Question

What are the physical changes that resulted in upright posture in the course of evolution of humans?

Answer 1

Hint: Upright posture is erect posture and this helped in bipedal locomotion. Apes and the initial man showed quadrupedal locomotion.

This change was important as the upper limbs are available for different functions and not for walking.

Complete Answer:

Human Evolution is related to Evolution of Apes. Thus this can be studied under three main headings:

(1) Prior to Ape Men

(2) Ape Men including prehistoric Men

(3) True Men including Modern Men 

Thus from Apes to Modern Man, there have been changes in physical appearance as well as brain capacities also.

(1) Prior to Ape Men includes  (pithecus is apes)

- Proconsul

- Dryopithecus

- Ramapithecus

- Sivapithecus

- Kenyapithecus

(2) Ape-Men includes

- Australopithecus (link between Ape and Man)

- Homo habilis (Homo is man)

- Homo erectus

(3) True men includes 

- Homo sapiens neanderthalensis

- Cro Magnon man

- Homo sapiens sapiens (The Modern Man)

The main physical feature that can be seen in the evolution from Apes to Man is the erect posture that has evolved gradually. The changes seen are as follows:

- Backbone developed from arched shape (C shaped) to S shaped. Due to this there is a forward curve in cervical and lumbar region and backward curve in thoracic region. It improves the stability and balance of the body.

- The shape of the pelvic girdle changed from narrow and elongated to broad and shallow. The Gluteus muscles (hip muscles) also strengthened . These allowed the weight of the body to directly transmit to the legs. 

- The Centre of gravity changed from the centre of the spine to the lower back area.

- The femur (thigh bone) and the knee are angled inwards and thus these are closer to the centre of gravity. This allowed to extend the knee joint and also improved the weight bearing capacity

- The foot has a non-opposable big toe (unlike the hand). This allowed humans to walk forward easily. 

- The head is exactly at the top of the spine. This is due to the change in position of the foramen magnum (this is an opening through which the spine begins). It changed from the rear side to the base of the skull

Note: The above changes also have some disadvantages in humans but the erect posture helped man to become independent and thus  man evolved in other fields and thus played a major role in overall development.