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.
Perje spada u najčudesnije pojave u životinjskom svijetu. Predivno je kompleksno, delikatno konstruirano, a ipak je dovoljno čvrsto da drži pticu tisućama kilometara u visini. Poput svega u prirodi perje je evoluiralo milijunima godina do današnjeg oblika. Teško je i zamisliti kako se to dogodilo. Kako su npr. izgledali posredni oblici? Kakva je korist od polovice krila, prekrivene polu-perjem? Zahvaljujući znanosti, danas znamo da su ptice potomci dinosaura. Vidljiva je srodnost njihovih kostura. Neki dinosauri dijele određene anatomske osobine s pticama koje ne nalazimo kod drugih životinja, npr. natprsna kost. Krajem 1990-ih paleontolozi su pronašli dokaz za tu ideju: Dinosaure s ostacima perja koji su ostali očuvani na njihovom tijelu. Otada su znanstvenici pronašli desetke vrsta dinosaura s ostacima perja. Neki su bili mali poput golubova a neki veliki poput autobusa. Pogledamo li njihovu povezanost na obiteljskom stablu evolucija perja ne čini se sasvim nemogućom. Najudaljeniji pernati srodnici ptica imali su ravno perje poput žica. Potom su se te žice razdijelile u jednostavne grančice. Kod mnogih vrsta dinosaura to jednostavno perje evoluiralo je u kompleksnije perje poput onoga kakvo danas nalazimo na pticama. U isto vrijeme, perje se proširilo tijelima dinosaura, pretvarajući se od rijetkog paperja u gusto perje, koje je prekrivalo čak i noge. Neki su fosili čak sačuvali i molekule koje perju daju boju. Otkrivaju prekrasnu paletu boja: sjajno tamno perje koje podsjeća na vrane, zatim na crne i bijele pruge, ili mrlje žarko crvene. Neki dinosauri su imali visoke krijeste na glavi, ili dugačko i uzbudljivo perje na repu. Međutim, nijedan od tih dinosaura nije mogao letjeti - ruke su im bile prekratke a ostatak tijela pretežak. No ptice ne koriste perje samo za letenje. Šljuka koristi svoje perje kako bi se savršeno stopila s okolinom. Noj raširi svoja krila iznad gnijezda kako bi zaklonio mlade. Paun pokazuje svoje predivno perje na repu kako bi privukao ženke. Perje je moglo imati te funkcije i kod dinosaura. No kako su pernati dinosauri poletjeli još uvijek je misterij. No ako su dinosauri sitnog perja mahali rukama penjući se uzbrdo, njihovo perje bi im dalo dodatni potisak kako bi brže trčali. Ta slučajnost fizike mogla je dovesti do evolucije dužih ruku u dinosaura, koje bi im omogućile brže trčanje te čak i kraći let. Naposljetku, ruke su postale krila. Tek tada, možda 50 milijuna godina nakon pojave prvog perja nalik na žicu dinosauri su se vinuli u nebo.