What is the Origin and Reason for Red Hair.

What is the Origin and Reason for Red Hair.
Jun 9th, 2024.
Chapters:
0:00 Red Hair
1:12 Genetics of Red Hair
2:38 Genetic Inheritance of Red Hair
3:52 Origins of Red Hair
5:09 Reasons for Red Hair
6:34 My Thoughts
What is the origin of red hair and why did it develop in the first place? Now red hair is the rarest hair color in the world, at around 2% of the global population, and it is most common in people of Northern European ancestry, at around 2–6%. It is particularly associated with Celtic countries, with Scotland and Ireland having the highest percentage of people with naturally red hair in the world. Estimates seem to vary for Scotland at between 6-13% of the population, with around 10% of people in Ireland having red hair. Red heads are found in other regions across the globe however, including the Udmurt Republic of Russia, who some say possess the “reddest hair in the world.”
Interestingly, multiple studies have shown that people with red hair perceive pain differently to others. Red heads may be more sensitive to certain types of pain and can require higher doses of some pain-killing medications, and they often need about 20 percent more anesthesia to be sedated. Some studies indicate however that the general pain tolerance of red-heads may be higher. People with red hair also respond more effectively to opioid pain medications, requiring lower doses.
This is pretty wild to think, so why does this seem to be the case? Well it’s to do with the main genetic variant that causes red hair in the first place. To be more specific, red heads have a variant of the melanocortin-1 receptor (MC1R) gene located on chromosome 16, which seems to be the primary driver of red hair, although other studies have pinpointed more genes that also may play a role in whether red hair is expressed or not, but this is still being mapped.
Sources:
Are You Carrying the Redhead Gene | Ginger Gene DNA | Live Science
The genetic causes, ethnic origins and history of red hair - Eupedia
Red hair - Wikipedia
Celts' red hair could be attributed to the cloudy weather | IrishCentral.com
Edinburgh is surprise capital of redheaded Britain and Ireland (telegraph.co.uk)
Robinson KC et al. Reduced MC4R signaling alters nociceptive thresholds associated with red hair. Sci Adv. 2021 Apr 2;7(14):eabd1310. doi: 10.1126/sciadv.abd1310. PMID: 33811065; PMCID: PMC11057701.
Reduced MC4R signaling alters nociceptive thresholds associated with red hair - PubMed (nih.gov)
Study finds link between red hair and pain threshold | National Institutes of Health (NIH)
Valverde, P., Healy, E., Jackson, I. et al. Variants of the melanocyte–stimulating hormone receptor gene are associated with red hair and fair skin in humans. Nat Genet 11, 328–330 (1995). https://doi.org/10.1038/ng1195-328
Hair Color by Country 2024 (worldpopulationreview.com)
The people with the reddest hair in the world - BBC News
Recessive Traits and Alleles (genome.gov)
Oxford Blueprint: 31.05.01: Red hair genes 10