Comparative anatomy of Man and Apes

Darwin's declaration regarding the descent of man from non-human ancestors caused a great deal of controversy among the scientists and the general public of those times. It was a matter of great degradation when any attempt was made to draw any line of relation between Man and Apes. However, in due course, with newer inventions and discoveries in this area, Darwin�s views were accepted by all and thereby the people were forced to embrace their strange relatives.

Apes and Man are members of family Pongidae, Hylobatidae and Hominidae. The belong to the suborder Anthropoidea and the order Primates. The relationship of apes and man will be understood if attempts are made to study the various anatomical features critically.

Skull

The skulls present many contrasting features such as:

In Man

1. The skull of the man is highly developed in the frontal region.
2. The forehead extends almost vertically in upward direction.
3. The supra-orbital ridge is not so developed.
4. No sagittal crest is present in the skull.
5. The maxilla and pre-maxilla have been fused.
6. Foramen Magnum is situated at the center of the skull.
7. The head is well balanced hence the face is perfacttly vertical

In apes

1. The forehead is less developed and head slopes backward
2. The supra orbital is highly developed
3. Sagittal crest is present in the skull
4. Foramen magnum is seen further backward at the base of the skull, it is for this reason that the face of apes hangs downwards.

Mandible

In Man

1. The lower jaw in man is small in size in comparison to those of apes
2. The muscle responsible for the movement of lower jaw is weak
3. In man there is always a well developed chin
4. Prognathism is absent

In Apes

1. Ape's lower jaw is massive
2. There is no trace of chin
3. Muscles for movement of lower jaw are strong
4. Facial prognathism is very common among apes.

Teeth

In Man

1. Smaller in size than those of apes
2. Canines do not project forward beyond the level of other teeth
3. Chewing motion is side to side and also up and down known as rotary motion
4. Dental arch takes the shape of a parabola

In Apes

1. Dental arch is U shaped
2. Size of teeth are large
3. Canines projects beyond the level of other teeth, due to this nature canine of apes interlock when jaws are closed
4. This arrangement prevents the lateral movement in chewing so only up-down chewing motion is present.

Nose

In Man

1. Nose is well developed
2. The root and bridge of the nose have a slightly marked elevation
3. Tip of the man has a thick bulb
4. The nasal wings are strongly developed

In apes

1. Nostrils are smaller and generally pointed downwards
2. The elevation at the root and bridge is very little or absent
3. Tip of the nose is lacking in apes
4. The cartilaginous portion of the nose is very wide unlike man and it is little raised on the surface of the face

Lips

1. Integumental upper lip shows a median furrow which starts from nasal septum and continues up to the edge of the membranous lip. Median furrow is characteristics feature of Man.
2. The lips of the apes are seen starched over their bulging jaws and they are loose and protrusive.

The apse lips are thin and the red portion of the lips are rarely seen when mouth is closed. The integumental lip has little quantity of fat.

Arms

In apes the arms are greatly elongated, an adaptation to the habit of hanging and walking in branches. In apes upper arms act as movable levers and hence the length is short and in man lower arm is movable lever and hence shortened.

Legs

The femur (Thigh Bone) of ape is short, thick and curved. In man it is long slender and elongated. The ridges for muscle development in femur are greatly developed in man than in the apes. The linea aspera, a rough ridge on the back side of the femur is characteristics to the man.it has resulted due to great development of of the extensor muscle which play a important part in erect posture and the bipedal gait.

Foot

• The foot of man has witnessed a remarkable change due to its new mode of locomotion. The foot supports the weight of the body and helps in walking and standing erect.
• In apes the foot is used both for locomotion and grasping of the tree branches.
• The great toe in man is not opposable.
• The lateral toes are reduced in size and the fifth one rudimentary.

Brain

Brain in man is not only much larger than that of apes but also highly developed. The weight of man�s brain is three times as heavy as that of a gorilla, the largest ape. The frontal region of the human brain is especially developed and the cerebral cortex presents a much more complex development than that of the apes.

The brain case in the man is largest ranging from 1300 to 1450 cc. the average cranial capacity of gorilla is 549, chimpanzee 400, orangutan 416 and gibbon 98 cc respectively.

Speech

Man is distinguished from the apes mainly by his ability of articulating speech. But there are some scientists who has felt that the use of some sort of language among apes.

Anatomical Similarities along with dissimilarities between MAN & APE

A. Gorilla and Man:

In hands, feet and pelvis along with size of brain the gorilla shows close relationship with man. But the massive jaws of the gorillas have no resemblance with those of man.

B. Chimpanzee and Man:

Their resemblance covers the likeliness of the skull and pigmentation of the body. The chest portion of the Chimpanzee is almost human.

C. Orangutan and Man:

In his high forehead and the same number of pair of ribs the orang shows similarities with man. On the other hand , two factors like the shortness and degenerate character of the legs and The adaptation of the feet for suspension, separate these two individuals from each other.

D. Gibbon and Man:

The length of leg and the erect gait of the gibbon indicates its closer relationship with man, anatomically.

But in other characters like excessive arm lengths, general size, pelvis, hands and feet, length of canine teeth and the size of brain, the gibbons goes farthest from the man.

Among the four apes it is seen that each of them have developed one or more special features, with which it can demand as closest relationship with Man.

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