Consanguineous Marriages in the American Population Part 4

[Footnote 42: Woods, _Heredity in Royalty_, pp. 74-75. The Great Elector, a great-grandson of William the Silent, married his 1-1/2 cousin, a granddaughter of William and also a great-granddaughter of Admiral Coligny. Frederick I married his second cousin, daughter of the d.u.c.h.ess Sophia of Brunswick, and a descendant of William.

Frederick William I married his first cousin, Dorothea, granddaughter of Sophia, and also a descendant of William the Silent. Unfortunately the Hohenzollern line was continued by a mediocre brother of Frederick II, but through his sister, Queen Ulrica, the line of genius lasted still another generation to Gustavus III of Sweden.]

The ills which have at one time or another been attributed to consanguineous marriage include nearly all those which cannot otherwise be satisfactorily accounted for. But with the progress of pathology the list has greatly been reduced: for instance, cretinism is now known to be a product of local conditions. The remaining counts in the indictment against consanguineous marriage may roughly be cla.s.sified as: 1. The production of infertility, some forms of physical degeneracy, and deformity. 2. The production or aggravation of mental and nervous disorders. 3. The production of certain defects in the organs of special sense. These three divisions will be discussed separately.

1. INFERTILITY AND DEGENERACY

Although there has never been any considerable evidence for the first of these charges, it has frequently been repeated. Professor Montegazza of the University of Pavia collected data in regard to 512 cases of consanguineous marriage of which between 8 and 9 per cent were sterile, and with this basis he a.s.serts that sterility is the only fact which can safely be deduced from his cases, since it cannot be hereditary.[43] But if in the nature of things absolute sterility is not inheritable, comparative infertility may be. And even then 8 or 9 per cent does not seem to be an excessively high proportion of sterility, especially if late marriages be counted. Boudin bases his a.s.sertion on this point on even less tenable grounds.[44] On the other hand some writers a.s.sure us that cousin marriages are even more prolific and less liable to sterility than the average.

[Footnote 43: See Darwin, "Marriages between First Cousins in England and Their Effects," _Journal of Statistical Society_, June, 1875, p.

178.]

[Footnote 44: Boudin, "Crois.e.m.e.nt des familles, de races et des especes." In _Memoires de la Societe d' Anthropologie_, vol. i, p.

518.]

The most important statistical investigation was made by G.H.

Darwin.[45] From his genealogical data he compiled the following table:

TABLE XVI.

------------------------------------------------------------------------ | | Average | |Ave. no.

| | number | Per cent |sons to |Number of | sons to | sterile |fertile |marriages.| marriage. | marriages. |marriage.

------------------------------------------------------------------------ Not consanguineous | 217 | 1.91 | 15.9 | 2.26 Parents 1st cousins[A] |97 to 105 |2.07 to 1.92|14.7 to 20.9| 2.43 One parent offspring of | | | | 1st cousin marriages. | 93 | 1.93 | 17.2 | 2.34 ------------------------------------------------------------------------ [A] Eight cases of doubtful fertility.

[Footnote 45: Op. cit., p. 181.]

It will readily be seen that the conclusion is negative, since the variation is slight, but the higher fertility of the cousin marriages is interesting.

On the other hand de Lapouge quotes a case of a community founded two centuries ago by four families and populated almost entirely by their descendants, in which from 1862 to 1886 there were 273 marriages of which 63 were consanguineous and 26 were between first cousins. Among the non-consanguineous 3 per cent were uniparous, as against 7.95 per cent among the consanguineous. 7.5 per cent of the non-consanguineous were sterile as against 16 per cent of the consanguineous.[46] The importance of these percentages is impaired by the fact that they involve only five uniparous families and ten sterile ones, and that of these latter only five were sprung from first cousins.

[Footnote 46: De Lapouge, _Les Selections Societies_, p. 196.]

It is almost impossible to get any accurate statistics of sterility from genealogies, for when no children are given in the record, there is always a strong possibility that there were children of whom the genealogist has no record. However, of 16 first-cousin marriages of which the record expressly stated "no issue," or where it was practically certain that no issue was possible, the average age of the brides was 34.3 years and that of the grooms was 39 years, showing that consanguinity could not have been the only cause of their sterility.

In regard to relative fertility the figures are reliable, but they fail to indicate any effect of consanguinity upon fertility, as will be noted in Table XVII.

TABLE XVII.

------------------------------------------------------------- |No. of | | Ave. to |fertile | No. of | fertile Parentage. |marriages.|children.|marriage.

------------------------------------------------------------- First cousin. Gene. | 125 | 672 | 5.4 First cousin. Cor. | 150 | 759 | 5.1 Double cousins and uncle-niece| 9 | 39 | 4.3 Other consanguineous | 333 | 1605 | 4.8 Non-related | 676 | 3417 | 5.1 Ch. of 1st cousins | 294 | 1395 | 4.7 All consanguineous | 617 | 3075 | 5.0 All non-related | 970 | 4812 | 5.0 -------------------------------------------------------------

The report of Dr. Bemiss, and the report of the Ohio commission[47]

which he quotes, give the following figures:[48]

TABLE XVIII.

------------------------------------------------------- | No. of | | Ave. to | fertile | No. of | fertile Parentage. |marriages.|children.|marriages.

------------------------------------------------------- 1st cousins or nearer[A]| 660 | 3363 | 5.0 More distantly related | 119 | 572 | 4.8 Non-consanguineous | 125 | 837 | 6.7 Ohio consanguineous | 155 | 1021 | 6.6 Ohio non-consanguineous | 200 | 1375 | 6.9 ------------------------------------------------------- [A] Includes double-cousins and uncle-niece marriages.

[Footnote 47: Appointed to ascertain the number of the deaf and dumb, blind, idiotic and insane within the State.]

[Footnote 48: See Bemiss, in _Trans. of Am. Med. a.s.so._, vol. xi, 1858, pp. 420-425.]

The comparatively low averages of the consanguineous marriages from Bemiss may easily be accounted for by the fact that the cases were highly selected so that nearly one-third of the children were in some way defective, and the parents in many cases were far below the average in vitality. The "more distantly related" are in a still lesser degree representative of the cla.s.s, since out of a greater possibility of choice a smaller number were chosen. The "non-consanguineous" were supposed to be near the average in vitality and fertility.

In Norway, according to Uchermann, the consanguineous and the non-consanguineous marriages are equally fertile, averaging 6.1 children per marriage;[49] and in a Black Forest village Tenckhoff found an average of 4.6 children to each consanguineous marriage as against 3.5 to each non-consanguineous marriage.[50] In regard to the youthful death-rate among the offspring of consanguineous marriages, comparison with non-related marriages is more feasible. I have counted in each case all those children who are known to have died under the age of twenty. This age was taken for the sake of convenience, and to include all children indefinitely specified as having "died young."

The results are given in Table XIX:

TABLE XIX.

------------------------------------------------- Parentage. | No. of |No. dying | (Genealogies.) |Children.|under 20. |Per cent.

------------------------------------------------- First cousins | 672 | 113 | 16.7 Other cousins | 1417 | 211 | 14.9 Ch. of 1st cousins| 825 | 103 | 12.5 Non-consanguineous| 3184 | 370 | 11.6 ------------------------------------------------- (Correspondence.) ------------------------------------------------- First cousins | 759 | 88 | 11.6 Other marriages | 829 | 71 | 8.6 -------------------------------------------------

[Footnote 49: Feer, _Der Einfluss der Blutsverwandschaft der Eltern auf die Kinder,_ p. 12, _note_.]

[Footnote 50: Ibid.]

If the figures in Table XIX are to be accepted at their face value, and there seems to be no good reason for not doing so in the genealogical cases at least, the youthful death-rate among the offspring of consanguineous marriages far exceeds the average. The average in the correspondence cases is undoubtedly too low, as many correspondents failed to report the deaths. From the fact that a comparatively large percentage of these were reported as defective, we should expect a higher death-rate than among the unbiased genealogical cases.

Dr. Bemiss found a very high death-rate among the children of consanguineous marriage, due partly to the fact that his cases were reported by physicians. He reports that of the offspring of marriages between first cousins and nearer relatives, 23 per cent "died young;"

of the offspring of more remote consanguineous marriages, 16 per cent; and of non-related marriages 16 per cent. There is, therefore, a strong indication of lowered vitality as a result of consanguineous marriage.

A determination of even the approximate percentage of degenerate offspring resulting from marriages of consanguinity by direct inquiry is exceedingly difficult. The average human mind is so const.i.tuted as to exaggerate unconsciously the unusual in its experience. Herein lies the fallacy in the work of Dr. Bemiss. His material was "furnished exclusively by reputable _physicians_ in various states," and of the 3942 children of consanguineous marriages in the cases thus furnished him, 1134 or 28.8 per cent were in some way "defective." Of these, 145 were deaf and dumb, 85 blind, 308 idiotic, 38 insane, 60 epileptic, 300 scrofulous and 98 deformed. It is evident that a physician in reporting such data to a physician would naturally give cases in which something pathological existed. Even if there were no conscious bias, such cases would be the ones with which a physician would be most likely to come in contact. Dr. Bemiss himself recognized the possibility of this bias. To quote him:

It is, natural for contributors to overlook many of the more fortunate results of family intermarriage, and furnish those followed by defective offspring and sterility. The mere existence of either of these conditions would prompt inquiry, while the favorable cases might pa.s.s unnoticed. Contributors have been particularly requested to furnish without prejudice or selection all instances of the marriage of consanguinity within their various circles of observation, whatever their results.[51]

[Footnote 51: Bemiss. see _Trans. of Am. Med. a.s.so._, vol. xi, 1858, p. 323.]

Yet he does not seem to believe that this bias seriously affects his conclusions.

In order as far as possible to avoid this bias, I sent my own circulars to genealogists and others who would naturally be more interested in the relations.h.i.+ps than in pathological conditions. I asked, however, that all such results be noted. Among 722 children of first cousins I found 95 or 13 per cent who were defective in the sense in which Bemiss used the term. This is much nearer the actual percentage, but I have reason to believe, as will be seen hereafter, that even this percentage is far too high. A good ill.u.s.tration of the unconscious bias, which I tried to avoid is afforded by the reports on the cause of death among children of first cousins. Only 58 replies were given to this question, and of the 58 deaths 14 or one-fourth were either accidental or otherwise violent, while only one person was reported to have succ.u.mbed to pneumonia.

Many efforts have been made to investigate the occurrence of degeneracy in the offspring of consanguineous marriages, by studying communities in which such unions have been frequent, but the results are untrustworthy. Huth[52] quotes a number of instances where communities have lived for generations without crosses and with no apparent degeneracy, while other writers tell of high percentages of degeneracy. Smith's Island, Maryland, as has been said, seems absolutely free from serious congenital abnormalities, in spite of the great frequency of consanguineous marriages.

[Footnote 52: _Marriage of Near Kin_, chap. iv.]

The causes of degeneracy are so varied, complicated, and obscure that even if consanguinity is a cause, there can be but few cases in which it is not complicated by other factors. But for the same reason that it is so difficult to prove any connection between consanguinity and degeneracy, it is equally difficult to disprove such a connection. It is very probable that from the mere operation of the law of heredity, there must be a comparatively large percentage of degenerates among the offspring of related parents, for defects which tend to be bred out by crossing are accentuated by inbreeding. This may be the reason for the disagreement among investigators of isolated communities. If an island, for instance, were settled by a small group of families in even one of which some hereditary defect was common, in the course of a few generations that defect would be found in a relatively large part of the population. While if the same island were settled by perfectly sound families, there would only be a remote chance of any particular defect appearing. Thus both cla.s.ses of investigators may be perfectly conscientious, and yet arrive at diametrically opposite results. This theory is at least not to be contradicted by any facts which have come to light in the present investigation.

Some interesting points are brought up in Dugdale's well-known study of the "Jukes."[53] This family, of about 540 persons living in northern New York, is descended from five sisters of unknown parentage, who were born between 1740 and 1770. The name "Juke" is fict.i.tious, and is applied to all descendants of these five women, little attempt being made to trace the male lines on account of the excessive prevalence of illegitimacy.

[Footnote 53: R.L. Dugdale, _The Jukes_]

In this family consanguineous marriages have been very frequent, perhaps partly because the Jukes came to be looked upon as pariahs and could not a.s.sociate on equal terms with other members of the community. These marriages seem to have been fully as productive as the average of the family, and the offspring of as high a grade of intelligence. However, some individual cases are worthy of special mention as ill.u.s.trative of intensification of hereditary tendencies.

(1) An illegitimate son of Ada Juke married a daughter of Bell Juke.

He was a laborer, honest and industrious. She was reputable and healthy, and her father had a good reputation, but her mother had given birth to four illegitimate children before marriage, three of whom were mulattoes. Thus in this marriage of first cousins, three out of the four parents were of a low moral grade. As a result of this marriage three sons and three daughters were born. Two sons were licentious, intemperate and dishonest, two daughters were prost.i.tutes, and the third became such after her husband was sent to prison. Only one son turned out fairly well. This son married a second cousin, a granddaughter of Delia Juke, and four out of his seven children were above the average of the family. His two elder brothers, however, married prost.i.tutes, and became ancestors of criminals, prost.i.tutes and syphilitics.[54]

[Footnote 54: Ibid., Chart I.]

(2) A legitimate son of Ada Juke, whose father was a thief and a pauper, married a daughter of Clara Juke, whose antecedents were fairly good. The husband had contracted syphilis before marriage and entail it upon every one of his eight children. Five daughters became prost.i.tutes and one was idiotic. The only daughter who bore a good reputation married a grandson of both Clara and Bell Juke. This was a remarkable case of selection. Both husband and wife were grandchildren of Clara, and so first cousins, and both were the offspring of first cousins, all within the Juke blood. But, on the other hand, both were the descendants of Clara, the best of the Juke sisters, and both were the best of the progeny of their respective parents. The only serious taint was the secondary syphilis which the wife had inherited from her father. Six children were born, two males and four females. The eldest son was at 31 "laborer, industrious, temperate;" the eldest daughter "good repute, temperate, read and write;" second daughter, "harlot;"

third daughter "good repute, temperate;" and the two youngest are given simply as "unmarried." This family seems to have had as high an average mentally and morally as any family in the whole tribe, only one in six being distinctly immoral. In the next generation, the eldest son had two children, the eldest daughter four, and the third daughter, who married a first cousin, had one child. It would be of great interest to know more of this last marriage, the third generation of consanguinity in marriage, and the fourth first-cousin marriage in three generations, but at the time the book was written the parties were still in their early twenties.[55]