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.
Lumak dira animalia batek inoiz sortutako gauza harrigarrienetako bat. Euren konplexutasuna itzela da euren eraikuntza delikatua da eta nahiko indartsuak txori bat eusteko ehunka metro airean zehar. Naturako gauza guztien antzera lumek milioika urtetan eboluzionatu zuten gaur eguneko formara heldu arte. Zaila da imajinatzea nola gertatu izan den hau. Ze itxura zuten bitarteko formek? Zertarako balio du hego erdi batek luma erdiak dauzkana? Zientziari esker badakigu txoriak direla bizirik dirauten dinosauroak. Harreman hori eskeletoan ikus dezakezu. Zenbait dinosauroen anatomia-ezaugarriak txorienen antzekoak dira beste animalietan ez daudenak. Furkula adibidez. 1990 hamarkadaren amaieran paleontologoak ideia horren aldeko frogak ateratzen hasi ziren: luma zatien aztarnak gordetzen dituzten dinosauroak. Ordutik, zientzialariek dozenaka dinosauro espezie aurkitu dituzte lumen aztarnak dituztenak. Batzuk usoak bezain txikiak ziren eta batzuk autobus baten tamainakoak. Zuhaitz genealogikoan nola lotzen diren ikusten baduzu lumen eboluzioak ez dirudi hain ezinezkoa. Txorien ahaide lumadun urrunenak luma zuzenak zituen, kableen itxurakoak. Gero luma hauek banatu egin ziren eta adar sinpleak sortu. Dinosauro espezie askotan luma xume hauek bihurriagoak bilakatu ziren. Egun, txorietan ikusten ditugu batzuk. Aldi berean lumak dinosauroen gorputzean hedatu ziren ile-mataza eskas batzuetatik lumaje itxia egin arte hanketatik bera ere zabaldu zena. Fosil batzuk lumei kolorea ematen zioten molekulak gorde dituzte Kolore gama ederra erakusten dute: luma ilun, distiratsuak, beleak gogorarazten dituztenak txandakako zerrenda zuri-beltzak edo ukitu gorri biziak. Dinosauro batzuek buruan gandor handiak zituzten eta beste zenbaitek luma luze, dramatikoak buztanean. Baina dinosauroek ezin zituzten lumak hegan egiteko erabili. Beso laburregiak zituzten eta gainerako gorputza astunegia zen. Baina txoriek ez dituzte lumak hegan egiteko baino erabiltzen. Eperrak lumak erabiltzen ditu basoarekin guztiz nahasteko. Ostrukak habiaren gainetik zabaltzen ditu hegoak bere kumeak estaltzeko. Hegazterrenak bere buztaneko luma zoragarriak emeak erakartzeko darabiltza. Lumek zeregin hauek beteko zituzten dinosauroen kasuan ere. Lumadun dinosauroak hegan egiten nola hasi ziren oraindik misterioa da. Baina lumadun dinosauro txiki batek besoak astindu bazituen aldapan gora korrikan zebilela lumek gora bultzatuko zituen eta arinago joaten lagundu. Fisikako gertaera honek ekarriko zuen dinosauroen besoak handiago bihurtzea. Horrela, arinago egingo zuten korrika eta airean zehar salto txikiak egitea lortuko zuten. Azkenik, besoak handituko ziren hego bihurtu arte. Orduan bakarrik, behar bada 50 milioi urte igarota lehengo kable-lumak agertu zirenetik lumek, dinosauroak zeruan zehar eraman zituzten.