Scientists have found fossils of animals with tails dating back hundreds of millions of years. Back then， early fish used their tails as fins to swim through oceans， and avoid enemies. As these fish developed into creatures that lived on the land， their tails started to change too.

Scientists believe that dinosaurs swung their tails side to side to balance their heavy heads and bodies while walking on two legs. This movement allowed them to run fast enough to catch their prey. Similarly， present-day kangaroos use their tails for balance. But their tail isnt just for balance—it also works as a powerful third leg that can help push them forward through the air. In addition， a monkeys tail can also act like a hand， allowing it to hold onto tree branches.

科學(xué)家們發(fā)現(xiàn)的有尾巴的動(dòng)物化石，其歷史可以追溯到數(shù)億年前。那時(shí)，早期的魚類用尾巴作為鰭在海洋中游動(dòng)和躲避天敵。隨著這些魚進(jìn)化成為生活在陸地上的生物，它們的尾巴也開始發(fā)生變化。

科學(xué)家們認(rèn)為，恐龍用兩條腿走路時(shí)，尾巴左右擺動(dòng)，是為了平衡沉重的頭部和身體。這種動(dòng)作使它們?cè)谧ゲ东C物時(shí)能夠跑得足夠快。與之類似的是，現(xiàn)在的袋鼠也用尾巴來(lái)保持平衡。但它們的尾巴不僅僅是用來(lái)保持平衡——它還可以作為有力的第三條腿，幫助它們騰空前行。此外，猴子的尾巴也可以像手一樣，讓它能夠抓住樹枝。

Many insects also have tails. But their roles are quite different. Most tailed insects use their tails to lay eggs.

Birds use their tails both to balance while sitting on trees and to control directions and reduce drag while flying. Some birds also use their tails for mating. Take peacocks for example. Male ones will spread their colorful tails to attract female ones.

Besides， animals that live in groups， like wolves， use different tail positions to show their rank.

Although humans dont have tails like monkeys， our ancestors did have tails. Scientists believe those tails disappeared from our human ancestors around 20 million years ago. Once they started walking upright， they no longer needed tails to help with balance.

許多昆蟲也有尾巴，但它們的作用卻截然不同。大多數(shù)有尾昆蟲用尾巴產(chǎn)卵。

鳥類在樹上時(shí)用尾巴保持平衡，在飛行時(shí)用尾巴控制方向和減少阻力。有些鳥類也用尾巴來(lái)求偶。以孔雀為例，雄孔雀會(huì)展開它們多彩的尾巴來(lái)吸引雌孔雀。

此外，群居動(dòng)物，比如狼，它們的尾巴放在不同的位置就表示不同的等級(jí)。

雖然人類不像猴子那樣有尾巴，但我們的祖先確實(shí)有尾巴?？茖W(xué)家們認(rèn)為，大約在2 000萬(wàn)年前，我們的人類祖先身上的尾巴就消失了。一旦開始直立行走，他們就不再需要尾巴來(lái)幫助保持平衡。

Word Bank

prey /pre?/ n. 獵物

drag /dr?ɡ/ n. 空氣阻力

attract /?'tr?kt/ v. 吸引

What first attracted me to her was her sense of humor.