An eye is not an eye is not an eye

Image courtesy of Wikimedia Commons

National Geographic “Inside the Eye: Nature’s Most Exquisite Creation”

This is another fantastic article by Ed Yong that very nicely captures the relativistic nature of the evolutionary process. We basically call any light-sensing organ an “eye”, but animals have eyes that perform radically different functions. How eyes work is a function of both the light environment an animal inhabits and the ecological role that animal can use light information to fill. For this reason aquatic animals tend to have different kinds of eyes than terrestrial animals, and predators different eyes than prey.

But there’s also remarkable convergence in the evolution eyes, an indication that there are invariant qualities to light that make particular designs optimal for harnessing light as a source of information. How convergently eyes have evolved depends on which of their components you survey. The crystallins that make up the lenses of various eyes are similar in form but diverse in origin. And yet the crucial light-sensing opsin proteins that make all eyes possible are all derived from the same derived ancestral protein.

This article serves up a concise summary of what we know about eyes. It briefly discusses fossils, including the lack of a clear fossil sequence that would illuminate the evolutionary trajectory that yielded extant eyes. The article does illuminate the importance of extant eye diversity to our understanding of the four stages of eye evolution, and creates a nice image of how the most sophisticated eyes could have radically altered ecology by allowing for interactions at greater distances.

As you might expect from National Geographic, this article also delivers phenomenal pictures of phenomenal animal eyes of phenomenal diversity. Particularly interesting are images simulating what different animals might see with their varying eye anatomies.