Somatotype is a taxonomy developed in the 1940s, by American
psychologist William Herbert Sheldon, to categorise the human physique according to the relative contribution of three fundamental elements, somatotypes, named after the three
germ layers of
embryonic development: the
endoderm, (develops into the
digestive tract), the
mesoderm, (becomes
muscle,
heart and
blood vessels), and the
ectoderm (forms the skin and
nervous system). His initial visual methodology has been discounted as subjective, but later formulaic variations of the methodology, developed by his original research assistant Barbara Heath, and later Lindsay Carter and Rob Rempel are still in academic use.