Sexual bimaturism explained

Sexual bimaturism describes a difference in developmental timing between males and females of the same species. Sexual bimaturism can result in sexual dimorphism, but sexual dimorphism could also develop through differential rates of development. In many insects, the larval period of females is longer than that of males, and as a result of this extended growth period, these female insects are larger than their male conspecifics.[1] Male simian primates are generally larger than females of the same species due in part to extended growth periods.[2] Gorillas demonstrate a particularly high degree of sexual bimaturism.[3]

Bimaturism can refer to developmental differences within a sex related to secondary sex characteristics. For example, male orangutans reach sexual maturity around age 15 but undergo an additional period of development later in life before they exhibit cheek flanges. Flanged males are generally preferred by females so that unflanged males need different mating strategies to compete with flanged males.[4] [5] The onset of this second developmental phase varies greatly and may be influenced by the proximity of other flanged males.[6]

In humans, sexual bimaturism is evident in that males begin puberty later than females. This may be related to selection for later maturation in males in a polygynous mating system.[7]

Notes and References

  1. Teder. Tilt. Sexual size dimorphism requires a corresponding sex difference in development time: a meta-analysis in insects. Functional Ecology. 2014. 28. 2. 479–486. 10.1111/1365-2435.12172. free.
  2. Leigh. Steven R.. Patterns of variation in the ontogeny of primate body size dimorphism. Journal of Human Evolution. 1992. 23. 1. 27–50. 10.1016/0047-2484(92)90042-8.
  3. Shea. Brian T.. The ontogeny of sexual dimorphism in the African apes. American Journal of Primatology. 1985. 8. 2. 183–188. 10.1002/ajp.1350080208. 31986820 . 85730045 .
  4. Web site: Askew. James. Call of the Orangutan: An Ape Named James. Scientific American Blogs. Scientific American. 19 July 2015.
  5. Utami. Sri Suci. Goossens. Benoit. Bruford. Michael W.. de Ruiter. Jan R.. van Hooff. Jan A.R.A.M.. Jan van Hooff. Male bimaturism and reproductive success in Sumatran orang-utans. Behavioral Ecology. 2002. 13. 5. 643–652. 10.1093/beheco/13.5.643. free.
  6. Maggioncalda. Anne N.. Sapolsky. Robert M.. Robert Sapolsky. Czekala. Nancy M.. Reproductive hormone profiles in captive male orangutans: Implications for understanding developmental arrest. American Journal of Physical Anthropology. 1999. 109. 1. 19–32. 10.1002/(SICI)1096-8644(199905)109:1<19::AID-AJPA3>3.0.CO;2-3. 10342462.
  7. Web site: Barash. David. Early Girls, Slow Boys. The Chronicle of Higher Education Brainstorm. The Chronicle of Higher Education. 19 July 2015.

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