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CONVERGENCE. “Embryologically, muscles that form the modiolus derive from a cellular concentration in the region of the second branchial arch. It is then logical to see these muscles converge to the corner of the mouth to form the modiolus, as they emerge from a common area.” http://europepmc.org/abstract/med/10783511 View in LinkedIn

GUT MICROBIOME AND DIETARY EXCHANGES. “Also, horizontal gene transfer between dietary bacteria and gut microbes can lead to the acquisition of new dietary capabilities by their hosts without requiring a change in the “species” composition of the gut microbiome.” (Another biggie). https://standardsingenomics.biomedcentral.com/articles/10.1186/s40793-016-0180-8 View in LinkedIn

NUANCED CONTROL. “These fine movements are related to a subcutaneous muscular structure termed modiolus, which is the meeting point of muscles involved in the motion of mouth and comparative anatomy shows this structure to be better defined in Man than in other primates.” https://lnkd.in/dg2kCaB View in LinkedIn

HORIZONTAL GENE TRANSFERS. “This kind of genetic exchange can occur between widely unrelated taxa.” (This is huge). https://standardsingenomics.biomedcentral.com/articles/10.1186/s40793-016-0180-8 View in LinkedIn

THE FACIAL MODIOLUS. “In facial anatomy, the modiolus is a chiasma of facial muscles held together by fibrous tissue, located lateral and slightly superior to each angle of the mouth. It is important in moving the mouth, facial expression and in dentistry.” https://lnkd.in/daNTbUH) View in LinkedIn

FLOATING GENE ISLANDS. “In some cases, horizontal gene transfer has become so common that it is possible to think of some “floating” genes more as attributes of the environment in which they are useful rather than as attributes of any individual bacterium or strain or “species” that happens to carry them.” https://standardsingenomics.biomedcentral.com/articles/10.1186/s40793-016-0180-8 View in LinkedIn

THE HUMAN SMILE. “Monkeys, imitators of man's gesture never shared smile with him and their facial expressions only result in grimaces. Study of animal anatomy may explain why subtle expressions of the lips are a more man's special gift than laughter.” https://lnkd.in/dg2kCaB View in LinkedIn

“THE NASOLABIAL FOLD varies considerably from person to person. Three main groups may be distinguished: convex, concave, and straight. It is the muscles of smiling that are directly responsible for the shape and depth of the fold, and in their absence of function, as in facial palsy, the nasolabial fold disappears.” (Laugh lines). https://lnkd.in/dGeUA-g View in LinkedIn

The exquisite anatomical analysis that has gone into this work is used daily in cosmetic surgery, and takes the crusty old Victorian anatomists working in the museum basement right into the modern clinic. Lovely stuff View in LinkedIn

SO ENDS this contemplation of what gives the human mouth and smile such a range of subtle expressions, and how these are lacking in other vertebrates, and how they arose during evolution. View in LinkedIn