A hair whorl is a patch of
hair growing in a circular direction around a visible center point. Hair whorls occur in most hairy animals, on the body as well as on the head. Hair whorls, also known as
crowns
A crown is a traditional form of head adornment, or hat, worn by monarchs as a symbol of their power and dignity. A crown is often, by extension, a symbol of the monarch's government or items endorsed by it. The word itself is used, partic ...
, swirls, or trichoglyphs, can be either
clockwise or counterclockwise in direction of growth.
In human theories
Hair whorls on the head (
parietal whorls) have been studied by some behaviorists. Most people have clockwise scalp hair-whorls. Parietal whorls which are considered to be normal scalp patterns could be a single whorl or double whorls. Cases of triple parietal whorls are less common.
Amar J. S. Klar conducted research to see if there was a genetic link between
handedness and hair-whorl direction. He found that 8.4% of right-handed people and 45% of left-handed people have counterclockwise hair-whorls. His research suggested that a single gene may control both handedness and hair-whorl direction.
[Human handedness and scalp hair-whorl direction develop from a common genetic mechanism. Klar AJS ''Genetics'' 2003 Sep 165(1):269-76 http://www.genetics.org/cgi/reprint/165/1/269.pdf]
However, Klar's research methodology in this and other studies has been questioned.
The direction of hair whorl is ''not'' consistent with
Blaschko's lines
Blaschko's lines, also called the lines of Blaschko, are lines of normal cell development in the skin. These lines are only visible in those with a mosaic skin condition or in chimeras where different cell lines contain different genes. These ...
.
Another result concerning handedness of the progeny of discordant
monozygotic twins
Twins are two offspring produced by the same pregnancy.MedicineNet > Definition of TwinLast Editorial Review: 19 June 2000 Twins can be either ''monozygotic'' ('identical'), meaning that they develop from one zygote, which splits and forms two em ...
suggests that left handed people are one gene apart from right handed people. Together, these results suggest (1) that a single gene controls handedness, whorl orientation, and twin concordance and discordance and (2) that neuronal and visceral (internal organs) forms of bilateral asymmetry are coded by separate sets of genetic pathways.
Animal behavioral theories
There are many (mostly apocryphal) theories concerning horse behavior and their hair whorls.
[Forsberg Meyer, Jennifer. "What's in a Whorl?" Horse & Rider June 2008: 46-53.]
One paper has suggested that abnormal hair whorls can be used to assess the likelihood of agitated behavior or
temperament
In psychology, temperament broadly refers to consistent individual differences in behavior that are biologically based and are relatively independent of learning, system of values and attitudes.
Some researchers point to association of temperam ...
in
cattle
Cattle (''Bos taurus'') are large, domesticated, cloven-hooved, herbivores. They are a prominent modern member of the subfamily Bovinae and the most widespread species of the genus ''Bos''. Adult females are referred to as cows and adult ma ...
in the auction ring.
A note on hair whorl position and cattle temperament in the auction ring
/ref>
See also
* Hairy ball theorem
The hairy ball theorem of algebraic topology (sometimes called the hedgehog theorem in Europe) states that there is no nonvanishing continuous tangent vector field on even-dimensional ''n''-spheres. For the ordinary sphere, or 2‑sphere, if ...
References
{{DEFAULTSORT:Hair whorl
Vertebrate developmental biology
Animal hair
Human hair