Science in Christian Perspective

CHROMOSOMES AND HUMAN BEHAVIOR
V. ELVING ANDERSON
Dight Institute for Human Genetics 
University of Minnesota Minneapolis, Minnesota

From: JASA 21 (June 19369): 48-49.

An adequate technique for studying human chromosomes was first reported in 1956. Three years later the presence of an extra chromosome (trisomy) was discovered in cases of Down's syndrome (mongolism). Since then human cytogenetics has developed into an important research and clinical tool.¹

EFFECTS AND INCIDENCE

Some of the chromosomal aberrations result in severe congenital malformations, mental retardation, and reduced life span. Variations in the number of sex chromosomes may cause infertility, specific malformations, and some intellectual impairment. At least one per cent of newborn children have an abnormal chromosome constitution of some type.² The incidence of certain abnormal sex chromosome patterns is approximately
as follows: 

XO  (Turner's syndrome) 
XXY  (Khnefelter's syndrome) 20 per 10,000 newborn males 
XXYY 1 per 10,000 newborn males
XYY 3-5 per 10,000 newborn males

The first case of an XYY pattern was reported in 1962, and a dozen more were added in the next three years. Meanwhile studies of selected populations were carried out. Casey et al.² found 21 out of 942 men in two English special hospitals for dangerous, violent, or criminal patients of subnormal intelligence to be chromatin-positive (having two X chromosomes). Of these 7 had an XXYY pattern. The unusually high frequency of two Ys suggested a possible relationship with the reason for institutionalization.

Following this lead, Jacobs et al.⁴ studied 342 men in a similar hospital in Scotland, and found 16 with chromosome anomalies (9 with XYY, one XXY, one XXYY, one mosaic XY/XXY/XXXY, and four with problems involving other chromosomes). For the ten men with two Y chromosomes the mean height was 72 inches, as compared with a mean of 67 inches for other men tested. Of the nine XYY males, seven were considered to be subnormal in IQ. Eight were cooperative in the test situation, while one was sullen, solitary, and suspicions. There was no history of excessive alcoholism. They gave the general impression of lack of emotion, casualness, and absence of guilt. The most common crimes were theft and housebreaking.

In the same XYY subjects Price and Whatmore⁵ reported no physical abnormality or problem in sex development. The mean age at first conviction was 13 years as compared with 19 years for controls. There appeared to be a limited capacity for affection and an inability to establish normal interpersonal relationships. A more detailed psychological study of 7 of these subjects and 11 matched controls was reported by Hope et al.
Telfer et al.⁷ studied those inmates of four criminal institutions in Pennsylvania who were 71 inches or more in height (a total of 129) and found seven XXY and five XYY. In a Melbourne prison among 34 men 69 inches or taller Wiener et al.⁸ found three XYY and one XYY/XYYY. Thus an unusually high prevalence of a YY pattern has been found in several independent samples of tall men in criminal institutions.

IMPORTANT QUESTIONS

Some important questions must be answered by further research:

1) How common is an XYY pattern among males in the general population? The estimate of 3-5 per 10,000 given above is only a first approximation. It is possible (but not yet certain) that there are many XYY males who are essentially normal in behavior.
2) Assuming that variability in physical features and behavior will be observed, what biochemical or anatomical differences are there between those XYY males who show tendencies toward criminal, anti-social, or aggressive behavior and those who are essentially normal?
3) If a significant proportion of XYY males show behavior problems, what modes of therapy (biochemical or psychological) will aid in ameliorating or preventing the difficulties?
4) Here is an opportunity to define more clearly what is meant by aggressive or antisocial behavior. Social scientists who specialize in such problems can make a significant contribution to their own fields and to human genetics.

BASIC PROBLEMS

These findings also pose some interesting problems for pastors, teachers, and parents:

1) If an XYY effect upon behavior is established, this is only one addition to a growing list of specific genetic conditions affecting human behavior. The Lesch-Nyhan⁹ syndrome is another recently identified trait, involving mental retardation and a bizarre form of self-mutilation. It is no longer possible (if it ever was) to view the "mind" as isolated from the "body."
2) Does this mean that a person is not responsible for his actions? It is difficult to answer this question directly. Society has already accepted the idea that under certain conditions (such as "insanity") an individual cannot he held responsible. The XYY condition would appear to be only one specified extension of this principle.
3) If a baby boy is found to have an XYY chromosome pattern, what should his parents be told? In view of the recent reports in popular magazines on the XYY male, this information may be more threatening to his parents than a diagnosis of severe mental retardation. When more detailed information becomes available about the differences between those with disturbed and with normal behavior, some more precise tests may permit more accurate predictions. Meanwhile, the physician in some cases may decide to withhold the
information, merely stressing the need for frequent check-ups.
4) In other genetic conditions we are finding that some affected individuals develop well without beatment. On this basis, it is reasonable to insist that prognosis, therapy, and education for an XYY male should never he based only on chromosome studies. Other types of individualized assessment are always essential.

REFERENCES

¹Bartalos NI., Barannki, TA. 1967 Medical Crjtogeneties. Baltimore: Williams & WiHkins.
²Cnsirt Brown, VT. 51. 1967. Human Population Cytogenetics. Amsterdam: North-Holland Publishing Co.
°Casoy, M. I).,Se gall, L. J., Street, D. B. K., Blank, C. E.
1966. Sex chromosome abnormalities in two state hospitals for patients requiring special security Nature 209:641
4Jacobs, P. A., Price, W. 11., Court Brown, IV. M., Brittain,
B. P., %vhat:-iore, P. B. 1968. Chromosome studies on men in a Maximum Security Hospital. Ann. Iluns. Genet. 31:339 5Priee, W. H., Whatmore, P. B. 1967. Behavior disorders and
pattern of crime among XYY males identified at a maximum security hospital. Brit. Med. J. 1:533-536
5Hnpe, K., Philip. A. E., Lnughran, J. M. 1967. Psychological
characteristics associated with XYY sex-chromosome complement in a state mental hospital. Brit, J. Psyeldat. 113:495-498
TTelfer, M. A., Baker, D., Clark, C. B., Richardson, C. E. 1967.
Incidence of gross chromosomal errors among tall criminal American males. Science 159: 1249-1250
5Wienor, S., Sutherland, C., Bartholomew, A. A., Hudson, B.
1968. XYY males in a Melbourne prison. Lancet 1:150
ONyhan, William L. 1968. Clinical features of the Lesch-Nyhan
.syndrome. Fed. Proc. 27:1027-1041

*Presented at the Convention of the American Scientific Affiliation at Calvin College, Grand Rapids, Michigan on August 20, 1968.