Eyebrows Could Have Been Our Main Competitive Advantage 眉毛或是人類重要競爭優勢

施佳能

You probably already know the function of your eyebrows—they divert sweat and raindrops away from your eyes. However， they are also extremely expressive—we can guess pretty accurately what other people are feeling just by looking at their eyebrows. Now scientists from the University of York say that our eyebrows could have been a major benefit for survival.

Humans are the last surviving hominin1， Neanderthals2 are long gone. In fact， while they were slowly dying out， we were dominating the planet. And conditions were rough. So how did we manage to survive while other species came and went？ There is no simple explanation， but eyebrows might have been a key. You see， you can tell the emotion of the smiley face scribble3 on a piece of paper just by looking at his eyebrows—they are really that important. However， our ancestors did not have such expressive eyebrows. In fact， their eyebrows had little to no mobility and were characterized by a prominent bone ridge.

Scientists used 3D modelling techniques to create a digital model of the Kabwe 1 skull4. It does have a prominent eyebrow ridge， but scientists managed to shave it off5 to see what effect it would have on the mechanical performance of the bones. At it didnt have any—this ridge did not participate in distribution of biting forces. It might have been useful to protect the face （as a bumper）， but scientists argue that social functions were more important. But what kind of social functions could eyebrows have？

Now you know eyebrows are used subconsciously to express emotions. In fact， when youre pretending to be angry， you move your eyebrows down and closer together and when you are surprised， you raise them high. But eyebrows can communicate a huge variety of emotions and it was very important when humans started forming social groups. You cannot know every member of a large group， so how do you know what he is thinking and if you can trust him？ Unless you have mind reading powers， you will have to guess by facial expression.

And so mobile eyebrows could have helped humans to form social bonds which were crucial for our survival. Dr Penny Spikins， co-author of the paper， said： “While our sister species the Neanderthals were dying out， we were rapidly colonising6 the globe and surviving in extreme environments. This had a lot to do with our ability to create large social networks—we know， for example， that prehistoric modern humans7 avoided inbreeding8 and went to stay with friends in distant locations during hard times”.

It is also interesting that other studies showed that people who had botox9 injected into their foreheads and as result have less mobile eyebrows are less able to empathise and identify with10 the emotions of others. So it is better to let eyebrows be， because they might as well be our main evolutionary advantage.

你可能已經知道眉毛的功能——讓汗珠和雨滴繞道，使其不流進眼睛。然而，眉毛也極具表現力——看看別人的眉毛，就能相當準確地猜出他們的感受。英國約克大學的多位科學家稱，眉毛可能是我們生存的一大優勢。

人類是僅存的人科成員，尼安德特人早已滅絕。事實上，在他們慢慢走向滅絕的同時，我們正在占領地球。當時的環境很惡劣。那么，其他物種出現又消失的同時，我們是怎么活下來的？說來話長，但眉毛可能是一個關鍵因素。要知道，紙上隨手畫的笑臉只要瞧一眼眉毛，就能看出表達的情緒——眉毛確實非常重要。但我們的祖先并沒有這樣富有表現力的眉毛。事實上，他們的眉毛幾乎不能動，其特征是有根突出的骨脊。

科學家運用3D模型技術打造了一具名為“卡布韋1”的頭骨的數字模型。該頭骨上的確有突出的眉脊，但科學家削掉了眉脊以了解這會對頭骨其他部分的力學性能產生什么影響：結果沒有任何影響——咬合力與眉脊無關。或許眉脊有保護臉部的作用（相當于保險杠），但科學家認為，其社交功能更重要。那么，眉毛可能有什么社交功能呢？

要知道，人會下意識地用眉毛來表達情感。確切地說，假裝生氣時，人會向下皺眉;感到意外時，會揚眉。眉毛能傳遞許許多多的情感，在人類開始形成社會群體時起了非常重要的作用。在一個大群體中你不可能認識所有人，那么如何知道對方在想什么？如何知道能否信任他？除非你會讀心術，否則只能靠面部表情來猜測。

因此，靈活的眉毛可能幫助人類形成對生存至關重要的社交聯系。相關論文的合著者彭妮·斯皮金斯博士說：“我們的同類物種尼安德特人逐漸消失的同時，人類在地球上迅速聚居，在極端惡劣的環境下繼續存活。這與我們建立大型社交網絡的能力有很大關系——比如，我們知道，史前的現代智人避免同系交配，在艱難時期，會和遠方的朋友待在一起。”

同樣有趣的是，另有研究表明，因前額注射肉毒桿菌導致眉毛不靈活的一些人，他們與別人產生情感共鳴的能力較弱。因此，最好讓眉毛保持原樣，因為它們也許是我們重要的進化優勢。

（譯者為“《英語世界》杯”翻譯大賽獲獎者）