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Heredity and Environment: Meaning and Effects!
The Meaning of Heredity:
Man’s behaviour is influenced by two forces: heredity and environment. The biological or psychological characteristics which are transmitted by the parents to their off-springs are known by the name of heredity. Heredity is, in other words, a biological process of transmission of certain traits of behaviour of the parents to their children, by means of the fertilized egg. Heredity traits are innate; they are present at birth.
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The human individual is the progeny of two parent cells that come together when a male sperm fertilizes a female egg. In the nuclei of these parent cells are certain hair like substances called ‘chromosomes’. The chromosomes contain chemical substances called genes. These basic substances, chromosomes and genes determine characteristics of the individual. And this is what constitutes heredity.
The essential characteristics inherited by all human beings are physical structure, reflexes, innate drives, intelligence, and temperament. There are some biologists who claim that the difference in the traits or qualities of individuals or groups are due to the difference in their heredity. They are duly supported by some psychologists and sociologists in their assertion, that like begets like.
But there are others who explain that the variations of human beings and the societies are due to differences in environment. Thus a great controversy has been going on since long about the relative importance of heredity and environment in determining the behaviour of individuals and groups.
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Though arguments have been advanced by the supporters of both heredity and environment, no exact conclusions with regard to the relative importance of the two factors have been drawn, nor is it possible either to determine the relative values of both.
Modern biology has long insisted that we are what our parents and grandparents have made us, that heredity counts far more than social opportunity. Not only it is impossible for a man to change his skin, but he cannot change his outlook, his mode of thinking or behaviour because these too are hereditary. Others, on the other hand, belittle the importance of heredity.
Effects of Heredity:
The main supporters of the heredity theory have been authors like Galton, Karl Pearson, Mc Dougall, and others while the champions of the environment have been G. B. Watson in the United States and other behaviourist authors.
Among the arguments brought forward in support of the preeminence of heredity over environment following are most important:
Galton’s studies:
Galton in his pioneer work on Hereditary Genius (1869) has sought to show that the probability of the occurrence of greatly gifted children is vastly higher when the fathers are of a superior intelligence.
Karl Pearson’s researches:
Karl Pearson had also concluded that the influence of the environment is far less than that of heredity in determination of importance of human differences. According to him, it was possible to measure the relative efficiency of the two. He had given evidence to show that for people of the same race within a given community heredity is more than seven times more important than environment.
Groups of higher intellectual rating produce more persons of genius:
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Like Pearson many other researchers have shown that the groups with the higher social or intellectual rating have produced more persons of genius or distinction. For instance, royal families produce in proportion more geniuses than others, families of the clergy in the United States produce the largest proportion of notable men, followed in order by the other professions, businessmen, farmers, labourers and so on.
Difference in intelligence levels of different occupation groups:
Some writers have brought out considerable differences between the intelligence levels of different occupation groups. For instance, it has been found that the children of professional parents had an intelligence quotient of 116; those of semi-professional and managerial classes 112; clerical, skilled trades, and retail business 107.5; semi-skilled, minor clerical occupation and business 105; slightly skilled 98 and finally, the children of labourers, urban and rural farmers 96.
But all this is not necessarily due to heredity. These are no doubt important facts but conclusions drawn from them appear to be superficial. They simply give evidence regarding a common observation: that those who are born in the families possessing distinction are more likely to develop intellectual and other attainments. But these facts tell us nothing how these differences are attributed to heredity.
It is clear that the persons engaged in these experiments must be having strong prejudices in favour of heredity. Further, we know nothing of the equipment of the parents themselves but only their degree of success in life and even the criterion of success could not be a rigid one. Again, the environments for the children of different classes were quite different. The children of the upper classes had definitely better educational and other facilities.
There is then no reason why they should not be more intellectual. Not only the biologists assume that the traditional behaviour of a population is accounted for physically, but they are unwilling to study the variability of human behaviour under different social conditions. All the evidence available argues against the theory that a people must conduct itself in a certain way merely because of its physique. Even identical twins, when brought up in different environments, behave differently.
Intelligence scores of Negroes and Whites:
Various studies of the comparative intelligence of Negroes and Whites have been made in the United States through the application of psychological’ intelligence tests and it has been found on the basis of these studies that the Whites have higher intelligent scores than Negroes. For instance, the tests applied to Army recruits during World War I had revealed the average mental age of Negroes as 10.4 years and of the Whites as 13.1 years.
These facts are also open to criticism. It is true that Whites surpass Blacks in meeting intelligence tests; but how good is the evidence? Firstly, intelligence tests may not be valid tests for determining the degrees of general intelligence because they are simply knowledge tests or indirect measures of scholastic aptitude. Secondly, these tests do not take into account differences of the cultural background of the two groups.
The background of the Negroes usually differs from that of Whites. Thirdly, there is no certainty that these tests have been conducted with impartiality or objectivity. Fourthly, even if the intelligence is there, it is not to be attributed to hereditary or racial differences alone as we cannot ignore the factor of differential environment. The influence of differential training,, experience, home life, social opportunity, economic disadvantage etc. definitely have their influence in the matter.
That is why the Negro children in the North who have better facilities of schooling etc. make higher scores than do those in the South. We can thus safely conclude that intelligence tests are only measures of accomplishment and not of innate racial differences in mental ability. They are useful as showing differences that exist in intelligence of different groups but they are in no way the means to assess heredity.
Man is a highly unstable animal. He is changing-visibly changing. The change in social behaviour of man is on account of change in his environment. The records of crime tell that, in the end, the environment is irresistible. If a second generation is more criminal than the first, the explanation is to be sought in the difficulty of overcoming social and economic obstacles.
Physical traits and heredity:
The protagonists of heredity are very much emphatic in attributing the differences in physical traits among different nationalities to heredity. The average height of a Japanese soldier is 63.24 inches and that of an American soldier is 67.51 inches. But we should not assume that such figures correctly measure the heredity difference. The view point that physical traits are the product of heredity is also falsified when we consider the effect of environment.
The conditions of life, the kind of food, of nature, of climate etc. have definitely their influence on them. There is, in fact, convincing evidence that when children are subject to unfavourable conditions, their stature, as well as the weight is affected. Similarly, it has been shown that American born children of immigrants, especially among Jewish and Japanese groups, not only grew to an average height of two inches more than parents but even experienced changes in head formation.
Thus it is clear that heredity alone is not responsible for the physical differences between national or racial groups and that environment has also its influence. Rather stature or the general build up of the body depends upon innumerable factors which play their part from the moment of conception. The mother’s health, gland disorders, food habits, climate, living conditions, occupation, exercise, modes of walking and sleeping all influence the body structure.
Further it has been proved by certain studies that a child inherits some qualities which may be latent in his parents but are present in grandparents. Heredity is, therefore, to be considered not in terms of a single generation but in terms of several generations and so is the case with environment. This is clear from the fact that the general stature of European people has increased since the days of the armored knights and American college students today are taller and heavier than those of two or three decades ago.
Studies of some families:
The classic studies in heredity are those of the Jukes, the Edwards and the Kallikaks. The study of the Jukes was made by R. L. Dugdale, of Edwards by A. E. Win ship and of the Kallikaks by Henery H. Goddard. Dugdale gathered data regarding members of the Jukes family for the yea. 1800-75 and found that the family had contributed to delinquency, crime, pauperism and disease in the state of New York.
It was revealed that of the 1200 descendants 440 were physically defective or diseased, 310 were paupers, 130 had been convicted of crimes and seven condemned as murderers, and perhaps more than half of the women were prostitutes. On the other hand, A. E. Win ship undertook the study of the Edwards family. His account was published in 1900. It showed that out of 1394 descendants more than 295 were college graduates among who 13 came to be college presidents and one, a vice-president of America.
Some were clergymen, physicians, officers of the Army and the Navy, authors, lawyers, judges, governors etc. In 1912 Henery H. Goddard made a study of the Kallikak family. Martin Kallikak through illicit relations with a feeble minded girl became the father of a line of defectives – 480 in all. Later Martin Kallikak married a respectable girl: the 495 descendants of this marriage all turned out good.
According to Goddard, the Kallikak family presents a natural experiment in heredity. A young man of good family. Martin Kallikak, became through two different women the ancestor of two lines of descendants the one characterized by thoroughly good, respectable, normal citizenship; the other characterized by mental defects.
The conclusion drawn from these studies was that it was heredity and not environment which was the decisive cause of the difference of behaviour in these families. But we should not be prepared to accept the accuracy of the conclusion as the study suffers from many defects. In the first place we must ask in what sense are the Jukes and Edwards of the present generation the same families as those of nine or ten generations back.
Each generation is a fresh admixture and the blood of countless admixture flows in each of us. The names of prominent ancestors are borne by many persons who possess none of their chromosomes or hereditary traits in the biological sense.
Further both the Edwards and the Jukes married persons from other stocks but as parent communicates to the offspring only one of his or her chromosomes we have no reason to assert that the heredity of the descendants of the Edwards or Jukes was the same as that of the head of the branch.
Moreover, as the total number of descendants from both families is unknown we cannot assert for certainty that all the Edwards were good and all the Jukes degenerates. Rather subsequent investigations on the Edwards families showed that a certain Elizabeth Tuttla, the grand-mother of illustrious Jonathan Edward, had been guilty of adultery and immorality, her sister murdered her own son and she herself was killed by her brother.
The number of descendants of Elizabeth Tuttla must have been near about 90,000 out of which the number of celebrities has been very small. Above all, the environment in which the unearthed members of both the families lived was very different.
The Edwards were searched for and found in distinguished homes and a highly favourable surrounding while the search for Jukes was made in poor degraded environment. Had the Jukes been reared in favourable environment, they would have risen perhaps as high as the Edwards.
Even in the writings of Dugdale, Win ship and Goddard are interspersed the statements that suggest a preponderant role of environment of social participation, in the efficient functioning of some of the cases studied by them. These studies may thus be of interest but as evidence of heredity, they are now being discredited. Hogben said, “If social biology ever becomes a definite science the interesting history of Jukes will be viewed as we today view Alchemy.”
Controlled Experiments to Determine the Respective Role of Heredity and Environment:
The Sociologists have, for sometimes past, been making controlled experiments to solve the nature—nurture problem, and to ascertain the influence of environment over heredity or vice-versa. They have held one of the factors as constant and the other varied, on the principle that the differences so revealed can be attributed solely to the variant factor.
For instance, children of the same heredity i.e., twins have been put under different environments and the differences in their behaviour have been consequently attributed to environment. Conversely, children of different heredities have been placed together under the same environment and the differences in their behaviour have been attributed to their heredity differences. Below are given some of such studies.
Environments on twins reared together and apart:
Galton had experimented with “identical” twins and had found that they exhibited marked similarity in their behaviour. He had been convinced that heredity played a dominant part in the causation of both human resemblances and human differences.
The subsequent researches have also established that twins exhibit closer resemblances, physical and mental, than siblings who are not twins; and that, particularly with respect to certain physical traits; identical twins are more alike than fraternal twins. But these conclusions have been found to be incorrect in the researches recently made.
No doubt some close similarities between identical twins have been found but there have been significant differences also. The most famous experiment of this kind is that of the Dionne identical quintuplet sisters of Canada. The five sisters were reared in the same environment from their tender years but they had shown marked differences in personality and temperament.
Again studies have been made of identical twins reared in different environments by H. H. Newman, a biologist, F. N. Freeman a psychologist and K. J. Holzinger, a statistician. They studied nineteen pairs of identical twins brought up in separate homes. They concluded on the basis of their observations that physical traits are least affected by the environment, that achievement and various skills are somewhat more sensitive to environmental influences, and that personality characteristics are most affected.
Experiments on children under same environment:
Miss. B. S. Burks studied the case of children of different heredities brought up from infancy in the same foster home. She came to the conclusion that heredity’s contribution was about 80% and that of environment about 17 to 20%. But this conclusion has not been widely accepted. It is surprising as to how she could correctly measure the contribution of innate ability or achievement.
On the other hand, a study conducted about the same time by F. N. Freeman showed that the character of the foster home definitely affects the degree of intellectual ability attained by the children subjected to its influence. Similarly, the investigations over 150 children, mostly illegitimate, conducted at the University of IOWA by H. M. Skills indicated that intelligence is much more responsive to environmental changes.
The conclusions of the above studies take us nowhere. They fail to measure exactly or approximately the potency either of heredity or of environment in determining the difference of human behaviour. All efforts regarding the relative amounts of heredity and environmental influence seem to be wasteful.
One writer has rightly remarked: “The whole array of twins studied seem to suggest the futility and artificiality of the idea of disentangling nature and nurture influences in the sense of asserting the percentage contributions of each in any general sense.” While it is true that the races of mankind certainly differ—because of heredity—in such matters as hair form, stature and colour of the skin, it is difficult to say how significant these stature differences are for the social life of the various races.
Does the straight round hair of the Chinese make Chinese society different from that of the Negroes with flat wavy hair? People with the same hair form have societies as different as those between the Negroes and Chinese. Variations in human behaviour are not likely to be explained satisfactorily by variations either in heredity or environment.
Heredity and environment are not separable:
The problem of nature versus nurture defies satisfactory solution. As a matter of fact, it is futile to ask which of the two factors, heredity or environment, is more important. According to MacIver, “Every phenomenon of life is the product of both, each is as necessary to the result as the other, neither can ever be eliminated and neither can be isolated.” No society is a product of environment alone for men inherit physical heritage.
The truth of the matter is that there is incessant interaction between the two. They are inseparable. One man is a law-abiding citizen, another is a criminal; one a militarist and another pacifist. It is difficult to indicate any genetic basis for these variations and in many cases it is almost impossible to assess properly the relative role of heredity and environment in producing these differences.
Both have been operative to produce every particular situation since time immemorial. In no case of personality development can we properly attribute any characteristic to heredity or to environment alone. A given result is always produced by the interaction of gene substance, and their environment. We should not, therefore, be interested, in asking about the absolute contribution of either factor as a whole.
In Altenberg’s words, “Each trait requires both heredity and environment for its development.” Lumley said, “It is not heredity or environment, but heredity and environment.” We have no more justification for denying the importance of heredity than some eugenists have for denying the importance of environment.
Heredity, no doubt has its influence on the physiological traits but environment is also the arbiter of our development. What heredity can do environment can also do. Neither can ever be eliminated and neither can ever be isolated. Both have been operative in determining human behaviour. An immigrant group, no matter what its heredity antecedents, exhibits new characteristics when transplanted from its native land to the country of its adoption.
Heredity is of no avail if environment is not there to show it off. For instance, it is the industrial age which has made possible for men of talent to rise to eminence that otherwise could have remained in obscurity. A new social situation or a happy chance may thus give a genius the opportunity to reveal his power but no amount of favourable conjuncture will turn a person of mediocre mentality into a genius. David Abrahamson has written that heredity determines what a person can do, and environment what he will do.
The capabilities of man are hereditary, but their manifestation is the work of the environment. According to Landis and Landis, “Heredity gives us the capacities to be developed but opportunity for the development of these capacities must come from the environment.
Heredity gives us our working capital; environment gives us opportunity to invest it. Heredity explains man the animal, environment man the human being.” In the words of Biesanz and Biesanz, “Personality is the organisation of a person’s attitudes, habits and traits and arises from the interplay of biological, social and cultural factors.”
The conclusions that we can draw from the above discussion is that the question, “which is more important, heredity or environment?” wrongly assumes that environment and heredity are opposed, so that if one is important the other cannot be. All the qualities of life are in the heredity, all the evocations of qualities depend on the environment. In other words, heredity has potentiality and environment offers it a chance of bringing them out.
It also follows from this principle that the higher the potentiality, the greater is the demand made on environment. Thus more subtle differences in environment may have little effect on those of low potentiality while the same differences may be vastly significant for those who have higher potentiality.
For instance, a seemingly minor change in a situation, say, a rebuff, may prove decisive to a sensitive nature while it may not affect a thick skinned; man. Lastly, the more elastic the life the more is it at the mercy of environment. That is why environment affects us most in the earlier years of our life when we are most impressionable.
We should thus conclude this controversy of nature versus nurture by accepting the unchallengeable truth that heredity and environment—the two ultimate determinants of every living being- are of coequal importance and that none is more potent than the other.