The animal kingdom is a noisy place. There's bird songchoruses of frogs.and lots of lesser known sounds, like the ray gun–like sounds of baby alligators hatching and calling for Mom.
There's lots of videos of them doing this on YouTube if you're curious. "When I was a kid growing up, I had a pet alligator. It vocalized a lot." John Wiens, an evolutionary ecologist at the University of Arizona. "So I had this baby alligator when I was a teenager. Sometimes I could hear 'Urh urh urh urh.' And when they grow up, they do bellows and slaps and all sorts of sounds."
Wiens and his collaborator Zhuo Chen wondered: Why did animals start vocalizing in the first place? Well, one hypothesis was that the ability originated in nocturnal animals—cause, you know, sound works a lot better than colors or horns or other visual cues when you can't see.
動物王國是個喧鬧的地方。這裡有鳥鳴…蛙聲…還有許多鮮為人知的聲音，比如小短吻鱷被孵化和呼喚媽媽時發出的射線槍般的聲音。如果你感到好奇，YouTube網站上有許多這類視頻。
「我小時候養過短吻鱷當寵物，它總是叫。」亞利桑那大學的進化生態學家約翰·維恩斯說到。
「我是在十幾歲的時候養的那隻小短吻鱷。有時我能聽到『呃呃呃』的聲音。它們在成長過程中會發出吼叫和『啪啪'等各種聲音。」
維恩斯及其合作者卓晨想知道：動物最初發出叫聲的原因是什麼？一種假設認為，這種能力源於夜間行動物，因為在看不見的情況下，聲音比顏色、角或其他視覺提示的效果要好得多。
Wiens and Chen built an evolutionary tree of nearly 1,800 vertebrate species and mapped onto it information on whether each lived by day or night and whether they made sound.
"So one of the things we did then was to do a statistical correlation between the evolution of acoustic communication and whether they were active by day or by night. And we found a very strong relationship. Those that are active at night tend to evolve acoustic communication."
Suggesting that the nocturnal notion was more than just a shot in the dark.
The findings are in the journal Nature Communications.
This ability to vocalize likely arose independently, multiple times, hundreds of millions of years ago—in frogs, mammals, geckos, and birds and crocodilians. And though vocalization might have originated with nocturnal animals, some night dwellers seem to have lost the ability—like pangolins—while others, which evolved to be active by day, retained it—like, of course, you and me.
維恩斯和Chen為近1800種脊椎動物建立了進化樹，並標註了每種動物是日行還是夜行，以及是否發聲的信息。「因此，我們之後所做的，就是在聲通訊進化與它們是日間活躍還是夜間活躍這二者之間做統計相關性。我們發現二者間存在非常緊密的關係。在夜間活動的動物往往會進化出聲通訊。」
這表明夜行概念不僅僅是在黑暗中活動。這項研究發表在《自然·通訊》期刊上。
這種發聲能力很可能在數億年前獨立且多次在青蛙、哺乳動物、壁虎、鳥類和鱷魚身上產生。雖然最早發聲的可能是夜行動物，但穿山甲等夜行動物似乎已經失去了這一能力，而其它進化為日間活躍的動物，依舊保留著發聲能力，當然，就像你我一樣。