Here's why:
* Melanin: Freckles are caused by clusters of melanin, the pigment that gives skin its color. Redheads and blondes have less overall melanin, but they have a higher concentration of a specific type of melanin called pheomelanin, which is responsible for red and yellow tones. This type of melanin tends to clump together, creating freckles.
* Genetics: The tendency to develop freckles is largely determined by genetics. People with lighter hair and skin are more likely to inherit the genes that make them prone to freckles.
While brunettes can also have freckles, they are less common because they have higher levels of eumelanin, the melanin responsible for brown and black pigment. Eumelanin doesn't clump as easily as pheomelanin.
It's important to note:
* Sun exposure: Sun exposure can trigger the development of freckles in anyone, regardless of their hair color.
* Individual variation: There is always individual variation, and some people with dark hair may have more freckles than some people with light hair.