Human beings evolved from non-human primates. The continuous and ongoing advancement from the terrestrial quadrupedalism i.e. pronograde to semi-erect posture i.e. clinograde, and lastly to a completely erect posture i.e. orthograde with bipedal locomotion is the method of the advancement of locomotion from simians to the man which has been taken. The man stands with a vertical back, straight legs, and hanging arms and hands. Furthermore, when a man could walk bipedally and erect standing straight, then only he could be referred to as a man.

Changes in Pelvic Girdle Because of the Assumption of the Erect Posture

When a man erects while standing, the weight of the body of the man is to be spread on the hind legs through the pelvic girdle. Hence, the pelvis acts as an essential part in getting an erect posture and has had naturally gone through numerous changes. Notably, the pelvis transformed rather more than the vertebral column during the process of advancement of erect posture as well as bipedal gait i.e. Buettner Janunsch.

Few Associated Changes:

• The pelvis may be similar to a bony cylinder that is flat from side to side, with the long axis in it that is parallel to the spine, and the spine parallels with the ground, among the quadrupeds.
• Whenever an animal stands up, and its spine is more or less perpendicular to the ground, then the girdle transmits the entire bodyweight of the animal. This new stress results in the pelvis being flattened towards the downside and expanded laterally; therefore, it turns out to be lower as well as broader at the same time. Furthermore, this results in spreading out of its anterior end or superior end, making it look like a funnel in shape with a tiny orifice towards the downside.
• There was an observation that the human pelvis had been through a mosaic evolution. The three bones making up the pelvis: ischium, ilium, as well as pubis didn’t change or evolve at an equal rate.
• The ilium went through the most change, and the ischium went the least change. The man’s ischium is nearly equal with the ischium of living Pongidae i.e. ‘Washburn’. The ilium became short as well as broad at the same time and bent backwards on the ischium; therefore, it resembles a fan-type shape. Among the primates, the high-level tininess of the human ilium sets man in a position of the lower pelvis relative to the height of a trunk than any different primate.
• The extreme and too much breadth of the sacral part of the ilium of a human also assists in the process of dividing and spreading the whole weight of the human body.
•  Ilium’s ilio-sacral articular surface is located extremely above the acetabulum in the other primates; as such no bony structure reverse of the acetabulum is there. When we talk about a man, the lower portion of the sacrum is just the reverse of the acetabulum.
• Respectively, the pelvis of the human exhibits a far bigger as well as thicker acetabular area as compared to the region of other primates. In addition, it assists in the process of spreading as well as supporting the bodyweight of the femur.

Changes in Femur because of the Assumption of the Erect Posture

• While comparing with other primates, the legs of human beings are longer as compared to their arms, as such the femur is lengthier as well as stout.
• The condyles are bigger compared to other non-human primates because the leg’s joints need to have a huge and stout structure that helps in supporting the bodyweight. 
• The ridges for the attachments of muscles in the femur are defined much sharply as well as distinguished from other non-human primates.

Changes in Foot because of the Assumption of Erect Posture

• The hind limb is not a grasping organ anymore but a locomotory organ with the assumption of the bipedal walk as well as the erect posture.
•  The supporting metatarsal bones of the great toe, as well as the toe itself, must be brought into the line of the foot’s long axis; for a divergent toe, therefore, all the toes are arranged in a line.
• The giant toe is not opposable anymore since the foot as a whole is not a grasping body part. And due to this, it also turned out to be smaller as compared to the thumb.

Conclusion

The erect posture implications conclude that there are and there can be various complications of the erect posture in human beings as compared to some other non-human primates. We have discussed some of the dissimilarities and changes.