Editing Aggression (section)

====Challenge hypothesis====
The [[challenge hypothesis]] outlines the dynamic relationship between plasma testosterone levels and aggression in mating contexts in many species. It proposes that testosterone is linked to aggression when it is beneficial for reproduction, such as in mate guarding and preventing the encroachment of intrasexual rivals. The challenge hypothesis predicts that seasonal patterns in testosterone levels in a species are a function of mating system (monogamy versus polygyny), paternal care, and male-male aggression in [[seasonal breeder]]s.

This pattern between testosterone and aggression was first observed in seasonally breeding birds, such as the [[song sparrow]], where testosterone levels rise modestly with the onset of the breeding season to support basic reproductive functions.<ref name="Wingfield, John C., Ball, Gregory F., Dufty Jr, Alfred M., Hegner, Robert E., Ramenofsky, Marilyn 1987 602–608">{{cite journal |bibcode=1987AmSci..75..602W |title=Testosterone and Aggression in Birds |journal=[[American Scientist]] |volume=75 |issue=6 |pages=602–8 |last1=Wingfield |first1=John C. |last2=Ball |first2=Gregory F. |last3=Dufty |first3=Alfred M. |last4=Hegner |first4=Robert E. |last5=Ramenofsky |first5=Marilyn |year=1987 }}</ref> The hypothesis has been subsequently expanded and modified to predict relationships between testosterone and aggression in other species. For example, chimpanzees, which are continuous breeders, show significantly raised testosterone levels and aggressive male-male interactions when receptive and fertile females are present.<ref>{{cite journal |doi=10.1016/j.anbehav.2003.03.013 |title=Dominance, aggression and testosterone in wild chimpanzees: A test of the 'challenge hypothesis' |journal=[[Animal Behaviour (journal)|Animal Behaviour]] |volume=67 |pages=113–23 |year=2004 |last1=Muller |first1=Martin N |last2=Wrangham |first2=Richard W |s2cid=8041587 }}</ref> Currently, no research has specified a relationship between the modified challenge hypothesis and human behavior, or the human nature of [[concealed ovulation]], although some suggest it may apply.<ref name="Archer 319–345">{{cite journal |doi=10.1016/j.neubiorev.2004.12.007 |title=Testosterone and human aggression: An evaluation of the challenge hypothesis |journal=[[Neuroscience & Biobehavioral Reviews]] |volume=30 |issue=3 |pages=319–45 |year=2006 |last1=Archer |first1=John |pmid=16483890|s2cid=26405251 }}</ref>