Updated 26th of December 2021
The chin has many scientific names: mental eminence, mental protuberance, mental osseum, and tuber symphyseos. The human chin has a size between 0.7 cm and 1.1 cm in a fully developed adult.
One of the characteristics of the evolution of humans is to have a well-developed chin. Compared to primates or other human ancestors, including Neanderthals, Homo sapiens have a unique chin shape that brings it more forward.
It is unclear why a prominent chin was an evolution advantage. Some scientists say that such chins resist more to masticatory stress. Others argue that the faces of Homo sapiens became smaller as they evolved, exposing the bony prominence at the lower jaw.
The chin is made up of an eminence (or protuberance) which forms a triangle with a clearly widened base, delimited by bumps or protrusions located on the sides of the chin eminence, which are called the chin tubercles.
In humans we notice a sexual dimorphism of the chin, which results in anatomical differences between males and females. Men tend to have a square jaw and a small chin (associated with a greater production of testosterone), while women have a thinner lower face and a more pronounced chin. According to an anthropological study spanning over the past 80,000 years, the facial characteristics of modern men would have feminized, tending towards a more prognathic jaw and a more prominent chin. This phenomenon is linked to the general drop in testosterone levels in men, as they developed social interactions described by less violence and more tolerance.
A cleft chin refers to a chin with a Y-shaped dimple (or fissure) in the middle, with a particular underlying bone shape. Specifically, the chin fissure follows the fissure in the lower jawbone. This happens when the two sides of the lower jaw are incompletely fused together during the development of the fetus. For other people, a cleft chin can develop over time, often because one half of the jaw is longer than the other, leading to facial asymmetry.
There is little scientific information of hereditary causing a cleft chin. But it is a trait shared among members of the same family. There are also many chins that have an intermediate shape between smooth and clearly cleft.
Aside from the dimple, a cleft chin doesn’t cause any other symptoms.
Removal surgery is possible for people who want to have a smoother chin. The surgery consists of either removing the cleft chin or just reducing the size of the fissure. Surgery is also possible to create a cleft chin.
A double chin is a loss of definition of the jawbone or soft tissue under the chin, forming wrinkles that give the impression that there are two or more chins. Double chin may be found in babies, overweight people, and the elderly.
There are two possible causes for a double chin:
- For people that are overweight, the fat under the skin that is located around the neck, tends to sag down into a wrinkle, that gives the appearance of a second chin. In this case, the fat pad can be removed surgically and at the same time the associated muscles under the jaw are shortened.
- another cause of a double chin can be a bony deficiency, commonly seen in people of normal weight. When the mandible (lower jawbone) doesn’t project forward enough, the chin in turn will be underdeveloped. Despite that there’s little fat in that region, it can appear as if the chin is melting back into the neck.
Also called mentoplasty, genioplasty is the surgical reduction of the chin, that can be used in several situations: to move the chin forward, to move it backward, to move it sideways in a case of asymmetrical chin, or to move it vertically to give the appearance of a longer or a shorter chin.
There are two types of genioplasty:
- Sliding genioplasty, where the bone of the chin is cut away from the jaw so it can be displaced either forward (cases of short chins, or chins to the back), backwards (cases of chins that are too long or too much forward), or vertically to make the chin look longer or shorter.
- Chin implants can be placed either surgically or by injection, using different material (plastic, synthetic materials, or fillers), to correct the appearance of the chin by pushing it forward.
- N. E. Holton, L. L. Bonner, J. E. Scott, S. D. Marshall, R. G. Franciscus, T. E. Southard. (The ontogeny of the chin: an analysis of allometric and biomechanical scaling). Journal of Anatomy June 2015 – Volume226 – Issue6 – Pages 549-559.
- T Abraham. (Numerical Survey of the Different Shapes of Human Chin). Journal of Craniofacial Surgery: September 2013 – Volume 24 – Issue 5 – p 1657-1659.
- P Picq, P Bronot. Le Sexe, l’Homme et l’Évolution. Odile Jacob, 2009, p. 87.
- R L Cieri, S E Churchill, R G Franciscus, J Tan and B Hare, Craniofacial Feminization, Social Tolerance, and the Origins of Behavioral Modernity, Current Anthropology, vol. 55, no 4, août 2014, p. 419-443.
- ScienceDaily, (Why we have chins: Our chin comes from evolution, not mechanical forces).
- McGill University – Office for Science and Society, (Why Do We Have Dimples?).
- HealthLine, (Cleft Chin Surgery).
- HealthLine, (Genioplasty (Chin Surgery)).
- Wikipedia, (Chin).
- Wikipedia, (Chin augmentation).
The information above should be used as a reference only. Any medical decision should not be taken before consulting a health care professional.