Essays on Man - by Students of Biology

K.K. Verma and Rashmi Saxena

Copyright 1998Eubios Ethics Institute 1998. All commercial rights reserved. This publication may be reproduced for limited educational or academic use, however please enquire with the author. A printed version may become availbale in the future. NOTE the views of this book are not necessarily those of Eubios Ethics Institute, which promotes intellectual debate, but the views of the authors.

About the Authors

Dr. K.K. Verma is Retired Professor of Zoology and Principal, Government P.G. Colleges. Did his M.Sc. in Zoology with specialisation in Entomology from the Saugar University, Sagar (India) in 1956. Soon afterwards he started his career as a teacher in Zoology in the M.P. Government, Department of Higher Education. Having taught his subject both at undergraduate as well as postgraduate levels as Lecturer, Assistant Professor and then as Professor in different M.P. Govt. Colleges, he was promoted as Principal in 1983, from which position he retired in 1991.
Dr. Verma's research area has been "Insect Functional and Comparative Morphology". He was awarded Ph.D. by the Ravishankar University, Raipur (India) in 1967. He has to his credit more than 25 research papers published in national and international journals. He participated in the International Congress of Entomology at Hamburg in 1984 and at Vancouver in 1988.
After retirement he has developed interest in Bioethics, and has taken to popular scientific writing.

Dr. Rashmi Saxena is a daughter and an intellectual companion of Dr. K.K. Verma. She did her M.Sc. in Zoology with Entomology as the special branch from the Ravishankar University, Raipur in 1985. After teaching her subject as Lecturer in M.P. Government colleges for a few years, she gave up the job to join as Research Associate for a UGC sponsored research project. On completion of the project in 1997 she again took to college teaching in Udaipur (Rajsthan).
Dr. Saxena's area of research has been biocontrol of insect pests of stored grains. She was awarded Ph.D. in 1989 by the Ravishankar University, Raipur. She has authored half a dozen published research papers.

INTRODUCTION

The nine essays, included in this collection, have been written with a firm conviction that understanding Man* with his biological background helps in knowing him better. This approach enlightens us as to significance of Man in the living world, what he can do or overdo, and what errors he should avoid hereafter. Man has a lot of misconceptions about his own affairs, and the misunderstandings can be got rid of through biological understanding of him-self.

As has been vividly brought out by Crow (1970), Modern Man's view of himself has developed with growth of evolutionary biology and with understanding of mechanism of inheritance. Various other branches of Biology, such as Comparative Anatomy, Comparative Physiology, Biochemistry, Cell Biology and Ecology, have all contributed to the development of the views.

Efforts to understand Man have been made by several eminent biologists, Julian Huxley, Theodor Dobzhansky, J. B. S. Haldane and N. J. Berrill to name some. The essays, presented here are mostly an assimilation of the thoughts of these scientists, along with some sprinkling of our own interpretations.

Presentation of matter is almost nontechnical, so as to make it accessible even to readers with little familiarity with biological sciences.

* The term "Man" is used throughout this book as a synonym for human beings. It has no intention to be sexist in expression, including equally both male and female of humankind.

1.UNIQUENESS OF MAN

Introduction

Man has always realized that he is a part of the living world. According to the ancient Vedantic philosophy "atman" or the life force moves from one "yoni" or level of organization to another. In stories of "Panchtantra" and Aesop's Fables human qualities were attributed to animals.

In the Middle Ages, when religion dominated Man's thinking, he regarded him-self as a superior being, far superior to other living forms. Gods were humanised. In the Christian scripture it was said that God had created Man out of his own image.

At about the middle of the last century an important event took place in the scientific world; Charles Darwin, in his book "Origin of Species" (1859) offered us the concept of organic evolution as a scientific theory. According to this theory living forms are not static; they change with the passage of time in order to become better adapted to the existing conditions. When this happens in populations of the same species, living in different areas with somewhat different conditions, this may lead to the populations becoming, in due course, different and new species. Similar views had been expressed by some biologists and thinkers before Darwin, but Darwin was the first to put forth these views adequately supported by a large mass of evidence.

Publication of Darwin's "Origin of Species" has been described as the most important event and a turning point in the history of Biology. The concept of evolution became generally accepted among people of science, following publication of the book, and in the next few years the entire science of biology underwent a rapid remoulding on the basic theme of organic evolution.

Charles Darwin wrote also a small book, "Descent of Man", which was published 12 years after the appearance of "Origin of Species". In this book the author described that, like other organisms, Man had been a product of evolution, and that he had descended from some primitive tree living apes, his closest living relative being the chimpanzee. Similar views had been presented by a strong supporter of Charless Darwin, Thomas Huxley in 1863 in his book, "Evidences as to Man's Place in Nature". With these publications Man came to be regarded as another product of evolution, as another animal species. Thus Man's opinion about his position in nature underwent a drastic change, from that of a very superior being, next to God in position to that of just another member of the Animal Kingdom.

The present century has witnessed a rapid progress in our understanding the mechanism of inheritance among organisms. Thus the branch of Biology, called Genetics, has developed fast. Growth of Genetics has helped a better understanding of the mechanism of evolution, as evolution is only descent with modification. This situation plus continued pondering among biologists on how Man differs from the remaining animal species has led to the realization that, while Man represents culmination of an evolutionary line among the mammalian order Primates, he has come to acquire during his evolution such unique features as make him stand quite apart from the rest of the Animal Kingdom. He is obviously the dominant living being on the planet at present. His dominance, as we shall realize it in course of these essays, is quite different from and much more pronounced than the dominance of dinosaurs in the Mesozoic Era (i.e. the period of reptiles, which ended about 70 million years ago, and the duration of which is estimated to have been nearly 140 million years), or that of mammals in the early part of the Caenozoic Era (i.e. the current geological era, which started about 70 million years ago).

Man, a product of evolution

That Man is a product of evolution among animals and that he is a member of the Animal Kingdom cannot be doubted. Testing newly discovered drugs and pharmaceuticals on rats, guinea pigs and monkeys is done with the realization that Man has the same basic physiology as these animals. There is considerable fossil record to support the notion that Man has evolved from primitive ape-like ancestors, and that the living chimpanzee is the closest living relative of Man. In serological test anti-human sera are almost as strongly positive with chimpanzee blood as with human blood, supporting the above pointed notion of evolutionary closeness between them. It may be noted further that reaction of the antihuman serum is weaker with blood of other apes, still weaker with blood of monkeys and baboons, which are more distantly related to humans than apes, and almost imperceptible with blood of lemurs, which are the most primitive members of the group Primates, and which are thus farthest separated from humans in phylogeny.

Now let us consider some probable unique attributes of Man.

Human intelligence and speech

One of the peculiar features of Man is his greatly developed intelligence, which has largely replaced his instincts. How do instincts differ from intelligence? A long answer is needed to satisfy this question; hence a separate essay on this problem, see Essay 2.

Perhaps the most acceptable definition of intelligence is that it is the capacity to modify one's behaviour according to the needs of the moment on the basis of learning through past experience. One special feature of human intelligence is symbol formation or symbolization or conceptual thinking. For each experience we mentally form a symbol, which may be expressed orally by speaking out a word or a set of words or by writing. Man can express a series of such symbols or words in an articulate manner, and thus have developed speech, language and writing, which have played such a vital role in the development of human social pattern.

While speech and language have been outcome of symbolization or concept formation, it is also true that they have helped concept development. As Julian Huxley (1959) has put it, words are tools which automatically carve concepts out of experience. More about it in the next essay.

Intelligence and concept formation did not appear all of a sudden at the human level during primate evolution. Though in a rudimentary form, these attributes may be seen among apes. At Stanford University and the University of Nevada, chimpanzees and gorillas have been taught to communicate by using the American Sign Language (=Ameslan). (It may be pointed out at this stage that in the great apes the vocal cords are such that they are unable to produce a variety of sounds; hence use of intricate oral symbols or words for expression is difficult in their case.) At Georgia State University the apes have been taught to use a modified computer key board. Such experiments have shown that the apes are fairly capable of associating experiences with certain symbols, and they too are capable of fair amount of articulation.

Even in the wild the apes seem to have some capacity of communication. This may be inferred, for example from an experience narrated by Jane Goodall. In East Africa two young gorillas had been shot dead by someone from a jeep. The gorilla tribe, which had thus lost its two members, avoided jeeps and cars for years after the event. This could not have happened in the absence of some communication among members of the tribe.

Prehensile or object-holding hands

There are reasons to believe that the ancestor of Man was an arboreal creature with the habit of brachiating, that is swinging, with the help of prehensile or object-holding hands, from one tree branch to another, like the present day apes. Thus Man's prehensile hands, with the thumb foldable against the palm, have been a legacy from a tree living ancestor. Not only the prehensile nature of the fore-limbs but also extra sensitive palms have been a part of this legacy.

When the evolving Man left life on trees and started moving on land, he took to bipedalism. His hands, now freed from locomotion, could be used for holding various external objects, and using them as such or with some modifications, in order to increase his mechanical efficiency. Human intelligence prompted this use of hands to make extensive and intricate modifications in such objects. Thus started making and wielding of tools, weapons and implements, or in brief, technology, which is an important characteristic of Man.

Like intelligence and conceptual thinking, use of tools did not appear de novo in human evolution. Rudiments of tools using behaviour may be seen in some animals. A wasp, Ammophila makes its nest in the form of a blindly ending tunnel in the ground. This she does by digging with aid of her jaws and spiny fore-legs. After laying her egg in the nest and placing some food for the future larva, the mother wasp puts a small pebble on the funnel-like mouth of the tunnel, and then places the earlier dug out loose earth over the mouth. Now, in order to camouflage the spot and protect it from parasitic and predator insects, she searches out a suitable pebble, which she selects after weighing several pebbles between her jaws and rejecting them. Holding the finally selected pebble between her mandibles she allows it to fall down repeatedly on the loose earth at the mouth of the nest to smoothen it. Thus the carefully selected pebble is used by the wasp as a tool.

When young Charles Darwin visited the Galapagos Archipelago as a part of a scientific expedition, he observed that a small bird, a finch had wood pecker like habit of dislodging insects, living beneath bark, and feeding on them. For this purpose a wood pecker uses its long bill, which is inserted into cracks and gaps in bark. The Galapagos finch does not have a long bill, and makes up the deficiency by holding a twig in its beak and using it as a tool for exploring the underneath of bark.

Gavin R. Hunt, a biologist from New Zealand, has recently observed in the New Caledonia group of islands in the South Pacific that a crow (Corvus moneduloides) makes and uses tools of two different types. One variety is a hooked stick. This it makes by pulling away a twig by its beak, making a nick near one end of the stick, so that the end becomes hooked. The hooked stick is used for pulling out insects from holes. A tool of a different kind is prepared by making, with its beak, successively deeper bites along an edge of a long leaf, starting near the leaf apex and proceeding towards its base. The leaf, made serrated this way, is also used for exploring holes for insect food.

Chimpanzees in the wild are also known to use simple tools. It has been observed crushing together several dry leaves to make a sort of a sponge, and using it for lifting water to its mouth, if the stream bank is too high to allow lowering of mouth to the water surface. It has also been seen to break away a tree branch, removing leaves from it to make a stick, and to use the stick for beating its chest in order to frighten and drive away an approaching enemy.

Man, with his complex tools and equipment, represents a much higher level of technological evolution. The prehensile hands of Man have made possible not only to use tools and technology, but also the capacity to make symbols on flat surfaces. Thus his object holding hands, intelligence and conceptual thinking have led to writing and literature.

Dolphins among Mammals are markedly intelligent. It has been said that, if they had prehensile limbs, they could have built their own civilization with physical signs upon the Earth like Man.

Cumulative tradition or social memory

A peculiar feature of human social organisation is that all that has been experienced or learnt so far by the present generation and all the earlier generations is passed on to the next generation. Thus knowledge and skill, acquired, go on accumulating generation after generation. This is called the cumulative tradition or social memory, as the society as a whole remembers/retains all the past experience and learning. Rich communication, through speech, writing and literature, plays a vital role in building up social memory.

Foetalization or paedogenesis and slowing of development

By paedogenesis, in human context, is meant foetal features continuing into the adult stage. Delay in hardening of the inner parts of the nasal bones, the rounded form of the fore-head, distribution of body hair in adult humans etc. make us resemble a late foetus of chimpanzee. It is believed that paedogenesis has been a factor in human evolution. Paedogenesis seems to have been accompanied by slowing of development in the evolutionary process leading to Man. The time that elapses between birth and the time of attainment of sexual maturity in Man is about a quarter of the average human life span, whereas in other mammals the corresponding period is eighth, tenth or twelfth of the average longevity. According to Bates (1963), "The human infant is completely dependent from 6 to 8 years, the ape infant for perhaps two years, most monkeys for 1 year ..... Man reaches puberty at about 14 years and full adult powers at about 20; the corresponding figures for great apes are about 8 to 12. Mammals other than Primates generally show even more rapid developmental rates."

Slowing of development and paedogenesis have resulted in a longer post-natal association between the child and the parents. This situation is helpful in construction of social memory.

Long post-reproductive phase

A long post-reproductive phase is yet another human peculiarity. In most mammals individuals generally die soon after the reproductive phase is over. In chimpanzee reproduction stops in a female at about the age of 35 years, and death occurs at about 40 years. In man, however the post-reproductive phase is long; it is as long as or longer than the reproductive phase. Moreover people in the post-reproductive period generally occupy important position in the society. Most leaders, eminent doctors, lawyers and scientists are in their post-reproductive phase of life. In fact the presence of such experienced persons amongst us is conducive to development of social memory. Sometimes our society is criticised for being gerantophilic, and critics point out that one is "too old at 40 or 45 ". But such slogans tend to rob the human society of one of its advantages.

Reticulate evolution

Man has been evolving without breaking up into species. This situation has been discussed at some length in Essay 9. Two populations, living in two different parts, evolve separately, may become different in their features, and may also become different species, if they remain separated long enough. But, because of Man's restless and migratory habits, human populations frequently undergo genetic intermixing. Thus these populations do not remain separated long enough to become incapable of interbreeding and to become distinct species. This sort of evolution, in which geographic isolates frequently genetically intermix, has been called reticulate evolution. On the other hand speciation or new species formation has been called divergent evolution.

Reticulate evolution is one of the characteristics of Man.

As has been pointed out above, reticulate evolution results from frequent racial intermixing. In Mexico 60% of 33 million population are a result of hybridisation between Europeans and Red Indians. In Colombia this is true for 40% of 11 million population. In the Urals most people are hybrids between Europeoids and Mongoloids. In fact it is estimated that half of humankind today is made up of people, who represent racial intermixing not far back in the past.

A consequence of reticulate evolution: members of different human races successfuly interbreed. In this context Bates (1963) has said, "There is ample evidence that the most different looking individuals from the most remotely separated parts of the world can interbreed if given the opportunity. Norwegians, Australian aborigines, Bushmen, Malays and South American Indians are all perfectly capable of interbreeding and producing healthy and completely fertile off-spring."

Another consequence of this situation : that the human species presents a great genetic diversity. Humans are the most genetically variable of all animal species with the exception of domestic animals. The great variability helps the fine distribution of labour in the human social structure.

The genetic variability in humans has helped invading and living in widely different habitats. No other animal species is known to occupy such very different habitats. Of course ants are also known to live in very different parts. They are met with in tropical forests, deserts, at considerable heights on mountains, along the sea shore etc.. But then there are numerous species of ants, whereas Man, a single species, occupies such a wide range of ecological conditions. Human technology has also helped us living in and adapting to different living situations.

Civilization

The different characteristics of humans, enumerated above, interact in various ways, as illustrated in the figure 1.1. The great amalgam or complex of speech and language, writing and literature, social memory (through informal and formal education), technology, fine distribution of labour and great capacity to adapt to diverse conditions and habitats, is called civilization, which in the Animal Kingdom is seen only in the human species. In this description of civilization one important ingredient is left out, human esthetic sense and the fine arts, which seem to be a culmination of our conceptual thinking.

FIG. 1.1: Interaction among different special attributes of Man.

2. INTELLIGENCE VERSUS INSTINCT

Introduction

One of the unique features of Man is his well developed intelligence. Mammals are intelligent, and Man is much more so. By such a statement we mean that mammals, and to a greater extent Man, are guided in their behaviour by intelligence rather than by their instinct, while animals at lower rungs of evolution show mostly instinctive behaviour.

What is intelligence, and how does it differ from instinct? It is not easy to come to satisfactory definitions of these two terms. As intelligence has been the very basis of human cultural evolution, let us devote some efforts to come to acceptable definitions.

Search for definitions

Commonly by intelligence we mean learning capacity and capacity to modify one's behaviour as per needs of the moment. By instinctive or innate behaviour is commonly meant inborn behaviour, for which no learning is needed, and which is not modifiable in view of immediate environmental needs. Obviously an important difference between innate/instinctive and intelligent behaviour may be that, while the former is guided more by the genotype or the gene set, the latter is more shaped by the immediate environment.

Let us see a few examples of innate behaviour in order to appreciate how much of our own behaviour differs from it.

One example we choose from Linda Partridge (1983). She points out that the garter snake (Thamnophis elegans) feeds mostly on slugs in coastal regions of California, while in inland California the same species feeds mainly on frogs and fish. This difference in food preference is not due to learning. Most freshly born coastal garter snakes attack slugs on the first exposure, while most new born inland snakes will not feed on slugs, and will starve to death, if an alternative food is not made available to them. In this snake species there is ovo-viviparity, that is eggs are retained in the genital tract of the mother, they develop there and then young snakes are born. But maternal effect during development may be ruled out, as it has been found that the progeny, resulting from a mating between an inland and a coastal snake, do not particularly resemble the mother in their food preference. These observations clearly suggest that the garter snake in different geographical areas have evolved differently through selection with regards their food preferences, depending upon the nature of food available readily. In support of this notion is the observation that, while in the coastal populations there are some individuals which do not prefer slugs, some in an inland population may almost as readily attack slugs as most individuals of a coastal population.

Another example from the work of Gwinner and Wiltschko on the European Garden Warbler (Sylvia borin), as cited by Bateson (1983). When these birds are reared in cages since hatching, they show restlessness in migratory periods, in autumn and spring. These birds in captivity and isolated from fellow individuals however, tend to fly southward in autumn and northward in spring, like their wild counterparts.

Still another example: a female mantid, reared in isolation, when sexually matured and mated, makes an ootheca, characteristic of the species, though she has not seen her mother or any other female doing so.

Compare these instances with our behaviour. Though we are not free from instinct, much of our behaviour is deliberate, modifiable in view of immediate environmental needs, and based on learning or experience.

But the definitions of instinct and intelligent behaviour, given above, are not satisfying, when we consider the following. That learning has no place in development of instinctive behaviour is not quite correct. An example to bring home this point is in Hailman's study, as cited by Bateson (1983), who says, "It is possible to take a recently hatched laughing gull (Larus atricilla) chick and show that it will peck at models of adults's bill. Advocates of the first view (that innate behaviour is entirely inborn with no place for learning) would almost certainly want to call the behaviour innate, since the chick had previously been isolated from 'relevant' experience. Nevertheless, as the chick profits from its experience after hatching, the accuracy of its pecking improves, and the kinds of bill-like objects it will peck at are increasingly restricted."

Another example: Marler (1976) has noted that in three different birds, Song Sparrow, White-crowned Sparrow and Oregon Junco, song patterns of wild and socially isolated captive males, as seen in recorded oscillograms, are obviously different.

That intelligent behaviour is environment based, but it also requires a genetic basis, is not difficult to accept. Mongolism or Down's Syndrome is due to a genetic abnormality, and the learning ability of the sufferer is greatly impaired. Identical or monozygotic twins have similar genetic base, and show very similar learning ability, while dissimilar or dizygotic twins may differ more widely in this ability.

Keeping in view all this let us continue our quest for satisfactory definitions of intelligence and instinct. According to Lorenz (1965) behaviour, based on immediate environmental information or need and previous learning, is learnt/intelligent/acquired behaviour. On the other hand behaviour, which has evolved as an adaptation to a particular set of environmental conditions, and, therefore develops under influence of the genetic mechanism, and is not pliable under influence of immediate environmental changes is innate/instinctive behaviour. While these definitions are clear and in good agreement with the common notion among biologists, the main drawback with them is that there is no room for learning modifying instinctive behaviour.

Another significant view in this context is that of Schneirla (1966) and Lehrman (1970). According to these authors a developing individual is continuously influenced by both the genes present in its cells as well as by the environment. Thus behaviour also develops under influence of the both. However, this view is too broad based to help distinguishing between intelligence and instinct.

Alcock (1979) gave a theory suggesting varying extent of influence of genes and environment in determining behaviour. Taking a cue from Alcock's views, suggestions are being made here to help formulate acceptable definitions of intelligent and instinctive behaviour. The suggestions are illustrated in the figure 2.1. As shown in this figure all behaviour is influenced both by the genetic make up of individual as well as by the environment. If in shaping of a particular instance of behaviour the current environmental information/needs and learning play a large and conspicuous role, while the role of genotype is, relatively speaking, not so well pronounced, the behaviour is called learnt/acquired/intelligent. On the other hand, if the genetic control of behaviour is well pronounced or conspicuous, and the ambient environmental conditions and recent experiences and learning play only a small role in shaping behaviour, it is innate/instinctive behaviour.

It should, however be remembered that the genotype, guiding behaviour, has evolved under influence of environment. Thus behaviour in all cases is an adaptation to the environment, though the influence of the current environmental conditions is obvious and pronounced in intelligent behaviour. But in view of all this one should not underestimate the role of the genetic mechanism, which in all cases provides the back-bone of behaviour. If the genic set or genome has evolved to such an extent that it influences development of an organism, capable of perceiving the ambient environmental features, assessing them immediately and preparing strategies for suitable response, on the basis of previous experiences/learning stored in the memory, we call the possessor of the genome intelligent.

FIG. 2.1: Diagramatic representation of present authors' views on Intelligence and Instinct. (N.B. : Thickness of straight arrows is meant to convey extent of influence. Thick arrows denote conspicuous and well pronounced influence, and thin arrows influence not so obvious.)

An alternative explanation of instinct

Psychologists have now discarded use of the term instinct. They believe that the term "has ceased to be a useful concept" (Hinde, 1974). The main objection to the instinct concept - it does not adequately explain the nature of what is called instinctive behaviour. According to Hinde (1974) to state that a certain behaviour is instinctive is to provide a cloak for our ignorance.An alternative explanation is being offered now for instinctive behaviour. This explanation, as discussed by Hinde (1974), includes two main points, viz.:

1. The so called instinctive behaviour is shown only when some internal changes, depending upon stage of development or physiological state, have taken place in the animal. Such changes produce a certain "motivation" or "urge". Perception of some external changes may trigger expression of the urge. For example, an adult in breeding season has mature gonads and the hormonal make up needed for its nesting behaviour. Certain climatic changes, ushering in the breeding season, trigger the nesting behaviour.

2. Generally what we call an instinctive behaviour includes a chain of activities, and for each activity a separate "motivation" or "urge" is needed. For example, a bird in the breeding season feels an urge to collect nesting material, then transfers the material to a suitable nesting site, and then makes or weaves a nest. As per the explanation, offered by the author, development of a motivation leads to the first or initial activity. The result of the first activity becomes the stimulus situation for expression of another motivation, resulting in production of stimulus for still another motivation and so on.

The motivation concept is no doubt a more detailed explanation of instinctive behaviour, but, even when we use this concept, we are still using a garb or a cloak to a cover our ignorance. How otherwise do we explain in the example, cited above, why a certain bird, in the initial activity of its nesting behaviour, chooses pieces of straw and not pebbles?

In our opinion "instinct" continues to be a useful term for most biological writing, though one should be aware that often when we refer to an instinct, it may be a cluster of instincts or motivational urges.

Special features of human intelligence

Mammals, specially higher primates including humans, are markedly intelligent in their behaviour. They learn by those very basic learning methods which psychologists talk of, viz. habituation, imprinting, sensitization and classical and instrumental conditioning. But these animals have some special attributes to make their learning process and intelligence remarkable and complex. The following is an attempt to make out those special features.

1. Learning facility

Birds and mammals show a well marked facility in learning. They learn faster than lower animals. Mammals are superior to birds in this respect.

2. Capacity to reorganize elements of experience and to form principles on basis of learning.

Mammals, specially nonhuman primates and Man, have the capacity to reorganize elements of past experience to solve a new problem. Let us take a simple example. The following experiment is included in the text-book by Dethier and Stellar (1968). Some rats were taught two different activities separately. Activity number 1 : the rats learnt to use a ladder to climb down from a table to the floor and explore that floor for food. Activity number 2: they were later taught to climb up a ladder to reach a table top, from which they used a run-way or bridge to reach another table top with food. After the rats had learnt well the two activities, a special situation was created. Two tables with ladders were arranged in a room. On table number 1 some food was kept, but it was so fenced that a rat on this table could not reach it. The food, however could be reached from table number 2, the top of which was connected by a bridge with the food holding part of the top of table number 1 (see figure 2.2). When rats, trained for the two activities, were released on table number 1 out-side the fence around food, they readily climbed down from the table to the floor, scrambled on the floor to reach the ladder with the table number 2, climbed up this ladder, and, using the bridge, reached the food. Seemingly the rats were using elements of the past experience to solve a new problem.

Another example: young chimpanzees in captivity play with different objects variously. If in their enclosure there are empty packing boxes, they would arrange them on one another. If bamboo sticks are available, they would "eat" around an end of a stick to make it thinner, and try to fix this end into hollow of another stick to make a longer pole. During the World War I Kohler observed that his captive chimpanzees would climb on a packing box to reach a banana, suspended from the ceiling. If one box was not enough to reach the food, it would put another over it, and, if necessary, a third one, and then climb over boxes and get the banana. Similarly, if a banana were lying on floor out-side the cage, the captive chimpanzee used a bamboo stick to rake in the fruit. If one stick was not long enough to reach the banana, the animal would join to-gether two sticks to make a longer rake. Seemingly the Kohler's chimps were using elements of behaviour, learnt earlier during play, to solve new problems.

Nonhuman and human intelligence also includes the property of forming principles on basis of experience. Jane Goodall has put on record the story of a gorilla tribe in East Africa that avoided jeeps and cars years after one young gorilla had been shot at and killed by somebody on a jeep. As Goodall has pointed out, this observation suggests a communication system in the tribe. It also suggests that a principle had been formed in the tribe, that automobiles were too dangerous to be nearby.

FIG. 2.2: Diagram to illustrate an experiment with rats. Results of the experiment show that rats may use elements of past experiences to solve a new problem. For details see the text.

Conceptual thinking, consciousness and in-sight

Conceptual thinking or symbolization, that is concept or symbol formation, is a characteristic of human intelligence. These symbols may be expressed in an articulate series orally or by writing with hand on a flat surface. The former way of expression has led to speech and language, and the latter to writing and literature. These expressions have been of vital importance in communication in human society. There are some indications of this that apes too are capable of concept formation and articulation, though only to a small extent.

Another peculiarity of human intelligence is consciousness, the nature of which has been much debated. Roughly by consciousness we mean self awareness and self evaluation. The various attempts to explain consciousness fall under two categories, those which ascribe the phenomenon to a life force or soul, which is apart from the body, and whose presence in the body is necessary for life and consciousness, and those, which regard consciousness as a nervous phenomenon, as due to a highly evolved and intricate arrangement of synapses. The first category of explanations amount to metaphysics, an area out-side the scope of the present treatment. The other category of explanations seem to have a scientific basis, as the role of neurons and synapses in sensory perception, neural integration and in mediating motor responses are well established, though it has so far not been possible to adequately explain the mechanism of memory, reasoning and consciousness. Consciousness seems to have evolved gradually, as even primitive forms, like fishes and crustaceans, have proprioreception and statoreception, i.e. perception of body's own movements and of orientation of the body with reference to the direction of gravity respectively.

Of late the concept of voices, internal and silent in the mind shaping consciousness, has been gaining acceptance among psychologists. Lev Vyogotsky, a Russian psychologist, noted in 1930s that children, between 2 and 7 years in age, often take to self-addressed audible speaking, organizing their thoughts and planning. Later, when it has become well practised, this habit of self-addressed speaking become internal and inaudible mental working and consciousness. Psychologists regard this inner voice as memory and reasoning aided by the acquired language. Language audibly spoken, written or internal and inaudible, helps in carving out concepts.

But then earlier it has been said that language is a product of conceptual thinking. Now it is being said that language helps in making of concepts. Are the two statements not mutually contradictory? Well, the situation is roughly analogous to that of making tools, which then can be helpful in making more tools, including advanced ones and complex machines. After a growing human individual has acquired a good grip on a language, the language greatly helps him in concept making, reasoning, planning and making decisions. Perhaps ancient Hindu philosophers had realized the significance of language in learning and concept making, and that is why they gave the name "VANI" (=speech) to Saraswati, the goddess of learning and wisdom.

Besides the internal "audio" human mental working also includes an internal "video". A support for this notion: forms, preserved in memory, appear in varying sequences in dream.

Now let us turn to "in-sight". By "in-sight" is meant internal visualization of a problem and its possible solution. A good illustration of this is provided by classical and simple psychological experiments on "detour". One such experiment is shown in the figure 2.3. A mammal, say a jackal, has been tied with a cord, which at its other end has been tied to a pole, the pole number 1. The cord goes round an obstacle, say a pole, the pole number 2, before reaching the animal. When the animal is in position shown in the figure, it is exposed to food kept in such a position that the animal can reach it only when the cord does not go round the pole number 2, and is fully extended. How will the animal reach the food? We may think of three possibilities:

(a) The animal either altogether fails to reach the food, or runs about excitedly and solves the problem by "accident".

(b) It solves the problem by trial and error. On repeated exposure the animal may learn to solve it in fewer attempts or even in a single attempt.

The third possibility obviously speaks of in-sight. Only primates among mammals show some degree of success in solving the problem of getting to the food in one attempt on first exposure.

FIG. 2.3: Diagram to illustrate an experiment on "detour". Only Primates sometimes are able to solve the problem of reaching the food on first exposure i.e. without trial and error.

Social Memory

In humans, and to a small extent in mammals and birds too, experience of previous generation is passed on to the developing generation through a long post-natal care and education. This socially accumulated experience and learning or social memory plays a very important role in shaping behaviour. The human capacity of symbolization or conceptual thinking, leading to language, writing and literature, has had a great impact in development of social memory in humans.

Concluding remarks

The special features of human intelligence, enumerated and discussed above (but for social memory), obviously depend to a large extent on the genetic make-up. But basic learning, through conditioning, imprinting etc., and acquisition of knowledge and skill through social memory depend mostly on environmental exposure. It is known now that in a child between the age of four and ten years a large number of synapses in the brain disappear. How many brain synapses survive in this phase of development has a relation to the extent and variety of learning experience, to which the child is exposed. Thus development of intelligence in Man has a strong genetic basis, and at the same time environment too plays a significant role in this.

Human intelligence, in association with social memory and technology, has led to development of civilization, which, besides being a unique and wonderful phenomenon, has been causing a heavy drain of resources on the earth, and has been responsible for extinction of a large number of animals and plants. It is high time that we intelligently evaluate human intelligence for its advantages and limitations, and plan and execute steps to minimize further damage to the biosphere.

3. EVOLUTION OF MODERN MAN

Introduction

Human evolution is quite a common topic in text-books of zoology and anthropology. The topic, chosen for this essay, is somewhat different. The present Man is Homo sapiens as per zoological nomenclature. How, where and when this species evolved from early and more primitive members of the human family, Hominidae - this is the central question for the present discussion. But, as a prelude to this discussion, we may summarily recall the history of evolution of Hominidae.

Evolution of Hominidae

Members of the primitive primate subfamily Dryopithecinae were generalised apes, living in Miocene and Pliocene (i.e. more than 15 million years ago) in Europe, Egypt, South Africa, India and China. They are believed to have been common ancestors to the present day apes (Family Simiidae) and the family Hominidae. Earliest hominids, known to us, are Australopithecines (also referred to as Man-apes) from Africa. Oldest australopithecine fossils are about 3.5 million years old, and they seem to have become extinct about 1 million years back. A primitive australopithecine, like Australopithecus afarensis, discovered and described in 1974 by the American palaeoanthropologist Donald C. Johanson, is regarded as having been ancestral to the genus Homo, which includes the present day Man. Early fossils of Homo have been called pithecanthropines. Technically they are Homo erectus (in common reference ape-man). Their remains have been discovered in North China, Europe, all over Africa and warmer parts of Asia (Eckhardt, 1979). They appeared 700,000 years back, and were widely distributed 300,000 years ago. Some African pithecanthropines have been estimated to be 1 to 1.5 million years old. They seem to have become extinct nearly 100,000 years ago.

The pithecanthropines, specially the earlier ones, in their various features, were quite intermediate between autstralopithecines and the modern Man. Hence the former are regarded as having been ancestral to the latter.

The pithecanthropines are believed to have been progenitors of another species of man, the Neanderthal Man (Home neanderthalensis), who lived in Europe, Middle East and North Africa, and disappeared about 25,000 years ago.

This summary of human evolution is illustrated in figure 3.1.

FIG. 3.1: Evolution of the human family, Hominidae, shown diagrammatically. Note that the Neanderthal Man (Homo neanderthalensis) and the Modern Man (Homo sapiens) are believed to have evolved from Homo erectus almost independently.

The central question

Now let us return to the central question : how, when and where did the Modern Man evolve? The first two parts of the question are not very difficult to answer. As has been pointed out above, early pithecanthropines are regarded as progenitors of the Modern Man. In fact pithecanthropines were already quite similar to the present day Man. Some more directional changes in acquisition of erect posture, larger brain, receding of jawa etc., in response to continued similar selection pressures, and it would be the Modern Man. As an example of directional nature of the changes, comparative cranial volume in higher primates is shown in Table 3.1.

Table 3.1: Comparative Cranial Capacity In Higher Primates (After Mayr, 1963)
Primate Cranial capacity
Larger apes (Chimpanzee and Gorilla) 325 to 650 ml.
Australopithecines 450 to 650 ml.
Pithecanthropines (Java Ape Man) 800 to 1000 ml.
Pithecanthrpines (Peking Man) 900 to 1100 ml.
Modern Man 1200 to 1600 ml.

The earliest fossils of the Modern Man (Homo sapiens) are known from the Klasies River Mouth Cave and the Border Cave in South Africa, and from caves at Skhul and Qafzeh on the Mount Caramel in Israel. Using modern techniques of dating relics, these remains have been found to be nearly 1,00,000 years old. Bones of anatomically Modern Man have been found in Kenya and Ethiopia. They have been dated as 70,000 years old or more. Middle palaeolithic culture is associated with early Modern Man, and earliest tools of this culture have been dated as about 1,30,000 years old. Hence it is believed that about 150,000 years back modern Man existed, and that about 200,000 years ago two lines of descent arose from a Homo erectus stock and led to Homo neanderthalensis and Homo sapiens (Stringer, 1990).

Now let us turn to the remaining part of the question - where did the Modern Man evolve? It is quite a vexing part of the question, and it is important because it has some bearing with racial prejudices. Next part of the essay is devoted to this problem.

FIG. 3.2: Diagram to illustrate the Multiregional Model.

Place of evolution of the Modern Man

We are far from having reached a satisfactory solution to this query. Three main solutions have been suggested, which have been referred to by Stringer (1990) as the Multiregional Model, the Gene-flow or Hybridization Model and the African Model.

According to the Multiregional Model the racial features of any race have taken long to evolve. They have evolved in the region, in which the race is found, independent of racial evolution in other regions. Thus descent of races has taken place independently in different regions from the Homo erectus level. In other words, the Modern Man has been polyphyletic in origin, and, therefore there are several quite different and distinct human races in different geographical areas. Exceptions to this situation are areas, where recent migrations have occurred. For example, the North American continent is inhabited by American Indians, Europeans, Africans and also Asians. This model has been expressed by a number of palaeoanthropologists. A recent supporter is M. H. Wolpoff.

The Gene-flow or Hybridization Model is similar to the Multiregional Model, with the addition that there have been genetic exchanges through interbreeding between the different lineages. Such interchanges are believed to have become more frequent as Homo sapiens was evolving. Thus the Modern Man, as per this model, has evolved through a web of lineages. Erik Trinkaus and F. H. Smith are supporters of this model.

The African Model suggests that the Modern Man arose in Africa from a stock of Home erectus, and then migrated from here to the Middle East, and subsequently to other lands. The populations of Homo sapiens, settled in different parts of the world, due to continued selection in somewhat different directions, developed their own characteristics and became different geographical races. Thus, according to this model, Homo sapiens has been monophyletic in origin, and differences between races are not such deep clefts in their phylogeny or ancestral history as is suggested by the other two models.

Several recently discovered evidence favours the African Model. Hence most Zoologists and Anthropologists to-day find this model more acceptable than the remaining two. Now let us briefly examine the evidences, which have been provided mainly by three areas of study, viz. genetic studies, palaeoanthropological studies and language studies.

FIG. 3.3: The African Model of origin of Modern Man. (Arrows indicate initial migrations.)

Evidence from Genetic Studies

DNA, the genetic material, has been studied in different humanpopulations. In a human cell, as in cells of all higher organisms, two types of DNA are found, nuclear DNA or n-DNA, which is in nucleus and chromosomes, and mitochondrial DNA or mt-DNA, which is the DNA found in respiratory organelles or mitochondria.

From the present view-point mt-DNA is specially suitable for study. It is inherited only from the maternal side, and, therefore there is no mix-up of maternal and paternal DNAs during fertilization and formation of a new individual. Due to these circumstances inheritance of mt-DNA is a simple lineage, theoretically traceable to a single woman far back in past. Allan C. Wilson and his group of workers have used mt-DNA as a molecular clock. They have comparatively studied a segment of mt-DNA in different human populations, and have tried to imagine the ancestral condition, and have studied accumulation of mutations in the chosen segment of mt-DNA in different populations. Keeping in view the present rate of mutations in the mt-DNA segment, and presuming that this rate has been consistent throughout, they have tried to work out how long a particular population has been evolving beyond the ancestral condition. Main inferences of their study : (1) that the mt-DNA has been evolving for the longest period in Africa, to be more exact in the Khoisan or Bushman population, (2) that it has been evolving in certain Homo sapiens populations in Africa for nearly 1,50,000 years. This estimate agrees so well with inferences from Anthropological studies.

n-DNA has been studied in human populations to solve the problem, under discussion, from two standpoints, viz. through expression of certain genes and by preparing DNA profiles. Studies on these lines have been based on the principle that greater the period of separation between two populations greater the difference in their DNA. It will happen even if there is no natural selection; it will be through random mutations and genetic drift.

Cavalli-Sforza of Standford University, USA, and his colleagues Menozzi and Piazza have studied frequency of some 100 genes (e.g. the gene for Rh factor) in 1800 different populations, each sample consisting of several hundred individuals. It was a 12 year project (Cavalli-Sforza, 1991). Their results clearly suggested that the genetic distances between Africans and non-Africans were greater than in any other inter-continental comparison.

DNA profiles or DNA finger printing for different populations have been studied by Cavalli-Sforza and also by Kenneth Kidd and Judith Kidd of the Yale University. From these studies the inferences, in words of Cavalli-Sforza (1991), are, "The genetic distance between Africans and Non-Africans is roughly twice that between Australians and Asians, and the latter more than twice apart than between Europeans and Asians. The corresponding times of separation suggested by Palaeoanthropology are in similar ratios....."

Evidence from Palaeoanthropology

Earliest remains of the Modern Man are known from the caves at the mouth of the river Klasies in South Africa. They are nearly 100,000 yearsold. From 1930 onwards in a number of caves in the Middle East human remains have been found. They seem to be remnants of burials. At some places indications of burial rituals have been discovered. In an Iraqi cave, called Shanidar, remains of a man, two women and an infant have been found. The relics are about 100,000 years old, and pollen of early spring wild flowers have been noted around the human remains (Anonymous, 1996).

Two caves, those of Skhul and Taboon, in Israel have been found to hold very old human skeletal remains. The fossils at Skhul have been identified as of early modern humans, and, using reliable modern techniques, have been dated as nearly 100,000 years old, and those at Tabun as of Neanderthal Man and about 120,000 years old. Nearly 1,00,000 years old remains of the Modern Man have been dug out also at Qafzeh. Neanderthal fossils, dug out at Kebara, have been estimated to be nearly 60,000 years old.

Thus earliest remains of the Modern Man, Homo sapiens are known from South Africa and also from that part of the Middle East which is close to the present location of the Suez Canal. Very early Modern Man's remains (70,000 years old or more) are also known from East Africa. These finds suggest that the Modern Man arose from the Homo erectus level either in South-east Africa or in the Western part of the Middle East (figure 3.3).

In the foregoing account the Neanderthal Man has been mentioned. This species has been so named because its fossils were first discovered in the Neanderthal Valley in Germany. The species presents a number of specialised features, such as heavy brow ridges, flat skull roof or platycephaly, large cranial capacity, even more than in the Modern Man, and cheek bones presenting out-ward angles. They are believed to have been quite intelligent, and having their own primitive culture and language.

We are still not quite clear about Modern Man's relations with the Neanderthal Man. In Europe the Neanderthal Man appeared first, and Homo sapiens later. Hence it has been often suggested that the former was ancestral to the latter. But as we have noted above, the Neanderthal Man with his specialized features was present not only before but also after the modern man appeared. Hence now generally the Neanderthal Man is not accepted as a progenitor of Homo sapiens, confirmed by mitochondrial DNA sequencing.

In Europe primitive Homo sapiens, called the Cro-Magnon Man, appeared about 40,000 years ago, whereas in the middle East and also in Africa, who were living even nearly 100,000 years ago. In Europe the Neanderthal Man lived and had acquired Neanderthal characteristics about 125,000 years back. Nearly 10,000 years after appearance of the Cro-Magnon Man, that is nearly 30,000 years from now, the Neanderthals disappeared. We do not know what happened to them. One suggestion is that they interbred with Modern Man and lost their identity. But Stringer (1990) points out, "The Kebara Neanderthal (i.e. the Middle East Neanderthals, some specimens of which have been discovered in the Kebara Cave) may have lived 40,000 years after the two populations (i.e. the Neanderthals and the moderns) could have come in contact, yet this specimen (i.e. the Kebara specimen) shows no signs of hybridization with the modern humans - in fact it is one of the most robust and characteristic of Neanderthal skeletons." Similarly human remains, discovered in the Middle East, 30 to 40 thousand years old, show no sign of hybridization between Neanderthals and moderns.

In view of these facts it is generally accepted now that the Neanderthal Man was a different species from the modern. It is further believed that the pithecanthropines (Homo erectus) gave rise to Homo neanderthalensis in Europe, and to Homo sapiens in Africa/Middle East. How did the moderns replace the Neanderthals in Europe and Middle East? Perhaps they proved superior to Neanderthals in competition. Anonymous (1996) pointed out the possibility that "That (the moderns) survived the glacial cold as they were equipped with better shelters, tailored clothing and more efficient hearths". Anthropological finds indicate that the Neanderthals had fairly well developed stone age culture, but moderns were culturally more advanced.

Palaeoanthropological studies suggest separation between Africans and Asians about 100,000 years ago, between Asians and Australians nearly 50,000 years back, and between Asians and Europeans about 35,000 years ago. Thus separation between populations of moderns, in different areas is in the same proportion/ratio as genetic distances between them (vide supra).

Another significant inference from such studies : fossil record of hominids about 300,000 years old indicates close relation between populations of Europe and Africa on one hand and of China and Indonesia on the other. By about 100,000 years ago hominid populations in different regions looked quite different. Now there were Neanderthals in Europe and West Asia, modern humans in Africa and West Asia, Homo erectus and other primitive forms in China and Far East. 20,000 to 30,000 years from now very much similar primitive moderns were inhabiting Europe, Asia and Australia.

Evidence from Linguistics

Languages have been evolving with people. Some linguists have tried to prepare evolutionary tree for world languages. There is a remarkable correspondence between an evolutionary tree for languages and an evolutionary dendrogram for human populations based on genetic distances between them (Cavalli-Sforza, 1991). This situation attests the naturalness of the tree based on genetic distances and showing origin in Africa.

It may well be asked why there should be correspondence between a genetic tree and linguistic tree, when we know that it is not the genes which decide the language one speaks. One's tongue is decided by the environment in which one grows up. That even then there may be correspondence between the two evolutionary trees is explained by Cavalli-Sforza (1991) as follows. Genes are inherited from generation to generation, that is in a vertical manner. Language on the other hand is learnt both from the parents and also from the members of the same generation, that is both vertically as well as horizontally. Horizontal language learning is more pronounced in urban areas. Adoption of language of another population due to cultural or political invasion is also more marked in urban areas. On the other hand vertical learning of language is more pronounced in rural areas. Linguists, keeping in view this situation, have mostly confined their study among tribals and aborginals.

If a population gets divided into two parts, and the two move into different areas and become isolated from each other, the two isolated parts will become genetically somewhat different due to evolution taking place in a little different directions. Their language may also become somewhat different due to local influences. But both the gene pools as well as their languages will retain the same basic structure/constitution as at the point of bifurcation. Thus courses of genetic and language evolution are close and parallel. This explains why there should be correspondence between linguistic and genetic trees.

Thus the African Model is gaining ground, and we are inclined to believe in African and monophyletic origin of the Modern Man, and in that the races of Homo sapiens are local and geographical races.(In a symposium, held in October 1997 at the Cold Spring Harbor Laboratory, New York, geneticitsts, who had before them an immense amount of data regarding human populations, upheld the African Model of origin of the Modern Man.)

4. APES TO MAN - WHY NOT NOW?

Introduction

Quite a few times we have faced an innocent but baffling question - if Man has evolved from apes on loss of forest cover, and if there are apes at present and also fast receding forests, why apes are not changing into Man now.

The question is baffling because we tend to forget that cases of organic evolution are actually experiments in nature, outcome of the experiments depending on a complex of factors and not on just one or a few factors alone. A successful evolutionary experiment is due to a rare combination of certain favourable factors. On basis of what we know of human evolution, let us try to make out those favourable factors which led to Man descending from apes. Let us begin with primitive apes, which are believed to have been ancestral to Man.

Primitive apes

By primitive apes we are here referring to the apes living in the geological periods Miocene and Pliocene, that is nearly 20 million years ago. Their fossils have been discovered in different parts of Africa and Eurasia, including the Siwalik deposits of India. There are strong indications that the living great apes as well as Man have descended from the primitive apes.

It is important to note that the primitive apes were much less specialised than the present day apes. Mayr (1963) has quoted the following from the anthropologists Le Gros Clark and Leakey (1951) to point to lack of specialised skull features of the modern apes in the apes of Miocene and Pliocene. The anthropologists concluded, "that the characteristic features of the skulls of the African apes of to-day, such as the powerful supraorbital torus, the large circular and forwardly directed orbits associated with a strong development of their lateral margins, the broadening of the lower extremity of the nasal aperture, the extension downward and forward of the subnasal part of the premaxilla, and widening of the symphysial region of the mandible in association with a relative hypertrophy of the incisor teeth, and the development of a simian shelf, were probably all secondary developments which appeared at a later stage of evolution (i.e. beyond the primitive ape stage)".

The present day apes are specialized for brachiating, that is moving from branch to branch by swinging with the help of arms and hands. Their fore-limbs are as a result longer than hind-limbs. It is due to this difference between the two pairs of limbs that, when moving on land on all fours, the body is semierect or stooping forward, and not horizontal as in monkeys. However, this specialised feature, viz. the longer fore-limbs, was not there in the primitive apes. Describing the situation in the primitive ape, Pliopithecuse of Europe, Mayr (1963) points out, "The discovery of some fairly complete skeletons..... has revealed that this form was not yet a specialised brachiator, and that the proportions of the anterior extremities (in relation to the trunk) did not deviate materially from those of man....".

Such primitive and unspecialised apes could be fore-runners of the specialised apes of the present fauna as well as of Man. Specialised forms, like chimpanzee or gorilla, if faced with a large scale environment change, such as disappearance of forests and their replacement with grassy plains, the fate of such animals would be extinction and