The Role of Hairs in the Biological Evolution of Humans pp. 187-196
Authors: (Lia Queiroz do Amaral, Department of Applied Physics, Institute of Physics, University of São Paulo, Brazil)
Abstract: The characteristics of human hairs are connected to the unique evolution of human skin, which constitute a difficult biological problem, of no trivial solution. A recent provocative proposal that brings some new light on the enigma of human biological evolution is focused. The role of hairs as support for infant clinging in primates is analyzed, together with the mechanics involved in the forms of infant carrying in primates. Data on tensile properties of human and ape hairs and values for the forces at the elastic limit as well as the friction coefficient are discussed. The limits connected with infant weight are defined both for clinging to hairs and for the mounting position of primate infants on the adult primate body. It is shown that bipedalism is incompatible with the usual primate pattern of infant carrying. This leads to the proposal of emergence of bipedalism as a unique solution for infant carrying in the human lineage.