own body weight, not for fine-motor manipulations of small objects. “If you're really going to do a behavioural test where it matters, [it should be] gripping onto trees or heavier things, not little marbles,” he says. “You’re not at a risk of hydroplaning in any way,” he points out, when your task is to transfer marbles between buckets. The key is to assess the impact of wrinkled skin on locomotion, rather than on dexterity.

尚依兹认为泡水起皱反应有利于支撑人体的重量，但不利于对小物品的精细操作。“如果你真的打算进行行为测试，那应该测试抓住树枝或其他较重的东西，而不是小块的大理石。”他说。当说到把小块大理石从一个水桶搬到另一个水桶时，他说：“无论如何，你没有轮胎打滑那样的风险。”关键是评估皮肤起皱对运动的作用，而不是对灵敏度的作用。

His ideal experiment? Recruiting parkour experts to show off their urban acrobatics while either wrinkled or non-wrinkled, and in wet or dry conditions. “In some kind of safe way,” he adds.

他理想的实验是什么？招募跑酷达人，在潮湿和干燥的时候和在皮肤起皱和不起皱的情况下，展现他们在城市中的杂技。“以某种安全的形式。”他补充道。