Grades and Transitions in Human Evolution
Grades and Transitions in Human Evolution
This chapter assesses the number of grades that have appeared in the course of human evolution. It identifies three grades. The first is characterised by a species mean body mass of under 50 kg; a species mean stature of less than 150 cm; facultative bipedalism; relatively large teeth and jaws; a moderate size brain relative to body mass; and a relatively short period of maturation. The second grade is characterised by a species mean body mass of more than 50 kg; a species mean stature in excess of 150 cm; obligate bipedalism; relatively small teeth and jaws; a moderate size brain relative to body mass; and a relatively short period of maturation. The third grade is similar to the second in terms of body mass, stature, locomotor behaviour and masticatory system size; but exhibits a considerably higher level of encephalisation. It also exhibits delayed maturation.
Keywords: human evolution, facultative bipedalism, obligate bipedalism, masticatory system, encephalisation
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