There is considerable individual variability in penile size, however, and these measurements are not correlated with men's height or body weight. On average, the human penis is 15-16 cm long and 10-12 cm in circumference, during tumescence. Table 3.4 provides data on penile dimensions in several human populations, together with reliable measurements of penile lengths in the great apes. Human penile size and shape will then be discussed in comparative perspective.

Penile morphology is then considered in relation to primate mating systems and the possible effects of copulatory and post-copulatory sexual selection. In order to evaluate these hypotheses, I will firstly present data on penile measurements in human beings and in other primates. The human penis is displayed more prominently than those of other primates and this might be partly a result of sexual selection to enhance a visual signal of attractiveness or status (Short 1980 Diamond 1997). Female orgasm influences sperm retention and transport in relation to sperm competition (Fisher 1982, 1992 Small 1993 Baker and Bellis 1993a 1993b 1995 Miller 2000).Ĥ. Penile size and shape evolved to impart pleasurable stimulation to the partner during copulation, and to induce female orgasm. The human penis acts as a 'piston' during copulation and its size and distal morphology serve to displace and remove semen deposited during previous copulations, thus producing an advantage in sperm competition (Baker and Bellis 1995 Gallup et al. The length of the human penis has been selected to deliver sperm as close as possible to the female's os cervix during copulation, in order to gain an advantage in sperm competition (Smith 1984).Ģ. Four theories have been advanced to account for this:ġ. It is regrettable that exaggerated accounts of human penile size and shape have been used to bolster the proposition that sexual selection has moulded the evolution of the human genitalia and the psychological mechanisms that influence copulatory behaviour. None of these statements, and many others of a similar nature which pervade the published literature, is accurate, with the exception of the observation that the thickness of the human penis exceeds that of the apes. Miller (2000), in a book dealing with effects of sexual selection on evolution of the human brain, states that 'adult male humans have the longest, thickest and most flexible penises of any living primate'. semen coagulation ratings in primates, including H. Macaque Orangutan Gibbon Colobus monkey Gorilla Semen coagulation ratingįigure 3.18 Correlations between the rate of evolution of the semenogelin 2 gene, and A. Jolly (1999) states that a 'peculiarity of humans is that the penis is twice the size for body weight as that of any other primate.'

Baker and Bellis (like Smith) stressed that 'it is nearly twice as long and over twice as wide as that of the chimpanzee'. Smith (1984) regarded the human penis as 'extraordinary relative to the other hominoids'. It is an unfortunate circumstance that so many authors have applied hyperbole to descriptions of human penile morphology.

Gorilla penis length