Chin or mental region labeled in purple
Latin Mentum
Inferior alveolar artery
Mental nerve
MeSH A01.456.505.259
Anatomical terminology

The chin or the mental region is the area of the face below the lower lip and including the mandibular prominence.[1] It tends to be smaller and more rounded in human females, while bigger and more square in human males.[2] It is formed by the lower front of the mandible. In humans there is a wide variety of chin structures, e.g. cleft chin.

The chin developed as a point of muscular attachment facilitating minute movements of the lips associated with speech. In human evolution, the chin is a cladistic apomorphy, partially defining anatomically modern humans as distinct from archaic forms. Non-human anthropoid apes have a simian shelf for example. Elephants are the only other animals considered to display such a feature,[3] although this leads to debate over the use of the term.[4]

The chin emerged during the Middle and Late Pleistocene, but its origin and biomechanical significance are the subjects of controversy.[5] Prominent hypotheses include buttressing the jaw against stresses resulting from speech[5] or chewing[6] as well as simple sexual selection through mate choice.[7] With the advent of more advanced computational facilities, finite element analyses have been used to support hypotheses involving mechanical stress.[8] On the other hand, increased availability of data regarding sexual dimorphism in chins has also lent support to the sexual selection hypothesis as sexual dimorphism is more difficult to explain under other regimes.[7] It is possible that multiple causal factors have played a role in the evolution of this bony protuberance.[9]

See also


  1. ^ "Full Definition of chin".  
  2. ^ O'Loughlin, Michael McKinley, Valerie Dean (2006). Human anatomy. Boston: McGraw-Hill Higher Education. pp. 400–401.  
  3. ^ Enlow, Donald H. (1982). Handbook of facial growth. Philadelphia: Saunders. p. 283.  
  4. ^ Schwartz, Jeffrey H. (2000). "The human chin revisited: what is it and who has it?". Journal of Human Evolution 38 (3): 402.  
  5. ^ a b Ichim, Ionut; Jules Kieser; Michael Swain (2007). "Tongue contractions during speech may have led to the development of the bony geometry of the chin following the evolution of human language: A mechanobiological hypothesis for the development of the human chin". Medical Hypotheses 69 (1): 20–24.  
  6. ^ Daegling, David J. (1993). "Functional morphology of the human chin". Evolutionary Anthropology: Issues, News, and Reviews 1 (5): 170–177.  
  7. ^ a b Thayer, Zaneta M.; Seth D. Dobson (2010). "Sexual dimorphism in chin shape: Implications for adaptive hypotheses". American Journal of Physical Anthropology 143 (3): 417–425.  
  8. ^ Gröning, Flora; Jia Liu; Michael J. Fagan; Paul O'Higgins (2011). "Why do humans have chins? Testing the mechanical significance of modern human symphyseal morphology with finite element analysis". American Journal of Physical Anthropology 144 (4): 593–606.  
  9. ^ Wayman, Erin. "Why Do Humans Have Chins?". Smithsonian magazine — Hominid Hunting. Smithsonian Institution. Retrieved 2012-12-22.