A molecule associated with stem cell function is a key factor in human hair color.

A new study from the Stanford University School of Medicine has shown for the first time how our molecular basis can determine human hair color, as well as how subtle DNA changes can echo through our genes in such a way that it can even affect evolution.

The researchers involved in the study discovered that blond hair that is common among Northern Europeans is the result of a solitary change in the DNA that controls the expression of a gene that encodes stem cell factor.

David Kingsley, PhD, professor of developmental biology and senior author of the study, says that subtle changes in the protein KITLG may control hair color in some situations, and even stem cell division in other situations when under the influence of a different regulatory region. Varying the DNA in subtle manners could influence many different traits.

The researchers had some clues about which regulatory regions affect hair color, including the fact that the change in adenine-to-guanine nucleotide was already associated with the blond hair trait common among Northern Europeans.

“We’ve been trying to track down the genetic and molecular basis of naturally occurring traits — such as hair and skin pigmentation — in fish and humans to get insight into the general principles by which traits evolve. Now we find that one of the most crucial signaling molecules in mammalian development also affects hair color,” said Kingsley in a statement.

The findings of the study are published online in Nature Genetics.