Do you know why snakes didn t form a normal visual system during evolution?

After the mass extinction event (which occurred at the turn of the Permian and Triassic), our ancestors fell from the status of land hegemon, and most of them became extinct during the mass extinction event, while the surviving ones were suppressed by the later dinosaur ecology throughout the Mesozoic Era and forced to become nocturnal small animals. And this dark history has left a deep imprint on the only surviving descendants of the class Zygokosa - mammals. Almost all mammals have dichromatic vision – they lose the cone of two color visions in the dark, freeing up more space for rods that are sensitive but have no ability to discriminate color, because color vision is less useful in the dark, and the ability to perceive weak light is particularly important.

The vast majority of mammals are red-green color blind, only the primates re-evolved a third color vision in later evolution - in order to distinguish whether the fruit is ripe, and this third color vision is not a recovery of a color vision in the previous four-color vision, but through the small modification of red vision to gain the ability to feel green, but this gene mutation is not stable, so there is still a high proportion of red and green color blindness in humans. The development of mammalian color vision also proves that it is not easy to regain lost traits.

But nocturnal walking also gives mammals some extra abilities. As mentioned earlier, mammals sacrifice color vision for night vision. Even mammals with relatively poor night vision, such as humans, can see far better at night than almost all birds (if you don't believe me, try catching a chicken or any other bird on a dark night, but not owls).

The snake has a slender and legless body, suggesting that the early evolution of the snake may have been underground. Fossil studies also provide relevant evidence: "From the study of snake fossils, scholars believe that snakes evolved from a line of cave-dwelling lizards from the Cretaceous era, such as monitor lizards or other neighboring species.

An early fossilized snake named "Najashrionegrina" is believed to be a bipedal burrowing creature that already has a sacral skeleton and a completely terrestrial habit. "Because these ancient creatures lived in burrows, their limbs gradually degenerated and disappeared, and their bodies became more streamlined, making it easier to enter and exit the burrows. According to this hypothesis, some of the characteristics of snakes, such as their transparent eye membranes (which function like eyelids) and the lack of external ears, can be explained by the fact that they evolved to facilitate their movement in the crypts.

There are also some ancient snakes that had hind limbs, but there was no direct connection between the pelvic bones and the spine of their bodies, such as Pachyphyllum and Euphyllum snakes, which are believed to have survived much older than the "najash" fossils. ”

Since living in a dark hole, vision obviously does not play a big role, so it is degraded. Modern snakes have returned to the ground, but their vision has deteriorated, but they have developed senses such as snake letters, so they can also adapt to life on the ground, and it takes luck to regain their vision. There are a few arboreal snakes with relatively better eyesight, but they are still much worse than most other terrestrial vertebrates.

In fact, a similar evolutionary process occurred in mammals. The vast majority of sauriformes—birds, dinosaurs, crocodiles, lizards, and their ancestors, amphibians—are masters of color discrimination with tetrachromatic vision, and our mammalian ancestors, as descendants of amphibians, are believed to also have tetrachromatic vision.

Because the snake's eyesight is very poor, it is better to increase other aspects than Daisuke's eyesight.

The mammal's unprecedentedly powerful sense of smell is also due to the nocturnal walk - the nose, which is the "snake letter" of mammals.

This may be the result of natural evolution.

But after the mass extinction event (which occurred at the turn of the Permian and Triassic), our ancestors fell from the status of land hegemon, and most of them became extinct during the mass extinction event, and the surviving ones were suppressed by the later dinosaur ecology throughout the Mesozoic Era and forced to become nocturnal critters.

Because vision is its weakness, there is no need to strengthen it.

Adapt to life on the ground, and regain your vision.

It's all about adapting to the living environment.

The main thing is that the direction of evolution is different.

Because this is the most suitable way for snakes to survive.

Such a morphology suggests that the early evolution of snakes may have been underground.