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.
羽毛是动物身上几件 最奇妙的东西之一 羽毛构造极为复杂,让人惊叹 还有精细的结构 而且还够强壮 好让鸟类飞上数千尺的高空 就像其它自然界的东西一样 羽毛耗费了几百万年 进化到现在的形式 我们可能很难想像 这是怎么发生的 究竟,中间那 过度的形式是什么样子的呢? 这种在翅膀上 覆盖了羽毛的结构究竟好在哪里呢? 科学研究发现 鸟类就像是还活着的恐龙 你可以看到它们骨架非常相似 某些恐龙和鸟类一样,都有一些在动物界独一无二的身体结构 比如说叉骨(wish bones) 之后在 1990 年代末期 古生物学家开始挖掘出 一些有力的证据: 有些恐龙身上 仍旧保有羽毛 在那之后,科学家发现 许多种类的恐龙 身上都有部份羽毛 有些恐龙像鸽子一样小 有些则跟校车一样大 如果你观察一下 它们在族谱上的关系 那么要进化出羽毛 并不是那么不可能 鸟类最早的 有羽毛的祖先 是一种像电线一般的 直条羽毛 后来这些电线开始分叉 产生比较小的分支 在许多恐龙的世系中 这些简单的羽毛 进化成更加复杂的样子 包括许多我们今日 在鸟类身上看到的那种羽毛 同时 羽毛也开始 遍布恐龙的全身 从零散的小块细毛 演变为浓密的全身羽毛 甚至还长到脚上 少数的化石甚至 保存了一些 让羽毛显现出不同颜色 的分子 透过这些分子,我们发现 恐龙羽毛有着一系列漂亮的颜色: 光亮、深色的羽毛, 像是乌鸦 或是黑白相间的条纹 还有亮红色的色斑 有些恐龙头上有 高高的冠羽 而有的则是 相当长的尾羽 但是,这些恐龙 没有一只能够靠羽毛飞翔 它们的胳臂太短 而身体其它部份又太重 但是鸟类的羽毛除了让它们飞翔之外 还有其他用处。 鹬鸟用羽毛把自己隐藏于 树丛的背景中 驼鸟会伸出它的翅膀盖住巢 来保护它的幼鸟 孔雀用它华丽的尾羽 来吸引异性 羽毛在恐龙身上也可能 有这些功能 然而有羽毛的恐龙 是如何开始飞翔 仍然还是个谜 但是如果羽毛细小的恐龙 在爬坡时挥动它的臂膀 那羽毛还是可以提供一些 向上的力量 这让它跑得更快 这项物理的意外收获 可能导致 进化出更长的臂膀和羽毛 这会让牠们跑得更快 甚至可以跳跃置空一小段 最后,它们的臂膀 进化成翅膀 只有到这时候,大约是第一只 有羽毛的恐龙 出现的五千万年后 羽毛才让恐龙在天空翱翔