HUMANICS AND GENETIC ENGINEERING, by Joshua Lederberg, Stanford University condensed from the 1970 Yearbook of Science and t Humanics is defined in the dictionary as the scientific study of human nature. It tells something of our past traditions that the word is an unfamiliar one; but the subject it describes is inevitably caught up in the recent rush of progress in experimental biology. In particu- lar, dramatic advances in our knowledge of the biochemistry of de- oxyribonucleic acid (DNA) and of its function as the material basis of heredity have provoked much new speculation about the applica- tion of this new knowledge to man and his problems. (See 7969 Britannica Yearbook of Science and the Future, Feature Article: THE LANGUAGE OF LIFE.) As a result of these advances, we antic- Ipate better tools to mitigate disease, to improve agriculture, and to exploit microorganisms in industry. ‘ We must also visualize, however, the impact of genetic engineer- ing on humanics, which includes the possible modification of hu- man nature toward previously unattainable ideals. Phrases like “genetic programming” or “genetic engineering’ may conjure up the Frankensteinian image of a mad scientist or a technocratic dictator pushing the buttons that will control an assembly line of babies produced to order for service as infantrymen or storm troop- ers or docile subjects. Some may even imagine that their own genes may somehow be subjected to alteration at someone else’s com- mand or, alternatively, that they will have unlimited options to create- any manner of offspring they wish—perhaps a child who might grow up as an athletic prodigy with an IQ of 350 and a head of hair that automatically shears itself at regular intervals. Actually, our Present knowledge of genetic science is not the obvious limiting factor for the furtherance of such aims. Rather, we lack the neces- sary insight into the essential biochemistry, developmental biology, psychology, and social dynamics of these phenomena, And indeed, were we to gain such insight, genetic engineering would probably be a redundant tool in competition with many other ways of influenc- ing human development and behavior. To avoid the distorted view of genetic engineering that is all too prevalent in contemporary journal- ism, the topic must be examined within a broader view of man's evolutionary history and of the impact of established institutions on human biology. he Future (Encyclopaedia Britannica) — 5 Unconscious genetic engineering Genetic engineering has, nevertheless, been an important element in human cultural progress. The beginnings of agriculture depended on the remarkable insight that the seeds of a given plant would beget others like it. Early agricultural man, in his development of crops like Indian corn and wheat, accomplished technica! miracles that have still to be surpassed by contemporary plant science. This kind of “biological engineering"—to produce reliable food crops from wild grasses—achieved a phenomenal result without the benefit of pro- found insight into the mechanism of heredity or the chemistry of DNA. The prescientific domestication of animals such as the dog likewise speaks for an uncanny shrewdness on the part of early man, We have no way of knowing whether prehistoric man consciously applied similar principles to guiding his own evolution by selective breeding. In many subhuman primates the social hierarchy does give a dominant male privileged access to receptive females during their intervals of maximum fertility. With the development of demo- cratic ideals, however, the very concept of compulsory selective breeding as a method of engineering human improvement has been discredited as a violation of elementary human rights. Nevertheless, the whole social fabric constitutes a pattern of genetic engineering of human qualities more or less consciously intended to prevent deviance from the established norms of a given community. Racial characteristics may just as likely have been conserved by cultural discrimination against deviants and strangers who displayed differ- ences in these obvious features. Other customs, like monogamy, primogeniture, prohibitions against incest, nationalism, war, and commerce have played their part in the de facto policy of genetic engineering of the human species. Very few new techniques for genetic engineering have been firmly ‘established, although there are many important innovations in early prospect. Genetic analysis has, however, helped to expose the ac- tual practices just summarized, and to point out that they do con- stitute a pragmatic social policy of human reproduction, whether ‘or not this was arrived at by conscious legislation. Genetic ciseases The principal utility of genetics in modern medicine is in diagnosis, now applicable to many specific genetic diseases with great preci- sion, mainly by the use of biochemical and of microscopic methods. It is often possible to counsel the parents in a family where a rare disease has cropped up about the prospects of a similar anomaly occurring again in future children. Since many parents will respond to discouraging advice by not taking chances, this kind of genetic counseling is a de facto form of selective breeding. Its principal benefit, however, is intended to promcte the integrity of the family and to prevent the conception of children likely to suffer from a serious defect. A by-product of genetic counseling in this situation is to reduce the frequency of defective genes in the next generation. Because certain deleterious genes can also be detected in the hybrid carrier state, some individuals may use this information in their selection of mates. As yet, we have no reliable statistical in- formation on the subject, but it is doubtful that any significant num- ber of people take genetic faciors into account when they fail in love and marry. From a population-genetic point of view, selective mating does not help to eliminate a deleterious gene from the population; it merely postpones the overt occurrence of defective offspring. Since future generations may well be better equipped to repair a genetic deiect than we are at the present time, selective mating can hardly be called an imprudent policy. The genetic diseases to which such considerations apply are each quite rare, but there are enough of them to warrant the spreading practice of genetic diagnosis in order to furnish significant informa- tion to a considerable proportion of the population. The average human being carries the equivalent of eight or ten potentially harmful genetic defects, all of which are usually masked in the hy- brid condition. Although most of these defects are not now recogniz- able by biochemical analysis, studies of DNA specificity and of cell fusion are beginning to revolutionize our approach to these prob- lems. Cell cultures from specimens of blood or from tiny fragments of skin have enhanced the diagnosis of many genetic diseases. More recently, this technique has also been applied to cells obtained from the amniotic fluid that surrounds the developing fetus. By this method the occurrence of a serious genetic disease in a young fetus can be diagnosed and the mother may request a therapeutic abor- tion so as to avoid bearing a severely crippled or retarded child. (See Year in Review: MEDICINE, Medical Genetics.) A number of genetic diseases can now be detected prenatally. Of these cystic fibrosis, a metabolic disorder in children, is un- doubtedly the most prevalent and, therefore, statistically the most important. Its incidence, however, is too rare to recommend the routine examination of amniotic fluid in every pregnancy. On the other hand, the carrier state for cystic fibrosis can also be deter- mined in the parents, and fetal examination would be indicated if there is already one chance in four that the fetus may be diseased. While the elimination of fetuses having this serious genetic disease May appear to be a negative approach, this procedure should be weighed against the assurance that can be given parents of being able to nurture a child free from disease on future attempts. Eventu- ally, a better understanding of the biochemistry of cystic fibrosis may lead to methods of treatment so effective that the disease would no longer be the serious burden to the young child that it is today. In many respects, mongolism, or Down’s syndrome, is more seri- ous than cystic fibrosis because of its severe mental retardation. Prenatal examination can reveal the extra chromosome that causes the condition. Down’s syndrome occurs in one of about 600 births, © but certain individuals have a chromosome pattern that predisposes them to a much higher frequency of afflicted progeny. For such mothers, and mothers with pregnancies at advanced ages, a prenatal examination of feta! cells is especially indicated. Paradoxically, additional conceptions undertaken to compensate for an eliminated fetus will tend to increase the frequency of the deleterious gene in the population. For example, the child with cystic fibrosis was, until recently, not likely to survive until repro- ductive age and, therefore, did not contribute to the gene pool of the following generation. Also, the diseased child tended to dis- place a potential sibling whose odds are two in three of being a Carrier for the gene and who would eventually contribute to the gene pool. If, however, our objective in this kind of medicine is to alleviate unnecessary human distress, then we should focus our aitention on the reduction of the disease, rather than on the elimina- tion of the gene for it. In spite of the obvious natural selection against it, the gene’s very capacity to survive in the human popula- tion indicates that it might also carry some still unexplained and even beneficial function in human fitness. or Selective breeding Another characteristic (one hesitates to call it a disease) that can be diagnosed by prenatal examination is the sex of the fetus. Im- proved determination of fetal sex at an early age, and the develop- ment of drugs to induce a voluntary abortion that is essentially indistinguishable from induced menstruation may make individual control of the sex of the offspring technically plausible. The use of abortion for this purpose, however, would probably be repugnant to most people. If there are biases favoring one or the other sex, we should, perhaps, be giving more attention to rectifying a social - order that fosters such discrimination. Germinal choice, which is another approach to selective breeding, has been advocated strongly by Julian Huxley and the late Her- mann J. Muller. Their scheme would provide for the banking of sperm from preferred men in cold storage for later voluntary use in artificial insemination. Real problems arise, of course, in the identification of preferred males, even some years posthumously, and in the social environment in which the qualities of one versus another potential sire are publicly touted. However bizarre these schemes for selective breeding may ap- pear, the present world does exhibit a wide disparity in the number of offspring produced by different parents. In some sense, our other social policies establish the pattern for these discrepancies. Yet, we know too little of human genetics to sustain an informed criti- cism (or approval!) of that pattern. It is much more difficult not to be alarmed at some examples of negative family planning in relation to parents’ ability to provide each child with the parental care that should be his birthright. On the other hand, we have still to devise compulsory schemes that can discourage overbreeding where it de- means a child’s rights without at the same time creating an unac- ceptable invasion of the personal freedoms of the parents. Experiments in genetic intervention p Let us now consider some of the more speculative proposals for genetic intervention that are founded on experiments with laboratory animals and plants. It is not easy, however, to set clear boundaries for the subject of genetic intervention. Since one could postulate that the right set of genes could forestall the possibility of a disease - developing in a person, any disease can then be said to have a genetic aspect. Preventive measures, such as the Sabin vaccine for polio, can be regarded as an artificial replacement of the human genes that are unequal to this one of life’s challenges. We do not know, however, whether any living human beings already contain genetic factors for resistance to polio virus. If they did, the com- . parison of resistant and sensitive individuals would put the genetic ' aspect of this kind of medicine into sharper focus. The same point can be made even more vividly by considering the global disease called mainutrition, which is usually regarded as a dietary insufficiency stemming from a lack of appropriate amino acids in the available food. But, because no known human beings have the necessary built-in genes to accomplish the internal syn- thesis of the required amino acids and vitamins, mainutrition can also be regarded as a pan-human genetic defect. By contrast, most plant species and many microorganisms are well endowed with the necessary genes for the biosynthesis of these materials. It is not inconceivable that some humans already possess those genes needed for effective internal synthesis of amino acids, This idea, in fact, now appears somewhat less fanciful than it did with the recent discovery that, among the world’s adult population, prob- ably only Caucasians usually have the genes needed for the forma- tion of lactase, an enzyme jor the digestion of milk sugar. On the other hand, many samples of Negroes and of Orientals tested as adults lacked this capacity and tended to be intolerant of milk. (See Year in Review: FOOD AND NUTRITION.) One conceivable approach to solving the problem of malnutri- tion would be the attempt to find and selectively breed these in- dividuals whose genetic endowment may possibly enable internal synthesis of amino acids. Or we may solve this genetic deficit by producing proper food and distributing it to those who need it, thus accomplishing the same purposes as selective breeding. It is clear that the growth of the human brain is retarded by either maternal malnutrition or malnutrition of the newborn, or both (see Feature Article: WHEN YOUNG CHILDREN GO HUNGRY: EFFECTS ON LEARNING AND BEHAVIOR), It is also sad to have to report that malnutrition is practiced on a large scale as a central process in the world political system. One does not have to grow babies in bottles, as Aldous Huxley envisaged in Brave New World, in order to achieve & separation of human capacities into alphas and gammas. We can merely contrive to feed some mothers and deny others, The brain, in its growth, must be subject to some exolicit regula- tion from external stimuli. This is an urgent item on the humanicist's agenda. We necd powerful tools to deal, on the one nand, with ob- vious defects that cry out to be corrected and, on the other, with the possible enhancement of human intellectual ability. The closest paraliel to this in present practice is the care that physicians take to be sure that pregnant mothers do not suffer from thyroid deficiency. Genetics and transplants Another approach to the modification of an establisned genetic makeup is the transplantation of the tissue or organ from another individual. When the indication for such a transplant is a failing heart or kidney, obviously the operation is not a compensation for a genetic defect. The message is clearer, however, when the in- dication is a metabolically insufficient Dancreas—-say diabetes, though the primary lesion may be elsewhere—or a congenital de- ficiency in some other endocrine gland. Tissue transplantation is sti s€riously impeded by two factors: the phenomenon of tissue rejection based on genetic incompatibility of different individuals, and the serious difficulty of obtaining viable organs for transplant. Fundamenial genetic studies on the determina- tion of the protein structure of antibodies and of tissue antigens may be expected to eliminate the first obstacle. As for organ supply, a thorough understanding of tissue rejection may make it possible to use animal organs for transpiant purposes. (See 1969 Britannica Yearbook of Science and the Future, Feature Article: NEW PARTS FOR OLD: THE LATEST MEDICAL ADVENTURE.) One approach that would ailow the use of animal organs would be the early inoculation of infants wiih purified pooled antigens representing the tissue specificities of potential future organ donors. Transplantation, in the sense of mixing cells of different origin into One crganism, can be done experimentatly at very early staces of embryological development, Alrcady, as many as four different mouse eggs, representing eight difierent parenis, have been fused to form a single embryo that matured into a single adult mouse. This procedure has great theoretical inierest because of its DO- tentiality for incorporating complementary advantages from a variety of different parental strains. Experiments with inicrcorganisms Except for a calculated choice of parentage, intelligent design plays a limited role in controlling the genetic makeup of an individual. In microorganisms, however, it is now possible to introduce specific new genetic information in a much more controlled fashion. But such experiments still have considerable random components, and usually it is not possible to instruct one particular cell to adopt a specific new genotype. Instead, a large number of cells are exposed to DNA that has been contrived to have the desired characteristics. One out of the many cells may incorporate the foreign DNA and with it some new characteristic. The occasional celi that responds in the appropriate fashion can then be separated from the other cells. The great force of recent work in molecular biology stems from the use of relatively simple experimental materials, such as viruses and bacteria. The direct manipulation of individual genes within the chromosomes in cells of higher organisms, however, presents formi- dable and possibly insuperable technical difficulties. Nevertheless, we can foresee the use of viruses to mediate the transmission of Specific genetic information. This process of viral transduction was first described in 1954 by Norton D. Zinder and Joshua Lederberg for bacteria of the Salmonella group. Contemporary work with ‘animal viruses by a number of other workers now strongly Suggests that these viruses may also be capa- ble of introducing genetic information in the cells that they infect. For example, the SV-40 Virus of monkeys, which as far as is known is harmless in man, leaves a number of copies of its DNA sequences in the chromosomes of cells infected in tissue culture. This suggests that viral DNA can be engineered and that synthetic viruses can be used for the modification of genetic defects. For example, it should soon be technically feasible to attach the genetic DNA that codes _ for the enzyme phenylalanine hydroxylase, which functions in the liver of normal men and animals, to the DNA of SV-40 virus, The inoculation of an infant with such a hybrid virus would be expected to alleviate the disease phenylketonuria. Man has, in fact, been practicing a similar form of genetic engi- neéring for quite some time. When Edward Jenner discovered the vaccination against smallpox, he introduced the use of a variant virus to compensate for a “genetic defect” shared by all mankind; namely, our inherent sluggishness in producing antibodies against the smallpox virus. The projected design for the use cf more care- fully engineered viruses to generate specific enzymes shows an obvious parailel to this long-established medical procedure. This approach to genetic engineering also has the advantage that, in all likelinood, the genetic information carried by such viruses is not incorporated in the sex cells for transmission to the next gen- eration. This is a purely empirical observation: to be sure of keeping future options open, this limitation of virogenetic effect to somatic tissues must be carefully verified in every case. At this writing, only one important technical difficulty remains, that of attaching specific segments of DNA from totally unrelated sources. However, enzymes discovered in 1968 for rejoining DNA molecules broken in just one strand are already being used as essential reagents in research. The theoretical possibility of virogenic attachment to chromosomes and propagation to further generations cannot be completely deter- mined without empirical study. If we do not keep a vigilant lockout on the effects of viruses—whether used for vaccination against disease, for genetic repair, or as infectious agents in our environ- ment—we may be in for some unpleasant surprises. Because the use of viruses for vaccination purposes has not been generally as- sociated with the alarms of ‘genetic engineering,” these agents do not receive the close attention they deserve in view of their bi- ological potentialities. At the very least, viruses used for vaccination should be chemically purified and identified as having only the one desired species of DNA or RNA (ribonucleic acid). This standard has not yet been adopted by the pharrnaceutical industry, nor has it been included in the regulations enforced by governments. The extraordinary specificity of pairing by the two strands of a DNA molecule has opened the way for studying biological specificity, mainly by molecular hybridization. The specific reagent in these ex- periments is a solution of DNA single strands prepared from refer- ence material. For some purposes, this DNA may be incorporated into a culture medium of solid agar or attached to the surface of filter membranes. When exactly complementary strands of DNA, or sometimes of RNA, are added, conventional double-stranded DNA structures will be re-formed and can be detected by a variety of different methods. Some of these methods are so sensitive that it may be possible to discern even single nucleotide differences be- tween a reference and an unknown in a sample. These procedures will, undoubtedly, be instrumental for the isolation of specific-gene DNA, an objective which has already been achieved to a limited extent, Molecular hybridization also furnishes a method of distin- guishing from each other the messenger-RNAs produced by different cells. Vegetative propagation Other advances in cell biology have opened up some additional technical possibilities for the evasion of genetic scrambling that now invariably accompanies sexual reproduction. The propagation of new plants from cuttings is a familiar experience in horticulture. In lower animals such as earthworms, vegetative reproduction is a common occurrence: missing organs can regenerate spontaneously in smail fragments cut from the previous individual. One might speculate that deeper insights into the mechanisms of this embryo- logical development could lead to similar phenomena, even in man, but these are remote prospects indeed! An alternative approach is offered by experiments in frogs, in which the existing nucleus of a fertilized egg was displaced and the egg renucleated with a nucleus from a tissue cell of a mature frog. The purpose of these experiments was to determine whether tissue differentiation was invariably associated with a permanent loss of developmental functions in the cell nucleus. Apparently this is not always true, for some nuclei of adult tissue cells are capable of supporting the total development of a new frog from a renucleated egg. From a genetic point of view, however, the new frog was vegeta- tively propagated from the mature tissue because it carries exactly the same set of genetic information. Groups of individuals derived by vegetative propagation and having identical genetic constitutions are called “clones.” The pros- pect of producing genetically homogeneous groups of individuals presents some interesting issues; in addition, it is a way of propagat- ing a genotype already tested in one generation for further trial in a second. We already have a foretaste of the properties of a clone in the behavior of identical twins. Clonal propagation would afford an otherwise unavailable oppor- tunity for certain humanic experiments, in the same sense that efforts to optimize a child's education are experiments. Without such tests it is unlikely that we will ever be able to know the extent to which the performance of acknowledged geniuses or athletic stars are manifestations of unusual genetic endewment. The technical limitation to human cloning is mainly the much © smaller size of mammalian eggs when compared with the egg of a frog, but, almost certainly, this is not an insuperable difficulty. There may be, however, other obstacles based on differences in the biology ef the frog egg and that of the human that are not yet known, Within the last few years, it has boen discovered that tissue cells can be made to fuse with cne another in the presance of certain virus-derived particles. These cells thus form “vegetative hybrids” that can originate from such widely cistinct species as fish and human. The technique has already become quite important in the analysis of the acne netic fu netions carried by different hurnan chromo- somes, which can be tested for their ability io make up for known defects in other animal cells. Vegéiative hybridizaticn and the use of the hybrid cells to re- nucleate an egg cpen the door to another form of genetic engi- ning some or many chromo- a neering—hybrid plants or animals cont somes from distant species. Cron improvement is the most obvious area for applying this technique. In fact, many Soviet workers have nade far-reaching claims far the efficacy of graft-hybricdization in plant improvement, but most of these claims defy reproducibility and credibilily. Perhans for this reason the whole subject has been virtually ignored by Niestern geneticists, who may thereby have missed some karnel of useful innovation. The iilure of censtice ¢ Fined When we approach functions as compiex as human inteliaences and sympathy, we must be quite humble about our capacity to unravel ihe components of heredity and environment. Certainly, there fs no gene that can ensure the ideal development of e child’s brain with- out reference to iender care and Inspired teaching. The paths to inteligence can be devialed at many poinis—for example, the child born deaf was for all practical purposes an idiot until we learned ach him, Thess consicerations may be io sharpen the special technicues needed to is sugeest that the main role of genetic science percepticns of how to engineer the environment for the cotimum development of existing Genetic tyoes. When wa have reached some mastery of this challenge, we can more reasenably advecate the Am mo extension of genetic engincering beyond the repair of the most ob- vious and urgent forms of genetic defect. CONCLUSLON Humanics, tie understanding of human nature, is rightly viewed as the. cepstone of Western culture. Scientific insight is, how fever, a challenge to traditiona! thought and authority in at least two ways. It amplifies the power for good or harm that msn can inflict on cne another, when we are already on the brink of failure to contain mas- sive aggression, Pernans even more embarrassingly, it reveals exist- ing flaws in the providence and justice of our social institutions— like the world arrangements that leave so many human beings underfed and uneducated, Viany thoughtful critics have questioned whether we are sociaily and morally prepared to cope with such newly emerging powers as genetic engineering. Some go so far as to advacate explicit restraints on technological development in this field, a plea that Is r nai trans- lated into difficence about financial support for basic biolcgical re- search. The straw man has even been erected that pictures scientists (out which ones?} as dernanding that we put into practice everything that Is technologically possible, without recard to the human con- sequences, Such absurdities should not require discussion, but insofar as they do, they have a positive answer. The consequences of ignorance are no less frightening, perhaps more unpredictable than those of scientific understanding. When we contemplate iarge-scale tech- nological applications in any sphere, we need a wide range of sci- entific Knowledge to analyze their consequences. Restraints on re- search in genetic science miaht restrain sophisticated cenetic engineering, but they will make even more plausible the crude efforts of those who advocate the legalized involuntary sterilization of the “unfit” and deprive us of many urgently needed-advances in med- icine and jn agriculture, Sharply limited military research would never have uncovered the genetic hazards of radioactive fallout. The euphenic point of view may upse: Sorne people who do not know how to handle the respon- sibility of choice for the quality of their offspring, but our present uninformed choices, tike those that lead to global malnutrition and menial rétardadcn for millions ef infants, are also a policy. Man may have tived in a paradise of submissive ignorance before he ate from the tree of knowledge, but human civilization began just then and there is no return. , This is nct to shrug off the perversion of science. Brute force is the overriding instrument of authority, but the most totalitarian gov- ernments will exoloit more subtle weapons to secure the peaceful cooperation of their subjects. The “control of the mind” by chem- icals is the usual cliché one thinks of here, but Aldous Huxley him- self pointed out that the scientific techniques portrayed in Brave Jew World were intended as a parody of existing institutions. Is it jess intrusive on a human personality to indoctrinate a child in a given set of religious’ beliefs than it would be to “program” his genes? (Usually, the answer is “yes’'—if the religion is the right one.) But dictators will not stop at propaganda; they will use genetic engineering too, if they have the wit and if they stay in power long enough. The only answer is to strengihen our democratic institutions, of which public education to make informed critical judgrnent is the most crucial. We should also minimize the intrusion of government in any aspect of individual reproductive policy. It is incredible to think that, until recently, many states had laws that interfered with the dissemination cf information about family planning. It is equally incredible that most states still interfere with the private decision of a mother to abort an unwanted pregnancy. The self-awareness that characterizes man is part of his unique capacity for cultural evolution. During the past 190,000 years, this has compieicly cvertaken his biological evolution. Biological change during this period is not only mucn less importani than the cultural, but is itself deeply influenced by self-awareness, as illustrated by the rapid differentiation of the races with respect to obvious features as opposed to ine deeper elements of humanity. Self-ewareness may also impede substantive biological change unless we can iearn to assimilate a view of the human future that allows for variety, ex- perimentation, and change. What is quite new is that we are now scientifically aware of evolution and must take on the burden of conscious choice about its future directions. The most important ethical inference from the fact of human evolution is that we are still perfectible, It is one of the least debata- ble of human purposes that our posterity should be wiser than we are, and above all for deciding the direction of the species. This principle puts a high premium on preserving the flexibility of de- cision for future generations, to make the fawest irreversible de- cisions. It is arguable whether evolutionary commitments are less reversible than cultural ones, but we would still prefer euphenic and somatic mcedifications io those that committed the whole species to anew genotype. On the other hand, we should not confuse global shifts (jor which war is already more pertinent than eugenics) with isolated experiments in genetic engineering, any more than we would confuse global indoctrination with efforts at educational ex- perimentation. See also Year in Review: MOLECULAR BIOLOGY. FOR ADDITIONAL READING: Dobzhansky, T., Mankind Evolving (Yale University Press, 1984). Haynes, R. H., and Hanawalt, P. C. (eds.), “The Molecular Basis of Life,” Readings from the Scientific American (Freeman, 1988), Lederberg, Joshua, “Experimental Genetics and Human Evolu- tion,” Beyond Left and Right: Radical Thought tor Our Times, ed. by Richard Kostelanetz (Morrow, 1968). Lerner, |. M., Heredity, Evolution and Society (Freeman, 1968). Piatt, J. R., “The New Biology and the Shaping of the Future,” The Great Ideas Today 1968 (Encyclopeedia Britannica, 1968). Sonneborn, T. M. (ed.), The Control of Human Heredity and Evolu- lion (Macmillan, 1965). Taylor, G. R., The Biological Time-Bomb (World, 1868). io bgsenteld, A., The Second Genesis (Prentice-Hall, AUDI VISUAL MATERIALS FROM ENCYCLOPAEDIA BRITANNICA EDUCATIONAL CORPORATION: Films: DNA: Molecule of Heredity; Gene Action; Laws of Heredity.