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Msg. 11822 of 54959
(This msg. is a reply to 11816 by faul) |
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It seems that we adapted to become effective daylight hunters. Much of this involved the rearrangement of our pelvis which reduced power but massively increased range. It seems large eyes generally lack movement. wiki: "Birds have the largest eyes relative to their size within the animal kingdom, and movement is consequently limited within the eye's bony socket." "The performance of the eye in low light levels depends on the distance between the lens and the retina, and small birds are effectively forced to be diurnal because their eyes are not large enough to give adequate night vision. " "Nocturnal birds have eyes optimised for visual sensitivity, with large corneas relative to the eye’s length, whereas diurnal birds have longer eyes relative to the corneal diameter to give greater visual acuity." as we see, there are trade-offs in optics. Eye size alone does not dictate night vision as also the nature of the photo-receptor (the rods and cones thing) those with the greatest sensitively lack the ability to distinguish color. Human night vision is not that bad when fully acclimated, but a brief flash of a flashlight is all it takes to send us back down the 30 minute path of full acclimatization. Human eyes have excellent range of motion, very good color perception(birds having a forth pigment can dip into "a bit of the ol' ultraviolet" and it is without a doubt that birds have massive eyes (vs body weight) often flatter eyes, all sorts of additional membranes, remarkably high receptor density in the fovea, and much greater refresh rates. Humans when looking at a blinking light source typically perceive it as continuous at around 50-60Hz, birds up to and beyond 100Hz. Were we to fly, the branches and so on would be as a blur to us. Flying at spread head-first without a helmet requires same damn good eyes. Similarly birds have a much deeper focal plane, again, their rate of travel requires that more of what is in front of them is in focus at a particular moment. Homo erectus, on the other hand, can simply clock about 8-10mph for HOURS during daylight and run down pretty much any large herbivore on the planet. It may take a day or two, and Homo erectus eyes are fit for the task, excellent field of view, adequate depth perception, remarkably trainable to darkness (albeit slow and spoilable) with very high movement and field size enabling the final slay. Our adaptation migrated away from a requirement for outstanding vision (but our vision is by no means poor) towards critical features of mobility and heat-regulation. Most dogs would fail running a marathon, humans can do it on consecutive days. For this we gave up power, increased longitudinal efficiency, dramatically improved heat regulation (perhaps the most evolved heat regulation on the planet) and as such relied less on instant fast strong + high acuity vision in exchange for a jack-of-all-trades vision system coupled to a remarkably mobile well-temperature regulated predator. One simply did not want to be a large herbivorous when Homo erectus got you in the cross-hairs. Home erectus will run you down and will eat you. Our powerful knuckle dragging ancestors were left in the dust by the running deer. Homo erectus ate the running dear. You can run but you cannot hide. We sacrificed resolution at a distance (as in birds and so on) with quality eye movement, the ability to discriminate 10 million colors, and the use of these features to identify sound materials and manufacture quality tools.
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