Current events Lia Queiroz do Amaral Department of Applied Physics, Institute of Physics, University of Sa ˜o Paulo, C.P. 66318, 05389-970—Sa ˜o Paulo, SP, Brazil Loss of body hair, bipedality and thermoregulation. Comments on recent papers in the Journal of Human Evolution Journal of H uman Evolution (1996) 30, 357–366 Introduction A series of papers by Wheeler (1984, 1985, 1990, 1991a,b, 1992a,b, 1993, 1994a) have been published in the Journal of H uman Evolution on the subject of the thermoregulatory advantages of hominid bipedalism combined with naked skin and larger body size. The premise of these papers, regarding loss of body hair, is that it occurred only when biped hominids moved to open savanna environments. These papers have already attracted commentary from Dean (1988, 1990), Porter (1993) and very recently Chaplin et al. (1994), with reply by Wheeler (1994b). Although it is widely accepted that naked skin facilitates dissipation of body heat, the circumstances favoring its evolution are quite unclear. The point made in this paper is that although Wheeler’s calculations demonstrate the thermoregulatory advantages of bipedalism over quadrupedalism and of increased body size in savanna environments, the results do not indicate that the initial step in the denudation process occurred in open hot environments, nor that bipedality preceded body-hair reduction. Most of the points analyzed by Wheeler in his detailed calculations had been considered with rougher estimates in an earlier paper by Newman (1970), not mentioned by Wheeler. In his analysis, Newman concluded that ‘‘the obvious time and place where progressive denudation would have been least disadvantageous is the ancient forest habitat’’. It is argued here that Wheeler’s more detailed calculations give support to such a very early process of denudation and not to its later evolution in equatorial savanna environments. In his first papers (Wheeler, 1984, 1985) Wheeler claimed that ‘‘the lower direct solar radiation fluxes incident upon a biped mammal made possible the reduction of body hair’’. That is, bipedalism would be pre-adaptive to loss of body hair. But his calculations, regarding estimates of the percentages of total body surface area exposed to direct solar radiation, only showed advantages of bipedalism in relation to quadrupedalism, without any consideration as to the question of denudation. He did not tackle the crucial point: a haired biped could be a better choice regarding thermal stress from direct solar radiation. In later papers (1991a,b, 1992a) arguments supporting the advantages of larger body size and lower water requirements of bipeds are shown in calculations made for haired bipeds and quadrupeds. But no consideration was given to the question of nakedness. It was only in the next paper (1992b) that Wheeler really addressed the question of loss of body hair, making calculations for haired vs. naked bipeds and quadrupeds, crossing the four alternatives. Therefore, focusing on this paper is appropriate. 0047–2484/ 96/ 040357+ 10 $18.00/ 0  1996 Academic Press Limited