The eyes have it

Improved vision rather than powerful limbs allowed early vertebrates to make the transition from water to land

20 Mar 2017 by Selina Powell

In a paradigm shift for evolutionary theory, a new study suggests bigger eyes and an expanded visual range preceded and propelled the transition of vertebrates from water to land.

The research, published in Proceedings of the National Academy of Sciences, involved scientists assembling 1000 evolutionary trees for 59 fossil animals. All of the fossils had measurable eye sockets and skulls.

Analysis revealed that the average eye socket size of animals following the shift to terrestrial living was three times larger than that of animals who existed before the change of habitat.

The research also illustrated that the placement of the eyes changed from the side of their heads to the bony ridges on top, allowing them to see above the water like crocodiles. This change occurred long before fins evolved into limbs.

Computer simulations of the animals’ environments suggest that larger eyes improved the ability of animals to spot prey on the shore. According to the study authors, enhanced long-distance vision may have prompted the evolution of limbs as well as the neural circuits required for terrestrial living.

Biologist and palaeontologist, Lars Schmitz, told OT that our fish ancestors developed the ability to focus on both close and far away objects.

“Optometrists may find it interesting to investigate how our lifestyles, with many hours spent in front of computers and smartphones, affects our ability to focus on both near and far objects,” he said.

“Staring at screens all day mean we are not using our eyes for the full range they are built to survey,” Dr Schmitz concluded. 

Image credit: Oxford University Museum of Natural History


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