Most babies are born blue-eyed. But this circumstance does not mean anything at all, because the color of the eyes will not change again. How to explain such a strange phenomenon?
The color of the eyes depends on the amount of melanin - the pigment, which accumulates in the iris. Than this substance is less, so they are lighter. Most babies have eyes that are either blue, or blue, or gray, because the birth of melanin in the iris is still small. Special cells (melanocytes), which produce it, are included in the work gradually. About the final shade of the eye can be judged only to 10-12 years, when the pigment accumulates exactly as much as measured by genes, because this parameter is passed on to the child by inheritance.
But there is another reason, explaining the advantage of blue and gray tones. Iris consists of anterior and posterior sheets. In the background, melanin accumulates even before birth, and in the fore - only a few weeks after the appearance of crumbs into the light. Since the front sheet of newborns is not colored, the shade of the eyes is attached to the gray-white walls of the blood vessels, through which the iris is permeated. If they are close to each other, the sunlight almost does not dissipate and the eyes appear gray. If the blood vessels are quite far apart, the light dissipates well, and the eyes become bright blue. Normally, the pigment accumulates on the front sheet to 2-3 years, and at the same age, the first color changes begin. Bright eyes can darken, but the reverse process is almost impossible. Many children, especially the blonde from birth, the eye color changes not one, but several times.
Approximately 1% of babies are born with heterochromia, that is, with eyes of different hues. This means that in one eye of the pigment accumulated a little more than in the other. It is not worth worrying: in sight this feature will not be reflected in any way. But partial heterochromia is more common, when parts of the iris of one eye are colored in different colors.Black eyes
The color of the eyes depends on many genes. In 30% of cases, light-eyed children can have dark-eyed parents. The scientists were able to explain this fact not so long ago.
Scientific minds came to the conclusion that people with blue eyes have one common ancestor. They found a gene that mutated about 6-10 thousand years ago, which led to the appearance of caste light-eyed caste. Until then, all the earthlings were dark-eyed. According to one of the hypotheses, the first owner of the blue eyes was from the Middle East or the Black Sea coast. But brown-eyed still dominate: they make up a large half of the world's population. Green eye color is caused by a low or moderate level of melanin and the presence of a yellow pigment of lipofuscin. Its owners are most often women, but why this is so, science is still unknown.Read on this topic:
- A sharp eye
- Genetic Engineering
- Heredity and child planning