GENETIC OF MAN by A. H. Sturtevant

Man is, irl many ways, very unsuitable as an ob- standing of the genetic components of some dis- ject for the study of . Families are too small eases and have also been occasionally helpful in for dependable determination of ratios, desired test diagnosis. Mainly for these reasons, many medical matings cannot be made, and study of more than schools now have departments of medical genetics, a very few generations for 'my particular purpose is and several standard books on the subject have bee11 not often possible, The social implications of human published. The clear-cut cases have also been of im- genetics are so great, however, that the subject must portance in physical anthropology. be investigated; and there are some real advantages The more obvious arid familiar human differ- in the material. For no other organism do we have ences, such as stat~~re,hair form and color, eye color, such detailed and extensive information on anato- skin color, right- vs. left-handedness, or fingerprint my, develop~nent,biochemistry, physiology, pa- patterns, although obvio~~slyinherited, are difficult thology, , and population statistics. to analyze. In other mamrnals, hair color and eye A large list of more or less clear-cut Mendelian color are among the best understood of the inherited differences in marl has gradually been built up, characteristics, but in man there are so rnany inter- largely concerned with relatively rare defects or mediates that analysis is difficult. Red hair and blue with less obvious biochemical variations such as eyes are often listed as due to recessive , which blood groups, hemoglobin types, or variations in they may be, but in both cases classification is often urine composition. uncertain, and if one depends on the usual popular These cases have been important in the under- descriptions, there will be contradictory observa- tions. "The Genetics of Man" is adapted from A. H. Sturteoant's book, A , publ~~dlast month by Harper &- Row. Even more difficult to analyze are mental prop- 14 Engineering arid Science erties, a11d ol~viouslythese are the human charac- family would have had no chance of realizing those teristics that are of the greatest interest and impor- potentialities-but the book does not bring out this tance to society. At the sensory level, there are well- point. established Mendelian differences that must have Similar views have been expressed since 1900 by indirect effects on behavior-such things as taste other biologists-including some who were more sensitivity, night blindness, or color blindness. Since sophisticated than Davenport. Two examples fol- I am partially color blind, 1 am acutely aware of low: some of the effects of my relative insensitivity to Bateson (1912, "Biological Fact and the Struc- redness. Sunsets or desert colors are clearly lesser ture of Society," Herbert Spencer lecture, Oxford) : sources of esthetic satisfaction to me than they are to most people, and I am so unaware of the redness caused by inflammation that I could never have been a successful practicing physician. At the other extreme, there are more or less clear- Alfred H. Sturtevant ly established Mendelian cases that involve serious is a distinguished elder statesman of biology who mental conditions-such things as Huntington's is recognized as a pioneer in the study of genetics. His career l~egannearly 60 years ago at Columbia chorea and phenylketonuria. University where he was a student of Thomas Hunt It is the range between these extremes that is both Morgan. Together with Morgan and several other the most interesting and the most diEcult to ana- brilliant colleagues (including Hermann Muller and Calvin Bridges), he studied the genetics of the fruit lyze. One of the first attempts was made by Galton. a " fly Drosophild in small, crowded laboratory that He was responsible for the expression nature vs. came to be called the "Fly Room." There, modem nurture" in the determination of human character- genetics, which had its basis in Mendel's unheralded work 50 years before, fi~iallycane of age. Results of istics, although it is probable that he assumed his the early work done at Columbia were published in readers would recognize Shakespeare as the source 1915 in a monumental book by Morgan, Muller, of the expression (in The Tempest, concerning Bridges, and Sturtevant, The Mechanism of Men- what led to Caliban's character). Galton (1869) delian . Aiter receiving his PIID from Columbia in 1914, collected a series of pedigrees showing the concen- Dr. Sturtevant remained in the FIy Room as a Carne- tration of particular kinds of exceptional achieve- gie Institute research fellow. His work through the ments in particular families, such as milsicians in the 20s included discovery that a 's action depends on what genes are next to it in the -the Bach family. He minimized the effect of family tra- phenomenon of position effect. He studied sex deter- dition and concluded that the results were primarily mination, and sexuality and sexual selection. He due to biological inheritance, despite one case that worked out the non-random segregation of the tiny, he pointed out but did not emphasize. In the Roman fourth chromosome in Drosophila. He drew new con- clusions about evolution from studies of inversions of family of the Scjpios there was an extraordinary . He investigated the comparative ge- concentration of generals and orators, but one of netics of Drosophila and found the same gene show- them ( Scipio Aemilianus 1 "was not of Scipio blood" ing up in different species. He recognized that a gene can exist in multiple alternative forms. He worked on but was an adopted son, suggesting (though not to the bizarre aspects of evolution in the social insects, Galton) the importance of family tradition rather where selection operates riot so much on what the than genetic composition. individual is, as on the groups into which his progeny fall. He made important contributions to understand- This same approach was later followed by Daven- ing the sterility of liybrids. And he has delved into port (Heredity in Relation to Eugenics, 1911). Here the genetics of organisms having more than two sets there is a description of the Tuttle-Edwards family of chromosomes in his studies of ins. of New Ijaven, from whom descended two presi- In the course of this work he came, with Morgan, to Cdtech in 1928 to take his place in the newly or- dents and one \/ice president of the , gdn~zeddivision of biology and for five years after six college presidents, and other notables: and of the Morgan's retirement in 1941 was a member of the Lees of ?7irginia, who ran to generals and political team of four administering the division. In 1951 he was named the first Professor figures. There follow acco~intsof the Jukes and of Biology at Caltech. In 1962 he retired, but still Kallikak families, with their dreary procession of continues his research activities on the campus. prostit~ites,thieves, drunkards, and paupers, Here In addition to extensive participation in profession- al organizations, Dr. Sturtevant has received many again was little or no recognition of the overwhelm- honors, including the Kimber Genetics Award from ing importance of family environment and of the the National Academy of Sciences in 1957 "for his resulting opportur~itiesor lack of opportunities in distinguished career as discoverer and interpreter of these exan~ples-Surely Davenport must have ~11- fundamental genetic phenomena"; and the Carty Medal of the National Academy of Sciences in 1965 derstood that a potential college president, or mem- "for noteworthy and distinguished achievement." ber of the Virginia legislature, born into a Jukes December 1965 Much of the discussion about nature versus rturtzlr~/Z~IS beer1 OH,t?te err~otional level, because ~~n~~mbiguuusobjective evidence is so difficult to get.

"How hard it is to realize the polymorphism of As it happens, the ~msteffective approach to this man! Think of the varieties which the word denotes, question was initiated 1)~Galton ( 1883, lrtquiries merely in its application to one small society such into Hurriarz Fczrz~lty) . In 2 series of stuclies on pairs as ours, and of the natural genetic distinctions of twins, he recogr~izedthat they were of two kinds, which differentiate us into types and strains - acro- "similar" and "dissimilar,'*ancl concl~~dedthat these bats, actors, artists, clergy, farmers, Iaho~irers,law- arose, respectively? from a single fertilized egg and yers, mechanics, musicians, poets, sailors, men of from two ir1cIe~endent1yfertilized eggs. Thiq con- science, servants, soldiers, and tradesmen. Think of clusiori has since been confir~nedby ekhrjologiial the diversity of their experience of life. How Iew of evidence and by extensive genetic- stt~dies;the two these could have changed parts with each other. types are now ~~suallyreferred to as rnc~riozygotic Many of these types are, even in present conditions, (or identical ) and dizygotic (or fraternal ) . Galton almost differentiated into distinct strains . . . 1 never saw that they offered an opportunity to test the rel- cease to marvel that the more divergent castes of ative importance of nature and nurt~we,since the civilized humanity are capable of interbreeding and rnonozygotics should be alike in genetic makeup, of producing fertile offspring from their crosses. whereas the dizygotics should be no rnore alike than Nothing but this paradoxical fact prevents us from ordinary brothers and sisters. He carried out a few regarding many classes even of Englishmen as clis- tests on mental properties and cor~cl~~dedthat the tinct species in the full sense of the term.'' moric~zygc)ticswere in fact more alike in behavioral Darlington ( 1953, The Facts of Life ) : "In Eng- attributes. land, for example, it is not lack of research which The next step was taken by Muller (1925). He limits food production but the genetic unfitness of found a pair of monozygotic twins who had been a large part of the tenant farmers, the legally se- separated in early life and brought up in different cured occupiers who are organized to keep better families. He gave them a series of psychological men off the land." tests, and foilnd them to be quite similar, This Such extreme views have not gone unchallenged. method was greatly extended by Newrnan, Free- Especially among anthropologists (largely under man, and Holzinger ( 1937). They found a consider- the infl~ienceof Boas) and among psychologists able series (20) of such separated monozygotics there has been a strong tendency to minimize the and, as controls, carried out the same tests 011 effects of genetic composition on human behavior. a series of monozygotics, and also of dizygotics, The most extreme statement of this positior~that 1 reared together. The book makes fascinating read- know is by Watson (1925, Beltaciorisvr~):"In the ing - especially the detailed case histories - but the case of man, all healthy individuals . . . start out authors admitted to disappointnient at the incon- equal. Quite similar words appear in our far-famed clusiveness of the results. Later series of such stud- Declaration of Independence. The signers of that ies have also heen rather disappointing, although document were nearer right than one might expect, there can be no question of their importance. considering their dense ignorance of psy~hology. Among the difficulties encountered may be men- They would have been strictly accurate had the tioned the ~~ncertaintyas to just what the psycho- clause 'at birth' been inserted after the word equal." logical tests are measuring, the varying ages at Much of the discussion of this question has been which the separations took place in the different on the emotional level, because unambiguc)us ob- pairs, the inacci~racyof the underlying tacit as- jective evidence is so difficult to get. By and large, sumption that twins reared together are exposed to the extreme proponents of genetic determination identical environmental effects, and the circum- have tended to be political conservatives with their stances that the separated twins were usualIy reared views ultimately rooted in the caste system of feu- in rather similar families (never was one brought dalism, while the extreme advocates of environ- up as a Lee and his twin as a Jukes). Nevertheless, mental control have tended to represent a political these studies have convinced most unbiased stu- philosophy derived more from the egalitarianism dents that there is an appreciable inherited com- of the French Revolution. contintied on page 20 16 Engineering and Scier~ce The Genetics of Man . . . continued ponent in the determination of human mental In the early days of Mendelism, there were many differences. people who felt that this objective could be rather The difficulties of objective study of mental dif- simply achieved, but with increased knowledge this ferences reach their maximum in the case of racial hope has been somewhat dimmed. The easiest class differences. If it be admitted that there are in- of defects to eliminate should be the dominant, but herited individual difference~, then on general it has turned out that the wore serious of these are grounds one must conclude that there are statistical apt not to appear until the normal reproductive age differences between races. If one is inclined to look has largely passed (the typical example here is upon individual mental differences as largely ge- Huntington's chorea). Presumably those that ap- netic in origin, he then is likely to consider the ob- pear earlier in life have, for the most part, been served (or imagined) cultural differences between eliminated by natural selection. Any appreciable the races as being genetically determined and to decrease in the incidence of recessive defects would conclude that some races (inevitably including the depend on the identification of heterozygous car- one to which he belongs ) are inherently superior. riers - which is not usually possible. There has also The extreme examples of this attitude have not come to be a growing realization that, in some cases, usually been scientifically trained; the terrible ex- heterozygosis for a particular gene may (at least ample is Hitler, of course, but he was preceded by under certain conditions ) confer an advantage even many pseudo-scientific writers ( such as Gobineau, when homozygosis is very disadvantageous. The Houston Chamberlain, and Madison Grant), most best-known example here is sickle-cell anemia in of whom would have been horrified by Hitler's man. Homozygosis tor this gene causes the serious methods. There have, however, been biologists with defect from which the name is derived; but it was some background in genetics who have leaned in shown by Allison ( 1954 ) that heterozygosis for it this direction. Since racism is a dirty word, it is per- confers considerable resistance to malaria and so is haps kinder (and certainly more agreeable to the of selective advantage where malaria is prevalent. writer) not to name them. It remains uncertain how frequent this type ofrela- tion is, but the possibility suggests that caution be Can genetics be controlled? exercised in any attempt to eliminate undesirable recessives. A further point has been emphasized by Galton was one of the first to suggest the possibil- Haldane. namely, that a recessive which interferes ity of the genetic improvement of human popula- with the fertility of the individual must be retained tions; he introduced the word eugenics to designate in the population largely by recurrent and this field of study and planning. There are two ap- therefore cannot be eliminated by artificial selec- proaches here, which have been described as "nega- tion, although its frequency may be reduced. tive" and "positive." The first proposes to decrease or eliminate the more extreme inherited defects - Who sets the goals? physical and mental - and the second proposes to increase the number of better individuals, and Positive eugenics seems even more difficult, for thereby to make possible the production of still several reasons. It is evident that animal breeders better ones. Both approaches, especially the positive have, by selection from mixed populations, pro- one, are based on the obvious success of animal and duced many reasonably uniform breeds, possessing plant breeders in improving the populations with desired characteristics and including many individ- which they work. uals more extreme in these respects than any found It is estimated that something like 4 percent of in the original population. There is no reason to human infants have tangible defects that can be doubt that similar results could be obtained with detected in infancy - some of them very serious human populations. But there is a whole series and others much less so, and some of them remedi- of obvious difficulties - of which the greatest is: able and others not. It is also estimated that perhaps Who sets the goals? Who functions as the animal about half of these are largely genetic in origin. If breeders have, in determining the basis of selection? it were possible to eliminate these by preventing Obviously no sane person would want a Hitler to their birth, this would obviously be a great advan- have this power and responsibility, and most of us tage to society, in economic and, especially, in hu- would agree with ates son in mistrusting even a manitarian terms. committee of Shakespeares. Engineering and Science