There is no way you can miss the cute whorls and sworls of a newborn baby’s hair. Especially if you are his mother and you kiss that sweet baby head a million times a day. But why does hair grow in these patterns? Why does the hair not grow from the nape of the neck to the top of the forehead without interruption or the other way around? Why do we have cowlicks and whorls, widow’s peaks and crown sworls?
A whorl (otherwise known as a parietal whorl, sworl or crown whorl) is a clockwise or counter clockwise rotation of hair patterning that is typically found on the back, top of the head.(1) Most people have one whorl, fewer have two and very rarely does a person have three whorls. In neonatal care, a red flag for possible aberrant brain development is the presence of more than two whorls or uncommon placement of two or more whorls.(5) Hair whorl presence and direction is strongly influenced by racial heritage, with caucasian Americans having the highest occurrence of single whorl clockwise hair patterning (95%, with 80% of those having a clockwise whorl).(4)
Whorls are most typically clockwise, but can be counterclockwise in direction. Most people have two whorls on their head, usually a dominant one at the crown of the head and another less dominant one in a different area of the scalp. The circular patterning of the hair is also known as crowns, swirls, trichoglyphs, or cowlicks.
Studies on these differences in direction have explored the possibility that hand dominance (right or left handedness) correlates with whorl direction. Most studies are inconclusive, with a potential bias towards there being more people with counterclockwise whorl patterning who are also left handed.
One particular study, by the Genetics Society of America³, found that only 8.4% of right handed people had a counter clockwise whorl, while 45% of left handed people had a counterclockwise whorl. Hand dominance and whorl direction are likely not mutually exclusive in gene expression, but do seem to pair strongly. A 1933 Identical twin study(4) of 13 pairs of twins with opposite direction whorls suggest that whorl direction is not determined by DNA alone (although epigenetics might play a part). Another study, published by the University of Munich, concluded that left-handedness was strongly correlated with a counterclockwise whorl, as well as the position of the whorl on a person’s scalp.(6)
Likewise, a 1985 Study at the Albert Einstein College of Medicine in New York found there to be a strong correlation between the position of the whorl on the scalp and hand dominance.(8) Of those right handed people, 70% had a whorl that was positioned to the left of the midliue, whereas left handed people had a 60% occurrence of the hair whorl positioned to the right of the midliue. This study was done based on the connection between brain abnormalities and hair pattern abnormalities seen in babies to help diagnose disorders of the brain that occur in utero between the gestational age of 10 to 16 weeks.(8,2) It is thought that hand dominance is determined at this same critical stage of fetal development. In right handed people, the size of the left brain hemisphere is slightly larger than the right side, which leads to right hand dominance. For left handed people, the brain hemispheres are the same size, so preference towards right handedness is not a given, which can lead to left hand dominance or ambidexterity. The Albert Einstein College study offers some compelling evidence to say that brain hemisphere size, determined in utero, may influence the location of the parietal whorl.
The takeaway is this: We are not sure why the hair patterns in whorls and such, but since aberrant brain development in utero can change the normal hair patterning or positioning, there is likely a genetic link or affect to how the hair patterns, based on brain development. The direction of the whorl does not seem to correlate as strongly to right or left handedness as does the position of the center of the whorl on the scalp.
1. What are hair growth patterns? http://www.wisegeek.com/what-are-hair-growth-patterns.htm
2. Scalp Hair Characteristics the A Newborn, Susan A. Furdon, RNC, MS, NNP, David A. Clark, MD. http://www.medscape.com/viewarticle/466530_5
3. Human Handedness and Scalp Hair-Whorl Direction Develop From a Common Genetic Mechanism, Amar J. S. Klar. http://www.genetics.org/content/165/1/269.full.pdf
4. Hair Whorl: The Myth http://udel.edu/~mcdonald/mythhairwhorl.html
5. Physical Diagnosis in Neonatology, Mary Ann Fletcher. http://books.google.com/books?id=2chdTE4SHE8C&pg=PA202&lpg=PA202&dq=parietal+hair+whorl&source=bl&ots=E6rD8H4eFd&sig=H4erlbkHkLXzGyvFLIR2gjZQd-o&hl=en&sa=X&ei=jlzPUc73OYKtiQK6-4CoAw&ved=0CDwQ6AEwAg#v=onepage&q=parietal%20hair%20whorl&f=false
6. Medial position and counterclockwise rotation of the parietal scalp hair-whorl as a possible indicator for non-right-handedness, Schmidt H, Depner M, Kabesch M.. http://www.ncbi.nlm.nih.gov/pubmed/18758663
7. The association between scalp hair-whorl direction, handedness and hemispheric language dominance, Andreas Jansen. http://www.sciencedirect.com/science/article/pii/S1053811906012158
8. 1303 CORRELATION BETWEEN PARIETAL HAIR WHORL LOCATION AND BRAIN DOMINANCE, Robert W Marlon and H M Nitowsky. http://www.nature.com/pr/journal/v19/n4/abs/pr19851405a.html