Why do some humans have blue eyes and others have brown eyes?

Answer 1

I believe it was an envolutionary response to the environment just like skin pigment and nose shape.

Darker skin seems to work well and doesn't require perperation for cooling in normal tropic environment.

Long nose will warm cold air to manageable temperature. Flat nose just get's air in, possibly in larger volume to compensate for higher humidity.

Blue eyes seem to be a result of northern latitudes where there was perodic reflection from the snow and different angle of the sun's rays.

Well that's my thought but if you want to know the real answer go to: http://en.wikipedia.org/wiki/Iris_%28anatomy%29#Genetic_and_physical_factors_determining_iris_color

Answer 2

This is genetic. If your parents both have blue eyes, you have a 75% chance of having them, too. This is a dominant gene. The remaining 25% is due to recessive genes. If either of your parents have another color as a recessive, such as your grandmother on your father's side had brown eyes, but the grandfather had blue, and both of your mother's parents had blue, the brown is recessive and can show up in later generations.

Answer 3

Differences in iris color depends on the amount of pigmentation in the deep stroma, especially the anterior border layer, and on the density of the stroma, both of which influence how much light, and what wavelengths, are absorbed and reflected. As with other objects, the color we see is the result of reflected light. The stroma of brown irises is densely pigmented with melanin and absorbs much of the light that enters it. In many human populations, brown is the only eye color. Blue irises have lightly pigmented stroma, and light of longer wavelengths (red to yellow) readily penetrates the iris and is absorbed, while some light of shorter wavelength (blue) is reflected back and scattered by the iris stroma; hence the blue color.

The inability to make melanin, as in albinism, leaves the iris without any pigment. The iris appears pink from the color of the blood flowing through it. Albinism is a recessive condition, requiring two defective alleles for melanin production, one inherited from each parent. Albinism also prevents pigment production in the hair and skin.

Answer 4

this question deals with genetic dominance. Traits in your DNA are biased into taking the trait that is stronger. If your mother has blue eyes and your father has brown eyes. If you have blue eyes, then the gene for blue eyes dominated over that trait from your father.

For more information, look up mendal's pea plant experiments and punnett squares

Answer 5

Eye color is determined by the genes that we inherit from our parents. The basic pattern is that a brown gene is dominant over a blue gene, but obviously there are other variations, like hazel, grey, and green eyes (as well as the rare violet-eyed individual).

Answer 6

genetics. Blue eyes are less common because they are a recessive gene, and brown eyes are a dominent gene.

Answer 7

Well, it depends on your horomones. The human body has Purebred genes and Rescessive genes. Each person has a gene for their eye color. It's a little too complicated to explain for me, so visit http://en.wikipedia.org/wiki/Punnett_square if you have more questions ask me; I'm studying this in school.

Answer 8

The jeans in the DNA make your eyes the colors that they are

Answer 9

It's down to genetics. It's actually the amount pigmentation in the stroma.

Answer 10

Through gene expression.