經過漫長的進化過程，人類的頭髮留下來了，對於頭髮，我們也許會說出它的幾個用途。但對於眉毛，它到底是用來幹什麼的，好多人或許會感到異常困惑。
Eyebrows have become an obsession of late, tattooed or microbladed, shaped and drawn in bold dark lines, making a statement far beyond braiding or waxing.
近來，人們似乎對自己的眉毛痴迷有加，又是紋眉，又是剃眉，或是修眉，然後畫上顯眼的深色線條，步驟遠遠超過了編發或打蠟。
Lifting one and not the other often signals disbelief, amusement, curiosity. Raising both can suggest surprise or dismay. But it wasn’t always that way.
一個人只揚起一條眉毛，往往表示懷疑、逗趣或好奇，揚起兩條眉毛則表示驚訝或沮喪。但也不一定都是這樣。
Early humans had thick, bony brow ridges that were far less nimble than ours, incapable of expressing much of anything beyond, 「Don’t mess with me, Thag.」
早期的人類有著厚厚的、骨感的眉脊，遠不如我們的靈活，無法表達出很多意思，除了「你這鳥人，別惹我。」
Scientists have long thought those brows served some structural purpose, like support for chewing prehistoric food. That they could also be used to signal aggression or intimidate competitors was largely dismissed as an evolutionary perk, as were the more flamboyant brows of modern humans.
長期以來，科學家們一直認為，從身體結構的角度講，眉毛有一定的作用，比如有助於咀嚼那個時候的食物（史前的）。它們也可能被用來表達敵對情緒或恐嚇競爭對手——這些也基本上被認為是進化上的好處，就像現代人更豔麗的眉毛。
But when Ricardo Miguel Godinho, an evolutionary anthropologist at the University of York, made digital recreations of a skull believed to be 300,000 to 125,000 years old, he found no evidence that its brow ridges provided any of the practical benefits suggested by earlier studies.
但是，約克大學(University of York)的進化人類學家裡卡多.米格爾.戈迪尼奧(Ricardo Miguel Godinho)對一個被認為是30萬至12.5萬年前的頭骨進行數字重建時，並沒有發現任何證據表明，眉脊提供了之前研究中提到的任何實際益處。
「He tested out the different possible explanations, and, effectively, there’s no reason for it,」 said Penny Spikins, an anthropologist who conducted the study with Dr. Godinho.
「他測試了各種可能的解釋，但實際上，找不到任何根據，」與戈迪尼奧博士一起進行這項研究的人類學家彭妮·斯皮金斯(Penny Spikins)說。
The findings, published April 9 in Nature Ecology & Evolution, suggest that the human brow has always been a primarily social tool, and that the smoother foreheads and expressive brows of modern humans may have evolved to accommodate our increasingly complex relationships.
4月9日發表在《自然生態與演化》(Nature Ecology & Evolution)雜誌上的研究結果表明，人類的眉毛一直主要是一種社交工具，現代人類的前額更平滑，眉毛更具有表現力，也許是為了適應我們日益複雜的人際關係。
「With a flatter, more vertical forehead, that whole area above the eyes becomes much more mobile, and the muscles can make some really subtle communicative gestures,」 Dr. Spikins said.
斯皮金斯說：「有了更平坦、更筆直的前額，眼睛上方的整個區域就變得靈活了很多，肌肉也能做出一些非常微妙的交流示意。」
And those gestures, like lifting your eyebrows to show you recognize someone, she said, 「tend to be more about expressing friendliness than intimidation.」
她表示，那些示意，比如揚起眉毛表示你認出了某人，「更多的是表示友好，而非恐嚇」。
Though such a hypothesis is difficult to test without a time machine, Dr. Spikins said it emerged from the real-life observations of Paul O』Higgins, a co-author of the study.
雖然這樣的假設在沒有時光機器的情況下很難驗證，但斯皮金斯表示，它源於這項研究的聯合作者保羅·奧伊金斯(Paul O』higgins)對真實生活的觀察。
「Paul was frustrated that his daughters spent so much time in the bathroom mirror perfecting their eyebrows, and was saying, 『What are eyebrows for?』」 she recalled. 「That’s when we thought maybe this is actually quite important.」
「保羅為女兒們花很長時間對著浴室的鏡子修眉毛感到沮喪，他說，『眉毛是幹什麼用的呢？』」她回憶道，「所以，我們當時想到，這也許是個很重要的問題。」
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