As a domain expert in genetics and population demographics, I can provide you with an informed estimate based on available data and research. It's important to note that the distribution of hair and eye color can vary significantly by region and ethnicity.

Red hair is the rarest hair color, with the highest concentration found in people of Northern European descent, particularly those from Scotland, Ireland, and Wales. The percentage of the global population with red hair is estimated to be around 1-2%.

Brown eyes are much more common. They are the most frequent eye color worldwide, with estimates suggesting that approximately 55-79% of the world's population has brown eyes.

To find the percentage of the population with both red hair and brown eyes, you would typically multiply the individual probabilities, assuming they are independent traits. However, hair and eye color are not independent; they are both determined by genetics and can be linked. For instance, people with red hair often have blue or green eyes due to the genetic mutations that cause red hair (specifically, a variant of the MC1R gene).

Given these genetic correlations, it's difficult to provide an exact percentage of people with red hair and brown eyes without specific regional or ethnic data. However, we can say that it is a relatively rare combination, likely less than 1% of the global population.

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The combination of having both red hair and blue eyes is so rare because blue eye color is also a recessive trait, meaning both parents must carry the gene for a child to have it. Red hair occurs naturally in one to two percent of the human population, while just 17 percent of the world's population has blue eyes.read more >>