The Veddahs of Ceylon are probably the most in-and-in bred people that ever existed. Among them, the practice of a man marrying his younger sister did not occur only occasionally; according to Mr. Bailey, it was the proper marriage. Among the Bintenne Veddahs, it may be said to have been, for perhaps two generations or so, extinct, whilst among those of Nilgala, it is at most only disappearing. Mr. Bailey believes that this practice is quite sufficient to account for the short stature as well as the weak and vacant expression of this people. He did not find many traces of insanity, idiocy, and epilepsy—maladies which such marriages, according to a common belief, might be supposed to produce. “But in other respects,” he says, “the injurious effects of this custom would seem to be plainly discernible. The race is rapidly becoming extinct; large families are all but unknown, and longevity is very rare. I have been at some pains to obtain reliable data to elucidate these points. Out of seventy-two Veddahs in Nilgala, fifty were adults, and twenty-two children. In one small sept, or family, there were nine adults and one child; in another, one child and eight adults; and so on. In Bintenne, out of three hundred and eight Veddahs, a hundred and seventy-five were adults and a hundred and thirty-three children. Here the disproportion is not so marked; but in one of the smaller tribes, more isolated than the rest, there were twenty adults, and but four children. The paucity of children, I think, must be ascribed to the degeneracy produced by such close intermarriages, for I have never heard a suspicion of infanticide existing among them. Out of fifty adults in Nilgala, only one appeared to have numbered seventy years, and but eight to have exceeded fifty. In Bintenne, of a hundred and seventy-five adults, two only seemed to have reached their seventieth, and but fourteen to have exceeded their fiftieth year. Such statistics seem to show the practical results of such connections. The Nilgala Veddahs, who still maintain an almost total isolation from other people, are rapidly disappearing. The Veddahs of Bintenne, who have abandoned the pernicious custom which I have described, and still intermarry among themselves, are becoming extinct, though more gradually.”[2001]
With the exception of this case, the closest kind of intermarriage which we have opportunities of studying is that between first cousins. Unfortunately, the observations hitherto made on the subject are far from decisive. Several writers, as M. Périer, Dr. Voisin, and Mr. Huth, believe that there are no injurious results at all from those marriages, unless the parents are afflicted with the same hereditary morbid tendencies,[2002] whilst others, as M. Devay and M. Boudin, express the most alarming opinions as to the bad effects of consanguineous marriages. Such alliances are supposed to bring evils of many different kinds upon a population, as sterility, idiocy, epilepsy, insanity, deaf-muteism, congenital malformations in the offspring, cretinism, albinoism,[2003] &c. But how little the statements of the various writers agree with each other appears, for instance, from the fact that M. Boudin found the proportion of deaf-mutes born in consanguineous marriages, in the Imperial Institution of Deaf-Mutes at Paris, to be 28·35 per cent., whereas, according to Dr. Mitchell, it amounts to 5·17 per cent. in Scotch and English institutions.[2004]
As it is impossible to dwell here upon the investigations of the several writers, of which Mr. Huth has given so complete an account, I shall confine myself to a statement of the general results attained by those investigators who have founded their inquiries on a more trustworthy statistical basis.
Adopting a method different from that of his predecessors, Professor G. H. Darwin has endeavoured first to discover the proportion of consanguineous marriages in the whole population, and then to find out whether the offspring of those marriages exhibit a greater percentage of individuals, defective in one way or another, than the offspring of non-consanguineous marriages. His investigations tend decidedly to invalidate the exaggerated conclusions of many previous writers, but he thinks that “there are nevertheless grounds for asserting that various maladies take an easy hold of the offspring of consanguineous marriages.”[2005] He did not find evidence that the marriage of first cousins had any effect in the production of infertility, deaf-muteism, insanity, or idiocy, but he observed a slightly lowered vitality amongst the offspring of first cousins, and a somewhat higher death-rate than amongst the families of non-consanguineous marriages.[2006] Moreover, the numbers of boating men belonging to the twenty boats at Oxford and thirty at Cambridge, in the first and second division, and those of selected athletes from some schools in England, justified, to some extent, the belief “that offspring of first cousins are deficient physically, whilst at the same time they negative the views of alarmist writers on the subject.”[2007] It is curious that, in spite of such unambiguous statements, Mr. Darwin’s paper has generally been quoted as an evidence of the perfect harmlessness of first cousin marriages.
M. Stieda has found that, in the departments of France, the number of bodily or mentally infirm people increases almost constantly in proportion to the number of consanguineous marriages, as will be seen from the following table:—
| Group. | Number of departments. | Number of consanguineous marriages in each thousand marriages. | Number of infirm people in each thousand inhabitants. |
|---|---|---|---|
| I. | 10 | 5·4 | 2·3 |
| II. | 10 | 8·3 | 2·8 |
| III. | 14 | 9·95 | 3 |
| IV. | 10 | 11·2 | 2·4 |
| V. | 13 | 12·5 | 2·8 |
| VI. | 8 | 13·8 | 3 |
| VII. | 14 | 15·8 | 3·5 |
| VIII. | 10 | 19·2 | 3·25 |
| I.—IV. | 44 | 9·2 | 2·65 |
| V.—VIII. | 45 | 14·8 | 3·1[2008] |
The Danish physician, Dr. Mygge, published in 1879 a book on ‛Marriage between Blood-Relations,’ which unfortunately has received much less attention than it deserves.[2009] Thanks to the trustworthiness of the method, the number of cases considered, and the author’s impartiality, it is probably the most important statistical contribution hitherto issued on this subject. Dr. Mygge found, from the information he received from various parts of Denmark, that in that country, or at least in the parishes of it which came under his observation, there occur, among the children of related persons, comparatively more idiots, lunatics, epileptics, and deaf-mutes than among others. He considers it probable, too, though not proved, that such children die in a higher ratio and are more liable to certain diseases. But, on the other hand, he did not notice any perceptible difference in fertility between consanguineous and crossed marriages.[2010]
In these inquiries, Dr. Mygge followed the method applied by the Norwegian physician Ludvig Dahl twenty years earlier. Through careful investigation of 246 marriages, eighty-five of which were between first cousins and four between still nearer relations, this inquirer was led to the conclusions that consanguineous marriages are somewhat less fertile than crossed marriages; that they produce comparatively many more still-born and sickly children; and that insanity, idiocy, deaf-dumbness, and epilepsy occur about eleven times as often among the offspring of relations, as among the offspring of unrelated parents. But he admitted that the numbers compared were too small to make his conclusions decisive.[2011]
These results are of course to a great extent conjectural. But it is noteworthy that, of all the writers who have discussed the subject, the majority, and certainly not the least able of them, have expressed their belief in marriages between first cousins being more or less unfavourable to the offspring.[2012] And no evidence which can stand the test of scientific investigation has hitherto been adduced against this view.
Some writers have, indeed, cited instances of communities where consanguineous marriages have occurred constantly without any evil effects having appeared. Thus the Pitcairn Island, uninhabited till the year 1790, was at that time peopled by nine white men, and six men and twelve women of Tahiti. In 1800 the population consisted of one man, five women, and nineteen children; and the descendants of these persons are stated by later travellers to be strong and healthy without any traces of degeneration. Omitting whatever else may be said against this case as evidence for the harmlessness of consanguineous marriages, I need only call attention to the facts that, since the colonization of this island, a few strangers have joined the little colony; that it was once removed to Norfolk Island, and that, of those who returned, one was a Norfolk Islander who had married a Pitcairn girl; that the island has frequently been visited by ships with their crews;[2013] and that, as Beechey expressly states, the same restrictions with regard to intermarriage of relations exist here as in England.[2014]