Comment by ETH_start
4 hours ago
It is plausible that the original non-avian theropod dinosaurs which gave rise to avian theropod dinosaurs like modern birds were more vision-oriented predators than mammalian predators.
That would have favored eyes built for sharper vision at the expense of higher metabolic demands.
The different evolutionary track may come from the fact that theropods stood upright on two legs, so they could scan farther across the landscape. Also, they were active during the day. Early mammals, by contrast, were mostly nocturnal, so hearing and smell mattered more than sharp vision.
Interestingly, humans have some of the best vision in the animal kingdom and humans are both upright standing and diurnal, i.e. active in the daytime.
Which means the Jurassic Park tyrannosaur that could only see things that moved was probably seriously inaccurate (also in reality it probably had feathers).¹
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1. While checking Wikipedia to confirm my belief about feathers, I found that the consensus among paleontologists was that tyrannosaurs had superb vision, better than humans, in fact.
It is theorized that they had vision like eagles or possibly exceeded that of eagles that enabled them to see prey at great distances. Then using their legs optimized for locomotion, they would chase them down.
It feels like most people mix the two things up: excellent vision and predatory response. An eagle can absolutely see a mouse hiding in the bushes, not moving. But a moving prey is what triggers their predatory response. Plausibly… they probably don’t attack a non-moving mouse because it could be a dead mouse.
Human vision evolved for different things. Our ancestors were tree-dwelling and optimized for depth perception, social cues and color acuity. So it’s just a different strategy.
It really hit me moving to Australia, most of the mammals are nocturnal (Kangaroos were the ones that caught me most by surprise) - most (if not all) of the reptiles are diurnal - got to have that sweet sweet sun to warm the blood.