What birds see.

• Autores: Timothy H. Goldsmith
• Localización: Scientific American, ISSN 0036-8733, Vol. 295, Nº. 1, 2006, págs. 68-75
• Idioma: inglés
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• Resumen

  • This article focuses on the vision of birds. Color vision of vertebrates depends on cone cells in the retina. Birds, as well as lizards, turtles and many fish, have four types of cone cells, whereas most mammals have only two types. The progenitors of mammals had the full complement of cones, but during a period in their evolution when they were mainly nocturnal--and thus color vision was not crucial to their survival--early mammals lost two types of cone cells. The ancestors of a group of Old World primates, which includes humans, "reclaimed" a third cone by means of mutation of one of the existing cones. Most mammals, however, still have only two cones, making mammalian color vision--even that of humans and their kin--distinctly limited when compared with the visual world of birds.