This is Scientific American's 60-second Science, I'm Christopher Intagliata.
The animal kingdom is a noisy place. There's bird song...
(CLIP: Bird whistle)
...choruses of frogs...
(CLIP: Frog chorus)
...and lots of lesser known sounds, like the ray gun–like sounds of baby alligators hatching and calling for Mom.
(CLIP: Baby alligator sound)
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.
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.
Thanks for listening for Scientific American's 60-second Science. I'm Christopher Intagliata.
“我是在十几岁的时候养的那只小短吻鳄 。有时我能听到‘呃呃呃’的声音 。它们在成长过程中会发出吼叫和‘啪啪'等各种声音 。”
“因此，我们之后所做的，就是在声通讯进化与它们是日间活跃还是夜间活跃这二者之间做统计相关性 。我们发现二者间存在非常紧密的关系 。在夜间活动的动物往往会进化出声通讯 。”
这种发声能力很可能在数亿年前独立且多次在青蛙、哺乳动物、壁虎、鸟类和鳄鱼身上产生 。虽然最早发声的可能是夜行动物，但穿山甲等夜行动物似乎已经失去了这一能力，而其它进化为日间活跃的动物，依旧保留着发声能力，当然，就像你我一样 。
谢谢大家收听科学美国人——60秒科学 。我是克里斯托弗·因塔利亚塔 。
1. grow up 长大成人；成熟；
Children grow up so fast these days.
2. all sorts of 各种各样的；形形色色的；
The new approach had wide applicability to all sorts of different problems.
3. in the first place 起初；一开始；
I should never have taken that job i n the first place.
4. at night 晚间；晚上；
These animals only come out at night.