Feathers are some of the most remarkable things ever made by an animal. They are gorgeous in their complexity, delicate in their construction, and yet strong enough to hold a bird thousands of feet in the air. Like all things in nature, feathers evolved over millions of years into their modern form. It could be hard to imagine how this could have happened. After all, what did the intermediate forms look like? What good is half a wing, festooned with half-feathers? Thanks to science, we now know that birds are living dinosaurs. You can see the kinship in their skeletons. Certain dinosaurs share some anatomical details with birds found in no other animals, such as wish bones. And in the late 1990s, paleontologists started digging up some compelling support for that idea: dinosaurs with bits of feathers still preserved on their bodies. Since then, scientists have found dozens of species of dinosaurs with remnants of feathers. Some were as small as pigeons, and some were the size of a school bus. If you look at how they are related on a family tree, the evolution of feathers doesn't seem quite so impossible. The most distant feathered relatives of birds had straight feathers that looked like wires. Then these wires split apart, producing simple branches. In many dinosaur lineages, these simple feathers evolved into more intricate ones, including some that we see today on birds. At the same time, the feathers spread across the bodies of dinosaurs, turning from sparse patches of fuzz into dense plumage, which even extended down to their legs. A few fossils even preserved some of the molecules that give feathers color. They reveal a beautiful range of colors: glossy, dark plumage, reminiscent of crows, alternating strips of black and white, or splashes of bright red. Some dinosaurs had high crests on their heads, and others had long, dramatic tail feathers. Now, none of these dinosaurs could use their feathers to fly - their arms were too short and the rest of their bodies were far too heavy. But, birds don't just use feathers to fly. A woodcock uses feathers to blend in perfectly with its forest backdrop. An ostrich stretches its wings over its nest to shade its young. A peacock displays its magnificent tail feathers to attract peahens. Feathers could have served these functions for dinosaurs too. Exactly how feathered dinosaurs took flight is still a bit of a mystery. But if a small-feathered dinosaur flapped its arms as it ran up an incline, its feathers would have provided extra lift to help it run faster. This accident of physics might have led to the evolution of longer dinosaur arms, which would let them run faster and even leap short distances through the air. Eventually, their arms stretched out into wings. Only then, perhaps 50 million years after the first wiry feathers evolved, did feathers lift those dinosaurs into the sky.
羽毛是動物身上幾件 最奇妙的東西之一 羽毛有華麗的交錯樣式 還有精細的結構 而且還夠強健 好讓鳥類飛上高空 就像其它自然界的東西一樣 羽毛花了幾百萬年 演化到現在的形式 可能很難想像 這是怎麼發生的 究竟,中間那 過度的形式是什麼樣子? 有半演化的翅膀 還有半演化的羽毛 好處是什麼? 由於科學的演進 我們現在知道 鳥類就像是還活著的恐龍 你可以看到牠們骨骼 類似的地方 某些恐龍在身體結構上 和鳥類是一樣的 而且在動物界是獨一無二的, 比如說叉骨(wish bones) 之後在 1990 年代末期 古生物學家開始挖掘 一些有力的證據 身上保有羽毛的恐龍 身上保有羽毛的恐龍 在那之後,科學家發現 許多種類的恐龍 身上都有部份的羽毛 有些像鴿子一樣小 有些則跟校車一樣大 如果你觀察一下 牠們在族譜上的關係 那要演化出羽毛 並不是那麼不可能 鳥類最早的 有羽毛的祖先 是有像電線般 直條的羽毛 後來這些電線開始分叉 產生比較小的分支 在許多恐龍的世系中 這些簡單的羽毛 演化成複雜的樣子 包含有些我們今日 在鳥類身上看到的那樣 同時 羽毛也開始 遍佈恐龍的全身 從零散的小塊細毛 變成濃密的全身羽毛 甚至還長到腳上 少數的化石甚至 保存了一些 造成羽毛有不同顏色 的分子 這些分子透露了 一系列漂亮的顏色 光亮、深色的羽毛, 像是烏鴉 或是黑白相間的條紋 還有亮紅色的色斑 有些恐龍頭上有 高高的冠羽 而有的則是 又長又戲劇化的尾羽 但是,這些恐龍 沒有一隻能夠 靠羽毛飛翔── 牠們的胳臂太短 而身體其它部份又太重 但是鳥類的羽毛 並不只用來飛翔 鷸鳥用羽毛把自己隱藏 在樹叢的背景中 駝鳥會伸出牠的翅膀蓋住巢 來保護牠的幼鳥 孔雀用牠那華麗的尾羽 來吸引異性 羽毛在恐龍身上也可能 有這些功能 然而有羽毛的恐龍 是如何開始飛翔 還是個謎 但是如果羽毛細小的恐龍 在爬坡時揮動牠的臂膀 那羽毛還是可以提供一些 向上的力量 這讓牠跑得更快 這項物理的意外收獲 可能導致 演化出更長的臂膀和羽毛 這會讓牠們跑得更快 甚至可以跳躍置空一小段 最後,他們的臂膀 演化成翅膀 只有到這時候,大約是第一隻 有羽毛的恐龍 出現的五千萬年後 羽毛才讓恐龍在天空翱翔