Comparative anatomy of man and apes.

Differences due to locomotor pattern:

1). man is erect bipedal whereas apes are basically tree dwellers with brachiation as the main locomotor pattern.large apes such as male gorilla take to trees for food and sleeping and seldom takes to brachiation. on the ground orangutan performs palm and fist walking and gorilla and chimp performs knuckle walking.both patterns being varients of quadrapedalism.

2). in man are present four curves in spinal column. cervical, thoracic, lumbar and sacral. the first and the third being acquired in the childhood whereas the second and fourth being congenital.apes lack such curves of spinal column. man, thus can stand erect habitually apes not.

3). in man, vertebrae of the spinal column show progressive increase in the size so that it is conical in out line. a conical spinal column can bear load of head much efficiently. Not so in apes.

4). Thoracic basket in apes is expanded hence centre of gravity lies much away from the long axis of the body.in man,thoracic basket is compressed so that centre of gravity of human pass through their foot.

5). in man forearms is shorter than legs,the latter support the body.in apes forearms are larger than legs which, together with forearms supports the body.

6).ilium of pectoral girdle is basin type in man to support internal organs against gravitational pull. in apes, ilium is elongated. anthropoidal plate and extension of ilium is shorter in apes but extended in man.

7).the spinal column-pelvis axis is closer to pelvis femur axis for smooth transference of the weight of body in man.not so in apes.

8). in man,neck of femur makes large angle with the axis of shaft so that it articulates with the pelvis laterally and allows all round movement of the leg. In apes, femur is short thick and its neck does not make great angle with its shaft.thus an apes lack perfect erectness and bipedally.

9). in man, linea aspera is greatly developed but not so in apes.linea aspera, at the back of femur provides attachement surface for the muscles that helps in erect posture.

10).in man, foot with adaptation for erect posture calcaneum formingheel, metatarsals held closely by transverse ligaments, hallux or great toe or big toe non opposable and doubly arched foot are some of the adaptations of human foot for bipedalism. apes have their heels poorly developed and foot without arches.their toes are longer than man’s and load line is in the centre.

11).development of leg thigh and hip musculature in man has reached a stage that facilitates upright standing,striding walk andrunning. hip muscles gluteus maximus gluteus medius amd gluteus minimus are well developed for stabilizing pelvis during walk.

Difference due to dietary habits.

1).in apes incisors are broad spatula-like that makes the jaw broad u shaped. In man small incisors make the dental arcade smooth rounded parabola.

2). in apes, canines are large projecting above the level of other teeth,the lower canines fitting into a gap,simian gap or diastema, between lateral incisors and canines of upper jaw.the canine interlocking in apes,thus ,allows only vertical motion of the jaws whereas the motion is rotatory in man.

3). in apes, the first lower premolar is sectoral.

4). in apes, molars have conical cusps(5 in lower molar) separated by characteristic arrangements of intervening groves.human molars have low blunt cusps adapted for crushing by rotatory motion.

5). simian shelf is present in apes but absent in man.

6). in apes face is prognathous without chin. In man face is orthognathous with chin.

7). sagittal crest and spra orbital ridges in the skull well developed in apes for attachment of jaw muscles.

Differences in hand structure.

1).in apes hand is utilized for locomotor purposes. in brachiation the fingers form a hook. Thumb, though opposable, is not well developed. In man hand is used for handling objects.this has been facilitated by several anatomical changes in hands.

2). thumb of man is more elongated then that of apes,though both have opposable thumb.

3). terminal phalanges in man wider;it is narrower in apes man is thus capable of precision grip to the greatest extent.

4).phalanges are curved in apes,straight in man

5).the angle between thumb and index finger is greater in man than in apes.

6).hand muscles in association with thumb. i.e. abductor pollicies and abductor pollicies are better developed in man.

Differences in skull:

1).Nuchal crest, present at the back of skull, is lesser developed in man than the apes.the crest serves to attach nuchal muscles of neck that balance the head in quadrapeds. skulls is well balanced in man hence nuchal muscles are also reduced resulting in slender neck in man.slender neck can perform maximum rotation.

2). sagittal crest is not much developed in man,whereas in apes itis developed.the crest serves to attach jaw muscles which are heavy in apes.

3).in man, cranial part of the skull is large than the facial part whereas reverse is true for apes.

4). cranial capacity of man average 1400cc whereas apes between 500-600cc. lowest in chimp and highest in gorilla.

5).in man both frontal and parietal are well archedand have tuberosities. In apes, they are not well arched and tuberosites are not well marked.

6).in man premaxilla is not well marked off from maxilla.in apes it is well marked off.

7).superorbital ridges are not much developed in man.in apes it is generally well developed and may be continuous or separated.

8). occipital region bulges out in man,in apes itis flat and receding.

9). foramen magnum is placed anteriorly at the base of the skull.in apes it is placed posteriorly towards dorsal side.

Differences in Brain:

1).association areas, the seat of memory,intelligence,reasoning learning etc constitute large areas in frontal lobe. This seat of higher intellectual faculties are particularly well developed in man.

2). greater chunk of somatosensary areas and motor areas are developed to hands,lips and mouth because the selective advantage it confers through flexible hands and vocal communication and the size of chunks increases from monkeys to apes to man.

3). visual cortex in occipital lobe morre developed and olfactory lobes less developed in man than apes.

4).nerve fibre connection between cerebellum and cortex is maximum in man hence man has maximum conscious control of coordinated muscular movement.

5).the limbic system of brain is brought more under conscious control in man because of interconnection of the system with cortex.

Cultural and other differences:

1).high intelligence and ability to concentrate has played a great role in development and culture.

2).acquisition of languages and script has led to complex social life,sophisticated art form and accelerated technical progression that has further enhanced the dichotomy between man and all animals.

3).in man lips in association with tongue palate and pharynx play a great role in vocalization hence it is well developed thicker and red.in apes, lipsare stretched over margin of jaw without medium furrow in upper lip.

4).hearing is vital for vocalization hence pinna has rolled margins in man for echo-location.

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