When searching, there are some hypotheses that can be quickly refuted, such as the hypothesis of the camouflage of predators or the premise that these colors prevent the attraction of some insects such as mosquitoes and thus not to transfer some fatal diseases.
In fact, if the hypothesis of camouflage is correct, we should have found this feature in other creatures living in the same conditions as zebra. For example, we have to find deer or other animal species that have some kind of a line for camouflage. The hypothesis of camouflage assumes that the Lions (the first predator of the zebra) find it difficult to catch zebra but this is simply not true because Lions hunt wild donkeys continuously without any mention of disguise. Yes, the Lions see only two colors. These lines may contribute to the concealment of the zebra among the weeds, but if there is any benefit to these lines, they are an output and not the primary motivation for development.
The hypothesis of the flying insect's plane says that the black color of the scalp, in general, attracts a kind of flying insect as the polar light is reflected by the Black Horse's back. Similar to the light polarity of the water pools and swamps where these insects place their eggs, so the presence of the white color near the color Black changes the optical polarity reflected by the zebra's back, which alienated the insects from landing on the back. This hypothesis also does not explain the non-appearance of these lines on horseback in other geographical locations other than the African environment. For example, we do not find planned horses in the regions of Asia, Europe and the Americas. Yes, some might say that these horses are hybrid, but yet we find no evidence that these lines appear on any horse types except on the African continent and what we call the Donkey monster specifically.
Cooling hypothesis:
The hypothesis that I find fits into the theory of evolution is the cooling hypothesis as the lines on the back of the zebra are acting as an external cooling system for the body through a mechanism that I will explain in the next lines.
How does the cooling process happen?
The onset of the color relationship must be explained with the ability to absorb the rays of the sun as this African organism lives in an environment exposed to sunlight throughout the day. Without getting into the physical details of what colors, the colors are a reflection of the light waves on the materials around us. For example, when we look at a blue car, we look at a body coated with a substance that absorbs all the optical waves, with almost 475 nm or what we're translating into our brain in blue form. Looking at the foliage, we look at organic materials that have electrons that absorb all photons and reflect only the 510-NM or what we call green. When we look at a yellow-colored substance, it is an electron that absorbs all the microwave waves with about 570 nanometers, which we translate into a yellow color and when we look at a transparent material, we look at a substance that has stimulating electrons to the point that they need higher frequencies than the visible waves. For us to absorb it, the electrons seem to us to be transparent. When you look at a multi-color material it is a variety of atoms each with different characteristics that reflect the frequencies that we can monitor.
Organisms living in an environment exposed to sunlight for long periods of time form an evolutionary pressure (that is, whoever does not have this feature died) to produce a dye that protects them from the damage of sunlight. The sunlight negatively affects the accuracy of the DNA of the organisms and thus the organisms that did not have the abilities to protect themselves from ultraviolet rays have been extinct leaving the field for organisms that have melanin pigment. The melanin dye is done in the body when the body is exposed to ultraviolet radiation, which changes the skin color of the hair more. This chromosome is found in humans and most of the sun-exposed neighborhoods are large.
The basic color of the zebra is black, but evolutive pressure has given precedence to all the individuals who have shown white refinement on their bodies. What is this evolutionary benefit?
When you preview the horse in general and the zebra, in particular, we find that their digestion is not as effective as their other counterparts of herbal eaters so the zebra has to spend more time in the weeds. The horse has a relatively small stomach for the size of his body and possesses a digestive tract closer to humans than other livestock and therefore needs a long time to complete the process of eating and digestion which exposes it to the sunlight for long periods.
Although melanin dye protects DNA from the damage caused by sunlight, the black color produced by melanin absorbs all the frequencies of the optical spectrum and turns it into thermal energy. I mentioned earlier that the colors are absorbing all the optical frequencies and reversing a certain frequency which shows the human eye as "color" but the color is not a basic thing but a brain translation of this photolysis only. Black is only the embodiment of the absorption phenomenon of all optical frequencies and not the opposite of any of them. It should be noted here that the color of melanin dye is a chemical result and not a color related to the solar radiation protection process. Black is absorbing the heat of the sun and thus raising temperatures and in return for the neighborhoods to find a way to get rid of this excess heat.
In the case of man, the human body develops so that it secretes the body to cool and in the case of a zebra, the body develops so that parts of the body will appear without melanin dye. The physical benefit of not having melanin is a constant thermal transition from top to bottom (entropy), so the absorbed heat moves towards the colder refinement of the body. This thermal transmission is similar to the one that produces wind on earth, where sunlight heats the air and climbs upward, but begins to move to the less-heated areas than it seems to us as a wind.
The cold-blooded cooling system is similar to a very small wind resulting from the temperature imbalance between the patches of the skin, which contributes to the overall cooling of the body. This hypothesis if it is true, we must find a correlation between the geographical location (temperature) and the extent of the white color spread on the body of the zebra.
As I mentioned earlier, this hypothesis has not been empirically verified but I think it is the most correct so far.
Imagine that human sweating is matched by the beautiful white lines on the body of the zebra and that these white lines on the zebra depend on the same physical mechanism as the wind.