The prevalence of red hair among individuals of Irish descent is a notable genetic characteristic. This trait is determined by a recessive gene, primarily the MC1R gene, variations of which result in reduced melanin production and increased production of pheomelanin, the pigment responsible for red hair and fair skin. For an individual to exhibit this phenotype, they must inherit two copies of the mutated MC1R gene, one from each parent. This genetic inheritance pattern accounts for the concentration of this trait in certain populations.
The higher frequency of the MC1R gene mutation in Ireland, and other regions of the British Isles, can be attributed to a combination of factors including genetic drift, founder effect, and potentially natural selection. In regions with less sunlight, fair skin and red hair, linked to the MC1R mutation, may have provided a selective advantage by allowing for more efficient vitamin D synthesis. The cultural isolation of certain communities within Ireland over centuries also contributed to maintaining and amplifying this genetic trait within those populations.
