WHY DO THE TESTES HANG AT DIFFERENT LEVELS IN HUMAN MALES? There are papers published on this mostly concerned with thermoregulation. However in my opinion the probable answer to the testes question is in that position the testicles take up less sideways space between the thighs in a bipedal posture in which the thighs are placed closer together underneath the trunk for support. Good evidence for that theory is that the different level effect is much more pronounced in bipedal humans where there is less space for the testes to hang due to the upright posture than in males of other quadrupedal species where there is less space restriction.
WHY DO ONLY HUMANS COMMIT SUICIDE?