What factors contributed to the development of bipedal locomotion in humans?

There are a number of hypotheses about the development of bipedal locomotion in humans. The appearance in human ancestors of an S-shaped spine, a vaulted foot, an enlarged pelvis, a strong sacrum are hereditary changes that contributed to upright posture.
According to the hypothesis of Jan Lindblad, the ape-like ancestors of man were forced to climb on their hind limbs when searching for food in the water and when wading through water obstacles. Also, human ancestors were forced to climb down from trees to the ground due to climate and flora changes. To look for food in the tall grass, they had to get up from all fours on their hind legs.