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In the human anatomy, the chin is the lowermost part of the face. The area of the chin is known anatomically as the mental region. It tends to be more pointed and triangular in human females, while more square shaped in human males. 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. The elephant is the only other animal considered to display such a feature, although this leads to debate over the use of the term.
Whilst it is agreed that the chin emerged during the Middle and Late Pleistocene, its origin and biomechanical significance are the subjects of controversy. Prominent hypotheses include buttressing the jaw against stresses resulting from speech or chewing as well as simple sexual selection through mate choice. With the advent of more advanced computational facilities, finite element analyses have been used to support hypotheses involving mechanical stress. 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. It is possible that multiple causal factors have played a role in the evolution of this bony protuberance.
See also 
- ^ O'Loughlin, Michael McKinley, Valerie Dean (2006). Human anatomy. Boston: McGraw-Hill Higher Education. pp. 400–401. ISBN 0072495855.
- ^ Enlow, Donald H. (1982). Handbook of facial growth. Philadelphia: Saunders. p. 283. ISBN 0721633862. "In the human mandible, a prominent chin marks this region, a distinctive feature that characterizes the face of modern man (and also, for reasons yet to be studied, the elephant)."
- ^ Schwartz, Jeffrey H. (2000). "The human chin revisited: what is it and who has it?". Journal of Human Evolution 38 (3): 402. doi:10.1006/jhev.1999.0339. PMID 10683306. "When humans and elephants can both be described as having chins, it is probably time to reconsider the applicability of the term."
- ^ 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. doi:10.1016/j.mehy.2006.11.048. Retrieved 2012-12-22.
- ^ Daegling, David J. (1993). "Functional morphology of the human chin". Evolutionary Anthropology: Issues, News, and Reviews 1 (5): 170–177. doi:10.1002/evan.1360010506.
- ^ 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. doi:10.1002/ajpa.21330.
- ^ 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. doi:10.1002/ajpa.21447.
- ^ Wayman, Erin. "Why Do Humans Have Chins?". Smithsonian magazine — Hominid Hunting. Smithsonian Institution. Retrieved 2012-12-22.