Fish Changed in a Surprising Way Before Invading Land
Around 385 million years ago, fish started hauling themselves onto land. Over time, their flattened fins gradually transformed into sturdy legs, ending in feet and digits. Rather than paddling through water, they started striding over solid ground. Eventually, these pioneers gave rise to the tetrapods—the lineage of four-legged animals that includes reptiles, amphibians, and mammals like us. This transition from water to land is an evocative one, and for obvious reasons, people tend to focus on the legs. They are the organs that changed most obviously, that gave the tetrapods their name, and that carried them into their evolutionary future.
But Malcolm MacIver from Northwestern University was more interested in eyes.
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