Males are far more mesomorphic than females, meaning they have broader shoulders, a narrower waistline and a more muscular physique (Dixson, 2009). In fact, males are so much more muscular than females, that muscle makes up over 38% of their body composition, in comparison to just under 27% in females (Dixson, 2009). This additional muscle helps boys to be better adapted in physical tasks, such as hunting, fighting and lifting heavy objects. .
It has been found that women prefer more muscular men, to men who are slender or fat. This is likely to be because a muscular physique indicates that a man is strong, healthy and fit. Evolutionarily this is something that women would have wanted in their mating partners, so that they could protect them, feed them and allow for greater reproductive success (Dixson, 2009). Because females prefer these more muscular, mesomorphic males, they are far more likely to find mating partners, and therefore reproduce and pass on their genes to their offspring. Female's preference for more muscular men therefore indicates that inter-sexual selection has played a role in making the difference between male and female muscle composition greater. .
However, natural selection is also thought to have played a role in the development of a man's more muscular physique. In the traditional hunter-gatherer communities of our ancestors, it was most often the male's role to hunt for food. Hunting required the ability to run for long periods of time, a method known as "persistence hunting," which required a more muscular physique (Dixson, 2009). If men were incapable of hunting, and therefore incapable in providing themselves with food, it was unlikely that they would have survived –therefore the more muscular men, who were in fact capable of hunting, would have survived, reproduced and passed on their genes to their offspring. So the sexual dimorphic muscle size in humans has come about due to a combination of inter-sexual selection and natural selection.
