Dogs’tails are used for communicating4 with both humans and other dogs.But why did dogs start wagging their tails？ Dogs came from wolves5， but they aredifferent in color and body size， as well as behavior6. Even from a young age， dogswag their tails more than wolves do.

In past studies， dog pups7 would often start to wag their tails for the personwho cared for them by their fourth or fifth week of life. But wolf pups， which werealso raised8 by humans， almost never wagged their tails.

Other studies found that dogs don’t wag them only when they are happy. Theywag their tails more on the right side when they feel happy， and more on the leftwhen they feel sad. And they wag them most when with their owners. Whenanimals are raised by human， some features9 are passed down because humanschoose to keep those features， or because the features help those animals liveamong us.

Studies also found that humans enjoy rhythm10. This might make us like tailwaggingdogs just because we liked the rhythm. It might even explain why dogswag their tails so much when they’re around us.

Future studies will look at types of tail wagging in different situations， alongwith things like heart rate and chemicals in the brain. It is to help us learn howwagging works， and why it began.

狗用尾巴來(lái)與人類和其它狗交流。但是狗為什么開始搖尾巴呢？狗由狼進(jìn)化而來(lái)，但它們?cè)陬伾腕w型以及行為上都有所不同。即使從很小的時(shí)候開始，狗搖尾巴的次數(shù)就比狼多。

在過(guò)去的研究中，小狗在出生后的第四周或第五周經(jīng)常會(huì)對(duì)照顧它們的人搖尾巴。但是同樣由人類飼養(yǎng)的狼崽幾乎從不搖尾巴。

其他研究發(fā)現(xiàn)，狗不只在開心的時(shí)候搖尾巴。當(dāng)它們感到高興時(shí)，尾巴更多地向右側(cè)擺動(dòng)，而在悲傷時(shí)，尾巴更多地向左側(cè)擺動(dòng)。和主人在一起時(shí)，它們最喜歡搖尾巴。當(dāng)動(dòng)物被人類飼養(yǎng)時(shí)，一些特征會(huì)被遺傳下來(lái)，這是因?yàn)槿祟愑幸獗Ａ暨@些特征，或者因?yàn)檫@些特征有助于那些動(dòng)物生活在我們中間。

研究還發(fā)現(xiàn)，人類喜歡有節(jié)奏的事物。這可能會(huì)讓我們喜歡搖尾巴的狗，只是因?yàn)槲覀兿矚g這種節(jié)奏。這甚至可以解釋為什么狗在我們身邊時(shí)會(huì)不停地?fù)u尾巴。

未來(lái)的研究將著眼于在不同情況下?lián)u尾的類型，或伴隨著例如心率變化和大腦產(chǎn)生的化學(xué)物質(zhì)，以幫助我們了解搖尾巴是怎么回事以及為什么會(huì)出現(xiàn)搖尾這種行為。

（英語(yǔ)原文選自：engoo.id）