3 Man’s Place in Animal Kingdom

Prof. S. Jibonkumar Singh

Contents of this Unit

1. Introduction

2. Characteristics of mammals

3. Primate diversity

4. Summary

Learning outcomes:

To discuss Kingdom Animalia
To trace how Man evolved in animal kingdom
To highlight the basic features of Mammalia and its sub classes.
To study the salient features of Primates.
To portray the differences between man and other animals
To assign a systematic position of man.

INTRODUCTION:

All living organisms can be placed into one of five kingdoms: plants, animals, fungi, nucleated single celled organisms, and bacteria (Relethforth, 2010). Of all these living organisms, about 5 to 10 million species are animals and plants inhabiting on the surface of this earth today (Standford et al.2012). Texonomically animal kingdom in which man belong to can be broadly classified into 2 groups viz., i) Protozoa – Unicellular and ii) Metazoa – Multicellular. Multicellular animals though differing in form and structure have some fundamental similarities among them such as arrangement of cells, body symmetry, nature of coelom, segmentation, presence or absence of notochord etc. and man belongs to this group. On the basis of presence or absence of notochord – a flexible internal rod that runs along the back of the animal which acts to strengthen and support the body, metazoans are further divided into two Phylum – Non-Chordata or Invertebrates (notocshord absent) and Chordata (notochord present). Owing to the presence of notochord, man is placed in the later. Phylum Chordata which includes animals characterized by the presence of a notochord is further divided into three sub-phylum – Urochordata (Notochord in larva stage), Cephalochordata (Notochord extend from head to tail) and Vertebrata (notochord is replace by vertebral column). One characteristic of vertebrates is that they have bilateral symmetry, which means that the left and right sides of their bodies are approximately mirror images. Imagine a line running down a human being from the top of the head to a spot between the feet. This line divides the body into two mirror images (Relethforth, 2010). The presence of vertebral column in man justify his position in the sub-phylum vertebrata which has been further divided into five classes, viz. Pices, Amphibian, Reptilian, Aves and Mammalia. The nature of living and structure of the reproductive organs of Amphibian stand away from considering man as a member of that class. The Reptile is cold-blooded animals and that is sufficient to excluded warm-blooded man for the class Reptile. The absence of feathers would eliminate the idea of including man with the other members of the class Aves. Therefore, naturally, man belongs to the class Mammalia (Fig.1). Lets us see why man is a mammal by going through its characteristics in detail.

Figure 1. Classification of Animal Kingdom up to Mammalia Showing the Position of Man

CHARACTERISTICS OF MAMMALS

Mammals are air breathing warm-blooded vertebrates,
they have epidermal covering in the form of hair,
presence of mammae or mammary glands is the most important feature which justifies for giving the term “Mammal”,
most mammals are viviparous i.e do not lay eggs but give birth to young ones directly,
young ones are nourished from the blood system of mother through placenta before the birth and after the birth by breast milk of the mother,
presence of sweat and sebaceous glands,
presence of inter vertebral disc in the vertebral column.
scapula of pectoral girdle articulates with the sternum by means of a clavicle.
four chambered heart and lungs freely suspended within the cavity of thorax,
heterodont i.e., teeth of different types and are thecodont i.e. embedded in the sockets of jaws
The skull is dicondylic i.e., with two occipital condyles on two sides of foramen magnum in the skull,
RBCs are circular in shaped and non-nucleated,
External fertilization.

The class Mammalia (Fig. 2) is again divided into two different sub classes, namely i) Prototheria and ii) Theria. Prototheria is the egg-laying mammal, sharing much character with reptiles and birds. Though, this group of animals belon to class Mammalia, they, in fact represent a transitional stage between reptiles and mammals. Duck-billed platypus and Spiny ant-eater are the examples of Prototheria. Man does not belong to the former as the members lays eggs, hatch them out and then suckle their young ones. So, men belong to Theria which give birth to young ones and has been further divided into two section- Metatheria and Eutheria. In Metatheria, the placenta which is the characteristic of man is either underdeveloped or function for only a few days. Metatherians are those pouch equipped viviparous mammals. They are known by the term “Marsupials” The pouches on the mothers’ abdomen are meant for shelter of their young ones. Nipples are present inside the pouches for feeding their young ones. Kangaroo, teddy bear kola and American opossum belong to this section. They are known as marsupial or pouched mammal. The Eutheria or placental mammals in which men is the member consist of nine orders, namely-Edentata, Cetacea, Sirenia, Ungulata, Carnivora, Insectivora, Cheiroptera, Rhodentia and Primates. Brief characteristics of eutherian mammals are presented below.

Figure 2 Classification of Class Mammalia

Orders of Eutheria-

Cetacea: Sea dwelling mammals. Forelimbs are modified into paddle-like structures and hind limbs disappear completely. Example – Blue whale
Sirenia: They are the aquatic mammals. Herbivorous food habit in nature. Example – Dolphins
Insectivora: Mammals consuming insects as their sole food. They are usually nocturnal and smaller in size. Example – the Mole, Tree shrew, etc.
Carnivora: These are those mammals that live on the flesh. They have well developed cutting and tearing teeth and sharp claws. Example – Dog, Cat, Lion, Tiger, etc.
Ungulata: They are ground dwelling, four footed hoofed mammals usually having horns.Herbivorous food habit in nature. Example – Horse, Cow, Buffalo, etc.
Edenta: Enamel lacking mammals. Some of them are completely toothless. Example – Armadillo.
Rhodentia: Small size, furry mammals and having claws in fingers. Presence of large, chisel-like incisor teeth. Example – Rat, Rabbit, Squirrel, etc.
Cheiroptera: Flaying mammals in which four-limbs are modified into wings. Elongated bones making a broad web of skin and it extends up to hind limbs. They exhibit aerial form of life. Example – Bats
None of the above mentioned basic features of Eutheria, can’t be acceptable features of Man e.i., man doesn’t belong to those above mentioned orders. Hence, it can be stated that man should belong to the only remaining order of the placental mammal known as Primate.
Primate: Prosimii and Anthropoidea, that is Ceboidea, Crecopithecoidea and Hominoidea; including, Hylobatidae, Pongidae and Hominidae constitute the order primate. Generally, primates can be divided into broad categories: human and non-human primate.

Primates

Man, after all, is one among the 300 living species of primates and 4000 living species of mammals (Standford et al.2012). Therefore a full in depth study of the primate behaviour would include a focus on the human as well as the non-human aspects. Carolus Linnaeus was the first scientist who gave the idea that man has a common origin with the primates in his splendid work ‘Systema Naturae’in 1758. Though the term Primate mean either ‘highest’ or‘first’ and both (Eckhardt,1979) for specific order of animal kingdom containing monkeys, apes and man and it is neither the most primitive nor the most advanced of the mammalian order (Minkoff, 1983). Primate has been defined as “Unguiculate, claviculate, placental mammals, with orbits encircled by bone; three kinds of teeth, at least at one time of life; brain always with a posterior lobe and calcarine fissure; the innermost digit of at least one pair of extremities opposable; hallux with a flat nail or none; a well developed caecum; penis pendulous; testes scrotal; always two pectoral mammae (Mivart 1873)”. Almost all primates except human and a few modern primates are completely arboreal in habit, and therefore possess physical features adapted or suited to arboreal habit. Such features are even retained through inheritance among the terrestrial primates Some important and silent features of Primate are as follows-

The limbs are prehensile and adapted arboreal life. This was probably an earliest mammalian characteristic.
Either the thumb or the great toe or both are opposable there by helping in firm grasping during arboreal locomotion
All the digits of both the limbs have flat nails and sensitive touch pads with friction ridge underneath with the exception of only few primitive primates among whom either the second or third digit or both are provided with claws.
They have well developed clavicles facilitating free movement of arms in all planes during locomotion.
Unlike the mammary glands found in the abdominal region of other non primate mammals, Primates have mammary gland placed in pectoral position thus making it easy to feed young ones in face to face in position even during arboreal locomotion. .
Primates have brain with well developed posterior lobe and reduced olfactory lobe as a result of which they have highly developed binocular, stereoscopic and visual convergence and reduced snout and sense of smell. Consequently they observed the food items with their eyes and take it to the mouth i.e food goes to the mouth while for non human mammals, they smell first and eat it with mouth. The primates provide only one offspring at the time as parents unable to protect more than one at the time when they are in arboreal and danger environment.\
Nearly all primates have uterus simplex thus usually give birth to single offspring at a time and longer duration of gestation. Moreover they have longer period of parental care for young ones.
As the young one need longer parental care the time interval between successive births is longer than other non primate mammals.
The orbits are completely surrounded by bony rim so that eyes are more effectively protected than open orbits of lower mammals and forward in position for giving maximum visual convergence.
Dentition is suited to an omnivorous diet.
Longer postnatal growth. Development of sexual maturity takes longer time.
The primates possess pendulous penis.
They have well developed caecum.

PRIMATE DIVERSITY

Many Primatologist gave their own opinion as to the classification of the order Primate. But, one of the generally accepted comprehensive and traditional classification is that of Simpson (1945) (figure-1). According to him, the living primate may be conveniently classified into two orders-Prosimii and Anthropoidea.

Prosimii

The name Prosimii is derived from (pro- before; simian –ape), and German word describes them as Halbaffe which means half- ape (Weiss and Mann, 1978). Generally the Prosimii are fox-like muzzle elongated face, complete absence of postorbital wall, foramen magnum is further back compared to other primates, the thumb and toe opposable, lower extremities longer than upper extremities, almost all arboreal and nocturnal and the dental formula 2.1.3.3, etc. All these characters far removed man from this sub-order. The three infra-orders-Lemuriform (lemurs), Lorisiform (lorises) and Tarsiform (tarsiers) falls in a convenient category in former sub-order Prosimii. Further infra-order Lemuriformes is conveniently classified into two super families of Tupaioidea, and Lemuroidea. The Tupaioidea has only one family Tupiidae. Lemuroidea are classified into families Lemuridae, Indriidae and Daubentonioiidae, of which the Lemuridae are primitive in majority of the characters, while Daubentonoiidae are all together aberrant and are often regarded as an independent superfamily. The infra order Lorisiformes comprises of the single family Lorisidae. The infraoder Tarsiformes represent an important link between the two suborders Prosimii and Anthropoidea, in having many features in between the two.

Anthropoidea

In sub-order Anthropoidea includes, besides Man himself, a considerable number of more or less quadrupedal forms of generally man like body shape and head form popularly refer to as monkeys and apes. Some of the features vary from Anthropoidea are-

The lower incisors and canines do not form a tooth comb
The complete development of the post orbital wall
The strong reduction in olfactory apparatus
The short snout
The formation of nails on all fingers and toes

The conventional divisions of this suborder are Platyrrhine and Catarrhine infraorders classified based on nasal characters. In the former nostrils are round and separated by a broad nasal septum and are often refer to as broad nosed monkeys while the nostrils in the later are separated by a narrow nasal septum, comma shaped and pointing downward and often referred to as sharp nosed monkey. The infra-order Platyrrhine has one super-family-the Ceboidea with one family-Cebidae (New world monkey). The infra-order Catarrhine has two super-families-the Cercopithecoidea with one family–Cercopithecidae (Old world monkey) and the other super-family Hominoidea. As Hominoidea differ from lacking in external tail, cheek pouch and Ischial calosities, men stand apart from Ceboidea and Cercopithecoidea and belongs to Hominoidea super-family.with three families-Hylobatidae ( gibbon and siamang), Pongidae (himpanzee,gorilla and orangutan) and Hominidae (man). The name Anthropomorpha is sometimes used as a synonymous name for the superfamily Hominoidea (Montagu, 2010). The members of these families had jointly been referred to as higher primates having in common a great many important characteristics. In the absence of pre-maxilla bone, presence of chin and in many other details, man differs from the anthropoid apes and as such it could not be included under either of the two families viz. Hylobatidae and Pongidae. Thus, the position of man is found in the family Hominidae forming one genus ‘Homo’ and a single Species ‘sapien’. Man has many distinguishing characteristics by which he is separable from other members of the other families of Hominoidea super family.

Table 1. Conventional Classification of Living Primates

Though this traditional system of classification is still widely used and accepted, a modified and a more recent classification (Fig. 3) was developed by St. Hilaire in the late eighteenth century (Standford et al.2012). Following this classification, the two suborders of Primate order are Strepsirhini and Haplorhini unlike Prosimii and Anthropoidea of traditional classification. This classification is made on the basis of nasal characteristics. Members of Strepsirhini have their nasal tips provided with naked and moist skin called rhinarium, while absence of rhinarium for Haplorhini. In this scheme of classification, all the members of infra order Lemuriformes and Lorisiformes of traditional classifications are kept under Strepsirhini suborder while all the members of infra order Tarsiformes and suborder Anthropoidea of taditional classification are kept under Haplorhini suborder.

Whatever the classification of Primates be, Man is placed in the super family Hominoidea along with the lesser and great apes. The following classification (Fig. 4) of this super family can clearly illustrate man’s taxonomic place therein.

Super Family Hominoidea

The super family Hominoidea consists of three families: Hylobatidae, Pongidae and Hominidae. Hylobatidae (Gibbon) and Pongidae (Orangutan, Chimpanzee and Gorilla) are commonly known as Apes (Fig.4)

Fig.4. Traditional taxonomic classification of Hominoids. Names in italics refer to common names (Source: Relethforth, 2010)

Following this scheme of classification, the lesser apes i.e. gibbons, siamang are placed in the family Hylobatidae. Hylobates differ from great apes (chimpanzees, gorillas, orangutans, bonobos and humans) in being smaller, exhibiting low sexual dimorphism, in not making nests, and superficially more closely resemble monkeys than great apes. Gibbons brachiate, up to 15 m (50 ft), at speeds as high as 55 km/h (34 mph). (http://www.nhptv.org/wild/hylobatidae.asp)

The family Pongidae comprises three genera namely, Pongo, (orangutan) Pan (chimpanzee) and Gorilla (gorilla). Orangutans live on vegetarian diet and very fond of fruits. Males are much larger than females (sexual dimorphism). They sleep in the nest built by them. Cranial capacity ranges from 365 cc to 425 cc ( https://en.wikipedia.org/wiki/Orangutan ). Height of gorilla ranges from 5 to 6 feet and body weight varies from 200 to 250 kg. Cranial capacity ranges from 450 cc (females) to 500 cc (males). They spent most of their time on the grounds, but can climb on the trees. Nests are built on the trees to pass the nights there. They walk quadrupedally and sometimes bipedally (Roy, 2012). Chimpanzee vary considerably in size and appearance, but chimpanzees stand approximately 1–1.7 metres (3–5.5 feet) tall when erect and weigh about 32–60 kg (70–130 pounds). Males tend to be larger and more robust than females. Cranial capacity ranges between 400 cc to 500 cc (Roy, 2012).

Man certainly differs from gibbons, orangutan, gorilla and chimpanzee in a number of above characteristics, thus placing him in a separate family having the following features.

Bipedalism (orthograde) mode of locomotion with erect posture (autograde),
Communicate each other through articulated speech,
Slow and gradual rate of growth and development with prolonged growth period,
Longer life span as compared with those of other primates,
Upper extremities are much shorter than lower extremities,
Absence of ischial callosities,
Relatively hairless body except dense hair on scalp and certain specific areas of the body,
Highly rolled margins of ear,
Prominent nose with elevated bridge and fleshy tip,
Enlarged cranium and reduced facial portion,
Cranial capacity ranges from 1300 cc to 1450 cc approximately,
Placement of foramen magnum far anteriorly at the base of the skull for balancing the head on the vertebral column,
Development of pyramidal mastoid process and styloid process,
Presence of well-marked linea aspera in femur bone,
Absence of diastem, smaller canines and reduced size of molar teeth.

These special features have given the man at top place in the animal kingdom. Therefore, position of man among the mammals can be traced in the following heirarchial position:

Kingdom –Animalia

Phylum- Chordata

Sub-Phylum- Vertebrata

Class-Mammalia

Sub-Class- Eutheria

Order- Primate

Sub-Order-Haploirini

Infra-Order- Catarrhine

Super –Family –Hominoidea

Family- Hominidae

Genus- Homo

Species- sapiens

Sub Species– sapiens

SUMMARY

- Classification of Animal Kingdom is based on some fundamental features like level of organisation, symmetry, coelom, segmentation, presence or absence of notochord etc. Of these features, presence of notochord and backbone justifies man’s inclusion in the phylum Chordata and sub-phylum Vertebrata respectively.
- Out of the five taxanomic classes of sub-phylum Vertebrata viz. Pices, Amphibian, Reptilian, Aves and Mammalia, man is placed in the last class i.e Mammalia mainly because of presence of Mammary glands and viciparous nature i.e giving birth to young ones directly instead of laying eggs.
- Of the nine eutherian mammalian orders, namely-Edentata, Cetacea, Sirenia, Ungulata, Carnivora, Insectivora, Cheiroptera, Rhodentia and Primates man belongs to the Order Primate as they possess prehensile limbs, opposable great toes and/or thumb, flat nails, well developed clavicle, vision with stereoscopic, binocular and visual convergence, pectoral mammae etc.
- Among the primates, man is placed in the sub-order Anthropoidea jn conventional classification and Haplorhini in more recent one owing to the presence of non procumbent incisors and canines, complete development of the post orbital wall, strong reduction in olfactory apparatus, short snout with no rhinarium, formation of nails on all fingers and toes etc.
- Owing to the presence of nostrils separated by a narrow nasal septum, downward pointing nasal nostrils and will elevated nasal bridge; man is placed in the infra-order Catarrhini of sub-order Haplorhini,
- In the infra-order Catarrhini, man is placed in super-family Hominoidea because of absence of tail, laterally expanded chest, very large complex brain, arms longer than legs (except man), more or less semi erect or erect posture etc.
- Finally man is placed in species sapiens, genus Homo of family Hominidae characterized by orthograde posture, highly complex brain, very less body hair, prominent nose with elevated bridge and fleshy tip, enlarged cranium and reduced facial portion, articulated speech etc.

you can view video on Man’s Place in Animal Kingdom

References

Das, B.M. 2008. Outline of Physical Anthropology. 26th Edition,KitabMahal ,Allahbad Echhardt, Robert.B.1979, The Study of Human Evolution, Mc Graw. Hill Companies, New York. Minkoff, Eli. C. 1983. Evolutionary Biology. Addison Wesley Publication Company, USA.
Mivart, St George Jackson. 1873. Man and Apes. Popular Science review, A quarterly miscellany of entertaining and instructive articles on scientific subjects, London.
Montagu, M.F. Ashley. 2010. An Introduction to Physical Anthropology. Third Edition , First Indian Reprint, Surjit Publications, New Delhi.
Park, Micheal. Alan.2005. Biological Anthropology: An Introductory Reader. 4th Edition. Mc Graw. Hill Companies, New York.
Relethford, John. H. 2010. The Human Species: An introduction to Biological Anthropology. 8thEdition.
McGraw-Hill Companies, Inc. Americas, New York.
Roy, Indrani Basu. 2012. Anthropology: The study of Man. S. Chand and Company Ltd., New Delhi
Simpson, G.G. 1945. The Principles of classifications and a classification of mammals, Bull.Am.Musium Natur, Hist 85; xvi-350
Weiss, Mark. L and Alan E. Mann. 1978. Human Biology and Behaviour: An Anthropological Perspective. Second Edition Little Brown and Company Ltd. Canada
http://www.nhptv.org/wild/hylobatidae.asp. Retrieved on 20th May 2015, 14.00 hrs https://en.wikipedia.org/wiki/Orangutan. Retrieved on 20 th May 2015, 14.20 hrs

Reading list

Hooton, A.E., Up from Ape, Macmillan, Delhi, 1965
Le Gros Clark, W. E., History of Primates, Natural History Museum, London, 1949
Simpson, G.G., Principles of Animal Taxonomy, Columbia Univ. Press, Newyork, 1961.