There are many distinct hypotheses as to how and why bipedalism evolved in humans. all evidence points to bipedalism evolving before the expansion in human brain size. the different hypotheses are not necessarily mutually exclusive and a number of selective forces may have acted together to lead to human bipedalism. 1)postural feeding hypothesis 2)provisioning model 3)thermoregulatory model (heat based) 4)carrying models 5)wading hypothesis 6)turn-over pulse hypothesis 7)other behavioural models (there are a variety of ideas which promote a specific change in behaviour as the key driver for the evolution of hominid bipedalism. for example, wescott (1967) and later jablonski & chaplin (1993) suggest that bipedal threat displays could have been the transitional behaviour which led to some groups of apes beginning to adopt bipedal postures more often. others (e. g. dart 1925) have offered the idea that the need for more vigilance against predators could have provided the initial motivation. dawkins (e. g. 2004) has argued that it could have begun as a kind of fashion that just caught on and then escalated through sexual selection. and it has even been suggested (e. g. tanner 1981: 165) that male phallic display could have been the initial incentive.) pick one of these "theories" (or another that you find) then write a 1-2 paragraph summary of the theory. then discuss your opinion of the theory - do you find it plausible? do you think it is possible as the only reason why bipedalism evolved or must it be in conjunction with another selective pressure? make sure that you cite your sources correctly.