On the origin of feathers.

Feathers are one of the most characteristic evolutionary novelties of birds, and until recently a broad consensus existed that typical vaned feathers (pennaceous feathers) evolved in an aerodynamic context to streamline the body and form lift-generating surfaces. Based on the occurrence of essentially modern-type pennaceous feathers in a number of flightless non-avian theropod (“beast-footed”) dinosaurs, Foth et al. recently proposed that these feathers originated in a context other than flight ([ 1 ][1]). In their Perspective “Beyond the rainbow” (24 October, p. [416][2]), M.-C. Koschowitz et al. argue that vaned feathers evolved for signaling with structural coloration. This hypothesis is, however, highly implausible from an evolutionary point of view. ![Figure][3] Caudipteryx dinosaurs were flightless yet had pennaceous feathers. ILLUSTRATION: FRIEDRICH SAURER/SCIENCE PHOTO LIBRARY In most flightless birds, the feather vanes lose their integrity, which indicates that pennaceous feathers evolved to serve aerodynamic functions. In extant birds, signal feathers are usually restricted to small portions of the plumage, which further challenges the hypothesis that pennaceous feathers mainly evolved for display reasons. Moreover, display feathers often do not have a pennaceous structure, but form loose feather bunches or elaborate ornamental structures. Display feathers are almost always restricted to one sex, usually the males. If pennaceous feathers mainly evolved to serve display purposes, why do female birds have exactly the same basic feather morphologies as the males? Even if some theropods with pennaceous feathers can be shown to have been primarily flightless, the “wing-assisted incline running” hypothesis provides an aerodynamic context for the evolution of feathers in nonflying animals with limbs adapted for running ([ 2 ][4]). Hypotheses for their evolution in a nonaerodynamic context are therefore not only evolutionarily implausible but also not necessary to explain their origin. 1. [↵][5]1. C. Foth, 2. H. Tischlinger, 3. O. W. M. Rauhut , Nature 511, 79 (2014). [OpenUrl][6][CrossRef][7][PubMed][8][Web of Science][9] 2. [↵][10]1. K. P. Dial , Science 299, 402 (2003). [OpenUrl][11][Abstract/FREE Full Text][12] [1]: #ref-1 [2]: /lookup/doi/10.1126/science.1258957 [3]: pending:yes [4]: #ref-2 [5]: #xref-ref-1-1 "View reference 1 in text" [6]: {openurl}?query=rft.jtitle%253DNature%26rft.stitle%253DNature%26rft.aulast%253DFoth%26rft.auinit1%253DC.%26rft.volume%253D511%26rft.issue%253D7507%26rft.spage%253D79%26rft.epage%253D82%26rft.atitle%253DNew%2Bspecimen%2Bof%2BArchaeopteryx%2Bprovides%2Binsights%2Binto%2Bthe%2Bevolution%2Bof%2Bpennaceous%2Bfeathers%26rft_id%253Dinfo%253Adoi%252F10.1038%252Fnature13467%26rft_id%253Dinfo%253Apmid%252F24990749%26rft.genre%253Darticle%26rft_val_fmt%253Dinfo%253Aofi%252Ffmt%253Akev%253Amtx%253Ajournal%26ctx_ver%253DZ39.88-2004%26url_ver%253DZ39.88-2004%26url_ctx_fmt%253Dinfo%253Aofi%252Ffmt%253Akev%253Amtx%253Actx [7]: /lookup/external-ref?access_num=10.1038/nature13467&link_type=DOI [8]: /lookup/external-ref?access_num=24990749&link_type=MED&atom=%2Fsci%2F346%2F6216%2F1466.2.atom [9]: /lookup/external-ref?access_num=000338199400039&link_type=ISI [10]: #xref-ref-2-1 "View reference 2 in text" [11]: {openurl}?query=rft.jtitle%253DScience%26rft.stitle%253DScience%26rft.aulast%253DDial%26rft.auinit1%253DK.%2BP.%26rft.volume%253D299%26rft.issue%253D5605%26rft.spage%253D402%26rft.epage%253D404%26rft.atitle%253DWing-Assisted%2BIncline%2BRunning%2Band%2Bthe%2BEvolution%2Bof%2BFlight%26rft_id%253Dinfo%253Adoi%252F10.1126%252Fscience.1078237%26rft_id%253Dinfo%253Apmid%252F12532020%26rft.genre%253Darticle%26rft_val_fmt%253Dinfo%253Aofi%252Ffmt%253Akev%253Amtx%253Ajournal%26ctx_ver%253DZ39.88-2004%26url_ver%253DZ39.88-2004%26url_ctx_fmt%253Dinfo%253Aofi%252Ffmt%253Akev%253Amtx%253Actx [12]: /lookup/ijlink/YTozOntzOjQ6InBhdGgiO3M6MTQ6Ii9sb29rdXAvaWpsaW5rIjtzOjU6InF1ZXJ5IjthOjQ6e3M6ODoibGlua1R5cGUiO3M6NDoiQUJTVCI7czoxMToiam91cm5hbENvZGUiO3M6Mzoic2NpIjtzOjU6InJlc2lkIjtzOjEyOiIyOTkvNTYwNS80MDIiO3M6NDoiYXRvbSI7czoyNToiL3NjaS8zNDYvNjIxNi8xNDY2LjIuYXRvbSI7fXM6ODoiZnJhZ21lbnQiO3M6MDoiIjt9