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Radiation, Genes, andMan. By Bruce Wallace and Th. Dobzhansky. New York. Henry Holt & Co., 1959. Pp. xü+205. $3.50. Popular books on this topic fall into two classes: diose which are obviously biased, which is not to say that they are always written in bad faith; and diose which are reasonably honest but in die interests ofsimplification leave out "details" which would not be left out in a paper to be printed in a scientific periodical. Wallace and Dobzhansky's book falls into the second class. I personally agree widi most of their guesses—for example, that even after an atomic war die human race would neither become extinct nor degenerate into a collection of monsters, but that, neverdieless, the effects even oftesting fusion bombs are serious enough to warrant stopping such tests. Now let us consider some ofdie omissions. Like almost all American audiors, Wallace and Dobzhansky are rather chancyinreporting workdone outside America. Forexample, in 1935 L. S. Penrose and I first calculated die mutation rates oftwo human genes. We published a shortjoint paper to avoid possible squabbles about priority. Neverdieless, on page 37 my name is mentioned in this connection and Penrose's is not. Much more serious is the omission on page 149. The authors quote the work ofNeel and Laurence on children ofpeople heavily irradiated at HiroshimaandNagasaki, and they also note the work of Macht, Laurence, and Crow on die children of American radiologists. Both series showed a slight increase in abortions and stillbirths, and one ofthem an increase in malformations —but all were slight. They did not mention the work ofLejeune and Turpin on the children of French men and women whose gonads had been heavily irradiated. The irradiated mothers bore an excess ofdaughters, as was to be expected ifrecessive ledials were induced in their X-chromosomes. The irradiated fathers begot an excess of sons, as would be expected if dominant lethals were induced in their X-chromosomes. The figures suggest a radier higher mutation rate dian was calculated on page 133. Since the book was written, Lejeune has discovered diatmongoloid imbecilesare trisomie, thus opening a new chapter in human genetics. One cannot neglect Lejeune any longer. An omission which seems to me serious is this. The calculations in chapters 7 and 8 are based on the assumption that marriage is at random as concerns recessive genes; that is to say, that the probability that a heterozygote will marry another heterozygote is simply the frequency of heterozygotes in the population. This is probably nearly true in the United States today, but it was not true of the ancestors of the Americans in the year 1600. Most ofdiem lived in inbred European rural communities. Inbreeding brings recessive genes togedier, and if the homozygote is unfit, it squeezes deleterious recessive genes out ofa populationjust as wringing squeezes water out ofa cloth. When inbreeding is relaxed, much fewer defective homozygotes are born, but the frequency of the genes concerned gradually increases by mutation. Ifdiis argument is correct, the rate at which "spontaneous" harmful recessive mutations appear in man is larger than the authors believe, and dieir calculations require revision. The diird omission is as follows. In calculating the bad effects ofmutation, spontaneous or induced, die audiors assume diat diere is no way ofpreventing die marriages of like heterozygotes. But in the last ten years mediods have been devised, mainly in the United States, for detecting heterozygotes for a variety of harmful récessives, including phenyl567 ketonuria, galactosemia, several kinds ofclotting defect, acatalasemia, and most of the abnormal hemoglobins. In another generation I hope diat most people will be examined at puberty, told for what harmful recessive genes diey are heterozygous, and warned against marrying similar heterozygotes. If2 per cent ofall babies are homozygous for a harmful recessive, which I think is an exaggeration, 8 per cent ofmarriages will be contraindicated . Ifit is concluded diat X-rays—which are at present die main source ofgenetic damage—bomb tests, and peaceful uses ofatomic energy are increasing human mutation rates, the resulting scare may lead not only to increased medical research but to free and compulsory tests for heterozygosis. If so, die final effect of increased mutation on the human species...


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