Ed Yong talks about eyes and fish evolution on The Atlantic:
Eyes are expensive organs: it takes a lot of energy to maintain them, and even more so if they’re big. If a fish is paying those costs, the eyes must provide some kind of benefit. It seems intuitive that bigger eyes let you see better or further, but MacIver’s team found otherwise. By simulating the kinds of shallow freshwater environments where their fossil species lived—day to night, clear to murky—they showed that bigger eyes make precious little difference underwater. But once those animals started peeking out above the waterline, everything changed. In the air, a bigger eye can see 10 times further than it could underwater, and scan an area that’s 5 million times bigger.
In the air, it’s also easier for a big eye to pay for itself. A predator with short-range vision has to constantly move about to search the zone immediately in front of its face. But bigger-eyes species could spot prey at a distance, and recoup the energy they would otherwise have spent on foraging. “Long-range vision gives you a free lunch,” says MacIver. “You can just look around, instead of moving to inspect somewhere else.”
Eyes are fascinating organs. My Arts Editor and I once wrote a novel which depended, in part, on the the weird eyes of trilobites. Those weird eyes, dozens of images – must have take some brainpower to integrate them.
Or did they? Maybe the integration wasn’t all that good – a sort of vague idea of the food target, open wide and hope to get it.
Sort of like a baleen whale, now that I think about it.
