[__ Science __ ] Has the Primate Visual System Been Preserved Through Millions of Years?

[AIG.com]

Scientists compared the visual system of a lemur with other primates and found that “the size of these visual processing units is identical in all primates.”

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[Barbarian]

In all likelihood, a lot of it is preserved, since primates are remarkably alike in being mostly visual and in having binocular vision, a huge advantage for arboreal animals. And this adaptation has been so useful that once it evolved, it was retained in all primate species. The first identifiable primates, the plesadapiforms didn't have relatively large brains. They still had side-vision like most other mammals. The adapiform primates had front-facing eyes, and larger brains quickly appeared in their line. Which supports the idea that large optic processing centers evolved about the same time as binocular vision, for reasons scientists already had figured out.

Advanced primate eyesight is a remarkably good adaptation, one that has been preserved by natural selection for many millions of years. But it began with forward-facing eyes, not the very first primates.

 

[Truthfrees]

Scientists compared the visual system of a lemur with other primates and found that “the size of these visual processing units is identical in all primates.”

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thanks for sharing truth

 

[Barbarian]

The Royal Society​

Visual specialization and brain evolution in primates​

R. A. Barton
Published:22 October 1998
Here I show that, among primates, brain size variation is associated with visual specialization. Primates with large brains for their body size have relatively expanded visual brain areas, including the primary visual cortex and lateral geniculate nucleus. Within the visual system, it is, in particular, one functionally specialized pathway upon which selection has acted: evolutionary changes in the number of neurons in parvocellular, but not magnocellular, layers of the lateral geniculate nucleus are correlated with changes in both brain size and ecological variables (diet and social group size).

No surprise to find that larger brains and optic tecta are a constant in more evolved primates. It's no more surprising than to find that giraffiform ungulates tend to have longer necks. (for different reasons).

 

[Truthfrees]

Scientists compared the visual system of a lemur with other primates and found that “the size of these visual processing units is identical in all primates.”

Continue reading...

cool - thanks

"The reason primate vision hasn’t evolved in fifty-five million years—and why vision is so complex from the beginning—is because it didn’t evolve! God created it from the very beginning, fully formed and functioning, so primate kinds and humans could see the world they live in."

 

[Barbarian]

As you see, the development of the large brain of primates dates from the time that they evolved binocular vision with both eyes facing forward, rather than to the side as seen in very early primates. That encouraged binocular vision and less reliance on smell for information. However, there have been lots of evolutionary changes in primate vision.

One of those was color vision. Almost as soon as binocular vision evolved, so did the ability to see colors. Tarsiers have tricolor vison as we do. This is surprising, considering that color vision is of little use a night, suggesting that Tarsier ancestors were diurnal. Some exclusively nocturnal primates have lost color vision.

Very early primitive fossil primates like Notharctus had enlarged olfactory bulbs in the brain, but lacked an enlarged visual cortex. It was diurnal, suggesting that the shift to vision as the primary sense had not yet evolved in primates at that time.

So far, we don't have a complete skull of Purgatorius, the earliest known primate. It is likely that it also has a relatively primitive visual system, but that will have to be resolved when a more complete skull is found.