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Vision, not limbs, took us onto land 385 million years ago

Thursday, March 9, 2017 12:26
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A new study discovered it was vision and not locomotion that first caused our aquatic forebears to make the significant transition from life in the water to life on land.

Published in the journal Proceedings of the National Academy of Sciences, the study said crocodile-like animals were drawn to land by the food they saw there and then evolved limbs that allowed them to get there.

The study team reached their conclusion via a thorough examination of the fossil record. They found that the eyes of our ancestors become three times bigger before the transition to land. The rapid expansion happened simultaneously with a change in positioning of the eyes; from the sides of the head to the top. The enhanced visual range of looking through air may have gradually led to bigger brains in early terrestrial vertebrates and the capacity scheme and not just react on instinct, which is what fish do.

Discovering Why We Came Onto Land

“Why did we come up onto land 385 million years ago? We are the first to think that vision might have something to do with it,” study author Malcolm A. MacIver, an engineer and neuroscientist at Northwestern University, said in a news release.

“We found a huge increase in visual capability in vertebrates just before the transition from water to land,” he continued. “Our hypothesis is that maybe it was seeing an unexploited cornucopia of food on land — millipedes, centipedes, spiders, and more — that drove evolution to come up with limbs from fins.”

The development of larger eyes would have been a game-changer. By simply being able to see above the water line, these animals could look 70 times farther than they could in water. This, in turn, would have exponentially expanded the animal’s viewable space.

“Bigger eyes are almost worthless in water because vision is largely limited to what’s directly in front of the animal,” said co-author Lars Schmitz, assistant professor of biology at the W.M. Keck Science Department. “But larger eye size is very valuable when viewing through air. In evolution, it often comes down to a trade-off. Is it worth the metabolic toll to enlarge your eyes? What’s the point? Here we think the point was to be able to search out prey on land.”


Image credit: Malcolm MacIver, Northwestern University

The post Vision, not limbs, took us onto land 385 million years ago appeared first on Redorbit.
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