Share interesting facts about human body systems.

Understanding the Genetics of Widow's Peak Made Easy

Understanding the Genetics of Widow's Peak
The occurrence of a widow's peak in the hairline of an individual is often stated as an example for explaining simple genetic inheritance, where the allele producing this phenotype is dominant. Bodytomy explores and discusses the true genetic basis for the emergence of this v-shaped point in the hairline.
Komal B. Patil
Last Updated: Apr 9, 2018
Old Wives' Tale
In many cultures and communities, the presence of a widow's peak is considered an omen of early widowhood.
A widow's peak is a commonly occurring phenotype in the population. It refers to the presence of a v-shaped indent in the center of the hairline. Due to current hairstyle trends followed by men and women, it is not very easy to spot this particular phenotype. But its presence is evident and obvious if the person bearing it has their hair pulled back in order to expose the hairline. Individuals, who lack this feature, have straight and linear hairlines with no breaks in them.
Hairlines are formed due to the suppression of hair growth on the forehead. This hair suppression occurs due to bilateral pair of periorbital fields. The joining of these fields, forms the forehead and a straight hairline. In case of people with a widow's peak, the joining of these fields is not uniform, and hence, results in the characteristic peak. It has been theorized that this may be due to lowering of the point of intersection of the upper perimeter of these fields.

A similar hairline is observed in case of aging men with receding hairlines, but these are not true widow's peak. They are a mere pattern arising due to the senescence of hair follicles. The true feature is one that is exhibited on the hairline since birth.
The origin of the term can be traced back to the mid 19th century. It is believed to be coined after the characteristic beak or bill of a headdress donned by widowed women. This headdress was a form of hood with its front having a pointed piece, and was called the biquoquet. It was worn as a sign of mourning by widows. This hood had been in use since the year 1530, and earlier, was in the form of a mourning cap, called 'Mary Stuart Cap', featuring a triangular fold of cloth in the middle of the forehead.
Genetic Basis
Widow's peak is thought to be a good example for demonstrating simple dominance with respect to genetic inheritance. But, contrary to popular belief, this feature is not determined by a single gene but by multiple genes; hence, it does not follow simple dominance. Also, no supporting experimental data has been found to support the theory of a simple dominant inheritance for this trait.

Despite this, widow's peak occurs in populations, the way a dominant trait does. It has been observed that the possession of this type of hairline by any one of the parents, is often reflected in the hairlines of most of their offspring. This could be explained if the trait is produced as a result of a defect in the genes regulating the proper intersection of the bilateral periorbital folds. In such a case, the defect could be passed down to the progeny without it being recognized by the DNA repair machinery, thereby, producing a widow's peak in the progeny. In the event that the gene defect or aberration is identified and rectified by the DNA repair mechanisms, the progeny would be born with straight hairlines. This provides an explanation for the cases where both parents possess a widow's peak but their child has a straight hairline.

However, no concrete explanation can be given for the presence and inheritance of this trait due to the lack of any reliable experimental data. There have been only two noteworthy studies regarding this trait, but the results do not match. The 1973 study, conducted by Smith and Cohen on male medical students, found that only 3% of the total number of students possessed this trait; whereas, the 2009 study, carried out by Nusbaum and Fuentefria on women, found that 81% of these women possessed this trait. The large discrepancy between these findings suggests extremely high gender-specific variation, or that the two groups of investigating scientists had completely different perceptions of what constitutes a widow's peak.
Clinical Presentation
While a majority of people exhibiting a widow's peak show no developmental and health disorders, few syndromes exhibit this phenotype as part of their symptoms. In 1973, David W. Smith and M. Michael Cohen hypothesized that the trait was observed due to a lowered point of intersection of the periorbital folds, and that this lowering was due to the folds being widely spaced. This associated the widow's peak trait with ocular hypertelorism (eyes are far apart). Based on this line of thought, the occurrence of this trait was investigated in conjugation with other disorders and syndromes by many researchers. Their efforts have led to the identification of this trait as being one of the symptoms in a diverse range of genetic disorders such as the Donnai-Barrow syndrome (caused by mutations in the LRP2 gene), Waardenburg syndrome, Aarskog syndrome, Opitz-Frias syndrome, and frontonasal dysplasia.
People and Characters with Widow's Peak
Various fictitious characters have been portrayed as having a widow's peak, and this trait has often been associated with villainous intent of an antagonistic character. Few examples of characters possessing this trait are as follow:
►Count Dracula
Count Dracula
Superman Hero
►Vegeta (Dragon Ball franchise)
Vegeta Dragon
►Eddie Munster

►The Joker (Batman franchise)

►Hannibal Lecter
Notable and famous real life examples of people possessing this hairline trait include celebrities such as:

►Marilyn Monroe
►Gene Kelly
►Geena Davis
►Nicole Kidman
►Blake Lively
►Elvis Presley
►Chris Hemsworth
►Keanu Reeves
►John Travolta
►Leonardo DiCaprio
In conclusion, since there is no experimental data suggesting or disproving the genetic basis for the inheritance of the widow's peak, it should not be used as an example for simple genetic inheritance. In addition, this trait is merely a physical anomaly, and hence, should not be misinterpreted as an omen.