Kim Kardashians Of The Wild

1452 Words6 Pages
Kim Kardashians of the wild? Exaggerated sexual swellings in non-human primates: mechanisms and functions
Oedemas of sexual tissue with extracellular water retention and swellings of the skin of the circumanal, subcaudal and paracallosal regions (Krohn & Zuckermann, 1937; Dixson, 1998a) are observed in many species of non-human primates, baboons being famous for their large bright behinds. We know that this engorged feature has evolved independently 5 times as different tissue areas are involved in each of the species exhibiting the trait (Dixon, 1998b). Multiple independent evolutions of this trait suggests that the exaggerated swellings serve an adaptive purpose. (Tecumseh Fitch, 2011) The possibly quite significant added costs of simply
…show more content…
Analysis on faecal matter showed that turgescence of baboon ano-genital swellings links to the follicular phase of the ovarian cycle, while deturgescence links to the luteal phase, leading to the conclusion that the swellings are under the influence of hormonal control in primates (Gillmann and Gilbert, 1946). This suggests that the role of sexual swellings is to visually indicate the onset of ovulation to male non-human primates. It is observed that swellings indeed attract males independently of olfactory or behavioural cues (Bielert 1982; Saayman 1970) suggesting evolution of this attraction to larger swellings occurred due to the reproductive success associated with it. Males that are able to recognise swellings, discriminate between them and to mate with the female when hers are largest, would have higher chances to sire an infant, resulting in high selection pressure on males to react to swelling state.
Ulterior motives
Examples have been found where swellings also occur in other situations where ovulation is highly unlikely. For example in chimpanzees (Wallis, 1972) tumescence was observed in an irregular pattern throughout pregnancy, and in Sooty Mangabeys a swelling virtually identical in size to maximum conception swelling was observed consistently in the first trimester. (Hadadian & Bernstein, 1979) This
Open Document