The genetic origins of human scalp hair whorls have been explored in a groundbreaking study, revealing that their orientation is influenced by multiple genes rather than a single one, as previously believed.
This discovery, published in the Journal of Investigative Dermatology, pinpoints four specific genetic variations associated with the direction of hair whorls.
Hair whorls are circular patterns of hair growth that revolve around the orientations of hair follicles . These patterns are characterized by the number of whorls (single or double) and their directional movement (clockwise, counterclockwise or scattered).
Understanding the genetic foundation of these whorl patterns is significant, given their link to irregular neurological development. By delving into this matter, the study initiated a genome-wide association study (GWAS) involving 2,149 Chinese participants from the National Survey of Physical Traits. This was then reinforced by a replication study encompassing 1,950 individuals from the Taizhou Longitudinal Study.
Dr Sijia Wang, the Chinese Academy of Sciences lead researcher, explained that their primary goal was to uncover the genetic underpinnings behind intriguing physical traits. These traits encompass hair whorls and other characteristics such as fingerprint patterns, eyebrow thickness, earlobe shape and hair curliness.
Traditionally, it was believed that a single gene controlled the direction of hair whorls following Mendelian inheritance principles . However, the study’s findings deviate from this notion, revealing that multiple genes collectively contribute to the orientation of hair whorls, suggesting a polygenic inheritance model.
The study identifies four distinct genetic variations (situated at 7p21.3, 5q33.2, 7q33, and 14q32.13) that are likely to impact the direction of hair whorls. These genetic components exert their influence by regulating the polarity of hair follicle cells, potentially affecting the closure and growth of the cranial neural tube.
Dr Wang emphasized that while previous theories had suggested connections between hair whorl patterns and abnormal neurological development, the study did not establish significant genetic links between the direction of hair whorls and behavioral, cognitive, or neurological traits.
Even though much remains to be uncovered about the intricate aspects of human appearance, the researchers are confident that their curiosity-driven endeavors will eventually unveil the answers they seek .
Learn more about the study published in the Journal of Investigative Dermatology.