经济学人53:羽毛化石 并非鸟类独有

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　　科技

　　Fossil feathers

　　羽毛化石

　　Not just for the birds

　　并非鸟类独有

　　A trove¹ of fossils sheds light on the evolution of feathers

　　珍贵羽毛化石的发现能够更好地阐释羽毛的进化过程

　　THE fossil record is, famously, full of holes.

　　众所周知，化石记录总是漏洞百出。

　　One such lacuna has been the absence of well-preserved feathers from the Cretaceous-the period between 145m and 65m years ago that ended with the mass extinction² that wiped out the dinosaurs³.

　　一个漏洞就是由于人们无法找到白垩纪时期保存完好的羽毛，因而该时期羽毛化石的记录一直处于空白状态。白垩纪是距今1.45亿年到6500万年的一段时期，末期发生了导致恐龙消失的物种大灭绝。

　　Now, this gap has been partly filled.

　　如今，这段空白得到了部分填充。

　　In this week's Science, a team led by Ryan McKellar from the University of Alberta report the discovery of eleven feathers preserved in amber⁴ from the latter part of the Cretaceous, about 70m-85m years ago.

　　本周，瑞安?麦凯乐领导的研究小组在《科学》杂志上发表报告称，他们发现了11种白垩纪后期（距今约7000至8500万年）封存在琥珀里的羽毛。

　　Intriguingly⁵, not all of them seem to come from birds.

　　有趣的是，这些羽毛并不都属于鸟类。

　　The origin of feathers is a mystery.

　　羽毛的起源一直是个谜。

　　The earliest known bird, Archaeopteryx, lived during the Jurassic, the period before the Cretaceous.

　　人类所熟知的最古老鸟类始祖鸟生活在白垩纪时期之前的侏罗纪时期。

　　But fossils from China suggest the precursors⁶ of feathers-simple, filament-like structures possibly used for insulation⁷-evolved in land-lubbing dinosaurs and were only later adapted for flight.

　　中国出土的化石表明羽毛的前身呈简易的丝状结构，可能具有隔离热量的功用，这些简易丝状羽毛在陆地恐龙身上不断进化，直至后来才具备了飞行功能。

　　The top picture shows similar filaments⁸ discovered by Dr McKellar and his team, suggesting flightless dinosaurs sporting such protofeathers were still around in the late Cretaceous.

　　上图所示为麦凯乐博士及其研究小组发现的类似丝状的羽毛，表明长有这些原生羽毛的“非鸟”恐龙在白垩纪后期仍然存活着。

　　Not all the feathers found by Dr McKellar were so primitive⁹, though.

　　不过，McKellar博士发现的羽毛并不都是远古时代的。

　　The second picture shows one similar in shape to those sported by modern birds.

　　第二幅图显示的羽毛形状与现代鸟类羽毛相似。

　　Modern feathers consist of thousands of fibres held together by tiny hooks.

　　现代鸟类羽毛由成千上万束靠细钩聚拢在一起的纤维构成。

　　The details of that design can be tweaked to change a feather's characteristics, offering waterproofing¹⁰, insulation, streamlining and so on.

　　通过改进羽毛构造的细节可改变它的特性，如防水、隔热、流线造型等功能。

　　The third picture shows feathers that have just such a specialisation: coiling reminiscent of that seen in the feathers of modern divers¹¹.

　　第三幅图显示的羽毛就具备这样的特殊功能：螺旋造型与现代潜鸟的羽毛相似。

　　Such coiling allows a feather to absorb water, which streamlines¹² and insulates the owner.

　　这种螺旋形状的羽毛能够吸水，并使该鸟类身形更加精巧同时起保温作用。

　　These feathers, then, presumably adorned¹³ a diving bird-perhaps Hesperornis, a flightless North American diver from precisely¹⁴ this period.

　　这些羽毛想必当时是归潜鸟所有——也许是“黄昏鸟”，一种恰好生活在这一时期不会飞翔的北美潜鸟。

　　The final picture shows pigmentation preserved in a fossil feather.

　　最后一幅图显示了封存在羽毛化石里的色素沉着。

　　Different feathers have different patterns of colour, suggesting that Cretaceous dinosaurs-flying or otherwise-used their feathers for display.

　　不同的羽毛有不同的颜色样式，这表明白垩纪时期的会飞恐龙和陆地恐龙都利用羽毛来炫示自己。

　　Charles Darwin once said that contemplating¹⁵ a peacock's tail made him sick, such was the difficulty of explaining its complexity¹⁶.

　　查尔斯?达尔文曾说过研究孔雀尾让他有头晕的感觉，可见想解释清楚其复杂性有多难了。

　　Dr McKellar's finds suggest, at least, that that complexity began to evolve a long time ago.

　　不过，麦凯乐博士的发现至少表明这种复杂性在很久以前就开始进化了。

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