Man, the unique product of evolution shares many features with other animals. The basic biological reality of man can be understood by assessing the nature and extent of his various biological features. An insight into the features reveals man’s position in animal kingdom.
The following chart shows man’s position in animal kingdom:
Animal Kingdom is divided into two sub-kinadoms: a) Protozoa, b) Metazoa. Protozoans are unicellular organisms but metazoans are multi cellular organisms. Humans come under metazoa because their body contains numerous cells. Metazoa are divided into 2 phyla: a) Non-chordata; and b) Chordata. Humans belong to chordata because a flexible internal rod runs along their back. In humans, it is present early in gestation and is later reabsorbed. Thus, humans are different from non-chordata.
Humans also belong to the sub-phylum Vertebrata because; the internal spinal cord is covered by an articulated series of bones known as Vertebrae. Thus, the presence of Vertebral column would justify the position of humans among the Vertebrates. The sub-phylum of vertebrata includes several classes, namely Pisces, amphibians, anes, reptiles and mammals.
Humans belong to the class of mammals because they share the following characteristics of mammals:
- I) Mammals are air-breathing animals.
- ii) They have epidermal covering in the form of hair.
- iii) They are warm-blooded.
- iv) They are- viviparous.
- v) The fetus is nourished before birth from the blood system of mother through placenta. They have mammary glands. After birth, the infant is nourished by breast milk of the mother.
- vii) Teeth are different in shape.
- viii) The heart is completely four-chambered organ. It is divided into two halves; each consisting of an auricle and a ventricle.
- ix) The body cavity is divided into two (thorax, abdomen) by a diaphragm.
- x) The uretra made from the kidneys to the urinary bladder.
Man is not merely a mammal but a different kind of mammal. The class mammalia has two subdivisions: i) Prototheria and ii) Theria. Of these two, man does not belong to Prototheria, as they lay eggs and hatch them out. But, man belongs to ‘Theria’ as he begets the young.
Again, the sub-class ‘Theria’ has two sub-divisions namely, (i) Metatheria and (ii) Eutheria. The metatheria animals develop the young outside the womb but the eutherians develop the young inside the womb. Therefore, man belongs to eutheria.
Eutheria includes two infraclasses: (i) Placental; and (ii) Non-placentals. Man is a member of the Placentals. The Placentals consist of nine orders, viz.,:
- 1) Edentata (anteaters, sloths, armadillos).
- 2) Catalea (whales).
- 3) Sirenia (porpoise like animals).
- 4) Ungulata (cattle, deer and other hoofed animals)
- 5) Carnivora (cats, dogs, tigers, etc.)
- 6) Insectivora (Shrews and roetes).
- 7) Cheiropetra (Bats)
- 8) Rodentia (Squirrels, rats, rabbits).
- 9) Primates (man, apes and monkeys)
Humans belong to the order Primates because of the following characters:
- Primates have prehensile limbs adapted for arboreal life.
- Either the thumb or the great toe or both are opposable.
- They bear flat nails upon their digits. This makes the grasping function of hands and feet easier.
- They have a well developed clavicle.
- The orbits are completely surrounded by bony rims.
- Atleast three kinds of teeth are present at one time of their life incisors, cannines and premolars to serve different functions.
- There are two pectoral mamma.
- The brain always has a calcarean fissure and a posterior lobe.
- The testes are descended into the scrotum.
- There is pendulous penis.
- The canum is well developed.
- The stomach is simple
- The femur never has a third tro-chanter.
Within the Primate order, man occupies a supreme position. The primate order includes two sub-orders:
- (i) Prosimii
- (ii) Anthropoidea.
ProSimii are of lower order primates. The Prosimian sub-order includes four infra orders:
- (i) Tupaioidea (tree shrews).
- (ii) Torsioidea (Malayan and Philippine Torsiera)
- (iii) Lorisoidea (African and Asiatic Lemurs).
- (iv) Lemuroidea (Madagascar Lemurs).
Anthropoidea is divided into two infra orders:
- a) Platyrrhine (New World Monkeys)
- b) Catarrhine (Old World Primates)
The Platyrrhine are called as such because of their flat nose but the catarrhine’s have a downward positive nose. The Catarrhines includes old world monkeys,apes and humans because they have a downward pointing nose.
Catarrhine comprises of two super families:
- (i) Cercopithecoidea (old world monkeys).
- (ii) Hominoidea (Apes and man):
The Cercopithecoidea is called as such because of the prehensive tails. For this reason, old world monkeys come under this category. On the other hand, hominoidea do not have tails. As such apes and humans appear under this category. Homrnoidea is divided into three families:
- (i) Hylobatidae (Gibbons and Simangs).
- (ii) Pongidae (Orangutan, Gorilla, Chimpanzee).
- (iii) Hominidae (Man).
Humans have pre-Maxilla bone, but have chin and in many other details they differ from Hylobatidae and Pongidae. As such they cannot be included under either of these families. Therefore, humans constitute a separate family Hominidae.
The family Hominidae has the following characters:
- (i) Bipedal walk.
- (ii) Fully erect posture.
- (iii) Large complex brain.
- (iv) Reduction in the density of hair except on scalp.
- ( v) Legs longer than the arms.
Hominidae includes two genera:
- (a) Australopithecus
- (b) Homo.
Australopithecus became extinct almost as half million years ago giving rise to the groups Homo. Among the Homo, the first belongs to the species, “habilis”, next to “erectus” and the later one “Sapiens”. Afterwards, “Sapiens” themselves evolved into the varieties or sub-species namely “neandertalensis” and Sapiens”. Modern man is Homo Sapiens Sapiens.
The present description makes an attempt to reach out the position of man in the animal kingdom. In this context it focuses on the specific characteristics, which differentiate man from other animals. Man is a member of the Primate order. It is certain that man presents the required primate characteristics in his body for his inclusion in that order but what is important is that man has developed a number of specific characters, which have given him a unique position in the whole of the animal kingdom.