Eye evolution as a driving force in the move of fish from water to land
Lars Schmitz
400 million years ago, fish made the evolutionary leap from water to land. If they hadn’t, you might not be reading this sentence. Why? Because it led to more complex cognition. A new study by Northwestern professor Malcolm MacIver and Claremont Colleges professor Lars Schmitz discovered a near tripling of eye size might be what triggered the invasion of land. They show that this increase in the eye size of animals that span the gap between fish and four-legged land animals was most likely because these animals were poking their eyes---which had moved from their fish-like position on the side of the head to a crocodile-like position perched on the top of the head---just above the water line. With their eyes out of water, these animals could see much further out to a host of millipedes, centipedes, spiders, and other invertebrates that started living on land long before. Larger eyes were consequently selected for, whereas in water the study shows that larger eyes led to negligible increases in range. Larger eyes looking far out to a “buena vista” of unexploited prey through air may have been key in driving these crocodile-like fish to evolve into the first vertebrates on land.
The massive increase in visual capability enabled by vision out of water allowed early limbed animals to evolve more complex cognition, since they were no longer forced to react with split-second speed as required by life in the water. Eventually we have the human capability of prospective cognition---the power to weigh options for the future and choose strategically. But while we can strategically weigh options that are near in time or space, is our inability to act decisively on more distant looming problems perhaps rooted in this evolutionary history?
Read more about the study “Massive Increase in Visual Range Preceded the Origin of Terrestrial Vertebrates" in Northwestern Now:  


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