Consanguineous Marriages in the American Population Part 2

The completed formula then becomes:

All same-name marriages 100 1 -------------------------- = ----- X --- = .35 (nearly) All first cousin marriages 57 5

Applying this formula to the English statistics, Mr. Darwin computes the percentages of first cousin marriages in England with the following results:

--------------------------------------- London | 1.5 Other urban districts | 2.

Rural districts | 2.25 Middle cla.s.s and Landed Gentry | 3.5 Aristocracy | 4.5 ---------------------------------------

In order to apply this formula to the American population I counted the names in the New York Marriage License Record previous to 1784,[25] and found the number to be 20,396, representing 10,198 marriages. The fifty commonest names embraced nearly 15 per cent of the whole (1526), or three per cent less than the number found by Darwin.[26] Of these, one in every 53 was a Smith, one in 192 a Lawrence, and so on. The sum of the fraction 1/53^2, 1/192^2, etc., I found to be .000757 or .757 per thousand, showing that the probability of a chance marriage between persons of the same name was even less than in England, where Mr. Darwin considered it almost a negligible quant.i.ty.

[Footnote 25: _Names of Persons for whom Marriage Licenses were issued by the Secretary of the Province of New York_.]

[Footnote 26: _Cf. supra_, p. 21.]

Of these 10,198 marriages, 211, or 2.07 per cent were between persons bearing the same surname. Applying Darwin's formula we would have 5.9 as the percentage of first cousin marriages in colonial New York.

This figure is evidently much too high, so in the hope of finding the fallacy, I worked out the formula entirely from American data. To avoid the personal equation which would tend to increase the number of same-name first cousin marriages at the expense of the same-name not first cousin marriages, I took only those marriages obtained from genealogies, which would be absolutely unbia.s.sed in this respect. Out of 242 marriages between persons of the same name, 70 were between first cousins, giving the proportion:

Same-name first cousin marriages 70 -------------------------------- = --- = .285 All same-name marriages 242

as compared with Darwin's .57. So that we may be fairly safe in a.s.suming that not more than 1/3 of all same-name marriages are first cousin marriages. Taking data from the same sources and eliminating as far as possible those genealogies in which only the male line is traced, we have it:

Same-name first cousin marriages 24 1 1 ------------------------------------- = -- = -------- = ------- Different-name first cousin marriages 62 (2-7/12) 2.583

This is near the ratio which Darwin obtained from his data, and which he finally changed to 1/4. I am inclined to think that his first ratio was nearer the truth, for since we have found that the coefficient of attraction between cousins would be so much greater than between non-relatives, why should we not a.s.sume that the attraction between cousins of the same surname should exceed that between cousins of different surnames? For among a large number of cousins a person is likely to be thrown into closer contact, and to feel better acquainted with those who bear the same surname with himself. But since the theoretical ratio would be about 1/4 it would hardly be safe to put the probable ratio higher than 1/3, or in other words four first cousin marriages to every same-name first cousin marriage. Our revised formula then is:

All same-name marriages 3 1 --------------------------- = --- X --- = .75 All first cousin marriages 1 4

Instead of Mr. Darwin's .35.

Taking then the 10,198 marriages, with their 2.07 per dent of same-name marriages, and dividing by .75 we have 2.76 per cent, or 281 first cousin marriages.

In order to arrive at approximately the percentage of first cousin marriages in a nineteenth-century American community I counted the marriage licenses in Ashtabula County, Ohio, for seventy-five years, (1811-1886). Out of 13,309 marriages, 112 or .84 per cent were between persons of the same surname. Applying the same formula as before, we find 1.12 per cent of first cousin marriages, or less than half the percentage found in eighteenth-century New York. This difference may easily be accounted for by the comparative newness of the Ohio community, in which few families would be interrelated, and also to that increasing ease of communication which enables the individual to have a wider circle of acquaintance from which to choose a spouse.

Adopting a more direct method of determining the frequency of cousin marriage, I estimated in each of sixteen genealogical works, the number of marriages recorded, and found the total to be 25,200. From these sixteen families I obtained 153 cases of first cousin marriage, or .6 per cent. Allowing for the possible cases of cousin marriage in which the relations.h.i.+p was not given, or which I may have over-looked, the true percentage is probably not far below the 1.12 per cent obtained by the other method.

The compiler of the, as yet, unpublished Loomis genealogy writes me that he has the records of 7500 marriages in that family, of which 57 or .8 per cent are same-name marriages. This would indicate that 1.07 per cent were between first cousins.

In isolated communities, on islands, among the mountains, families still remain in the same locality for generations, and people are born, marry and die with the same environment. Their circle of acquaintance is very limited, and cousin marriage is therefore more frequent. If we exclude such places, and consider only the more progressive American communities, it is entirely possible that the proportion of first cousin marriages would fall almost if not quite to .5 per cent. So that the estimate of Dr. Dean for Iowa may not be far out of the way.

Even for England Mr. Darwin's figures are probably much too large.

Applying the corrected formula his table becomes:

TABLE VI.

---------------------------------------------------- |Number |Per cent of|Per cent of 1872. |marriages |same-name |first cousin |registered.|marriages. |marriages.

---------------------------------------------------- London, | | | Metropolitan | | | Districts | 33,155 | .55 | .73 Urban Districts| 22,346 | .71 | .95 Rural Districts| 13,391 | .79 | 1.05 ---------------------------------------------------- Total | 68,892 | .64 | .85[A]

---------------------------------------------------- [A] Cf. Mulhall, .75 per cent, _supra_, p. 18.

In regard to the frequency of marriage between kin more distant than first cousins figures are still more difficult to obtain. The distribution of 514 cases of consanguineous marriage from genealogies was as follows:

TABLE VII.

--------------------------------------------------------------------- | First | 1-1/2 |Second | 2-1/2 | Third |Distant| |cousins|cousins|cousins|cousins|cousins|cousins|Total --------------------------------------------------------------------- Same-name | 70 | 24 | 49 | 19 | 20 | 26 | 208 Different-name| 96 | 30 | 58 | 22 | 37 | 62 | 305 --------------------------------------------------------------------- Total | 166 | 54 | 107 | 41 | 57 | 88 | 513 ---------------------------------------------------------------------

Obviously this cannot be taken as typical of the actual distribution of consanguineous marriages, since the more distant the degree, the more difficult it is to determine the relations.h.i.+p. However it is very evident that the coefficient of attraction is at its maximum between first cousins, and probably there are actually more marriages between first cousins than between those of any other recognized degree of consanguinity. But the two degrees of 1-1/2 cousins and second cousins taken together probably number more intermarriages than first cousins alone. Allowing four children to a family, three of whom marry and have families, the actual number of cousins a person would have on each degree would be: First, 16; 1-1/2, 80; Second, 96; 2-1/2, 480; Third, 576; Fourth, 3,456. The matter is usually complicated by double relations.h.i.+ps, but it will readily be seen that the consanguineal attraction would hardly be perceptible beyond the degree of third cousins.[27]

[Footnote 27: See note, _infra_, p. 29.]

Omitting, as in the discussion on page 24, those genealogies in which only the male line is given we have the following table:

TABLE VIII.

-------------------------------------------------------------------- |First | 1-1/2 |Second | 2-1/2 | Third |Distant| |cousins|cousins|cousins|cousins|cousins|cousins|Total -------------------------------------------------------------------- Same-name | 24 | 5 | 10 | 4 | 2 | 5 | 50 Different-name| 62 | 15 | 33 | 12 | 23 | 26 | 171 -------------------------------------------------------------------- Total | 86 | 20 | 43 | 16 | 25 | 31 | 221 --------------------------------------------------------------------

It would naturally be supposed that with each succeeding degree of relations.h.i.+p the ratio of same-name to different-name cousin marriages would increase in geometrical proportion, viz. first cousins, 1:3; second cousins, 1:9; third cousins, 1:27, etc., but on the other hand there is the tendency for families of the same name to hold together even in migration as may be proved by the strong predominance of certain surnames in nearly every community. So that the ratio or same-name to different-name second cousin marriage may not greatly exceed 1:4. Beyond this degree any estimate would be pure guesswork.

However the coefficient of attraction between persons of the same surname would undoubtedly be well marked in every degree of kins.h.i.+p, and conversely there are few same-name marriages in which some kins.h.i.+p, however remote, does not exist.

The proportion of mixed generation cousin marriages (1-1/2 cousins, 2-1/2 cousins, etc.) is always smaller than the even generation marriages of either the next nearer or more remote degrees. For example, a man is more likely to marry his first or his second cousin than either the daughter of his first cousin, or the first cousin of one of his parents, although such mixed generation marriages often take place.

The conclusions, then, in regard to the frequency of consanguineous marriage in the United States may be summarized as follows:

1. The frequency varies greatly in different communities, from perhaps .5 per cent of first cousin marriages in the northern and western states to 5 per cent, and probably higher, in isolated mountain or island communities. The average of first cousin marriage in the United States is probably not greater than one per cent.

2. The percentage of consanguineous marriages is decreasing with the increasing ease of communication and is probably less than half as great now as in the days of the stage coach.

3. Although the number of marriageable second cousins is usually several times as great as that of first cousins, the number of marriages between second cousins is probably somewhat less than the number of marriages between first cousins, but the number of second cousin marriages combined with the number of 1-1/2 cousin marriages probably exceeds the number of first cousin marriages alone. So that the percentage of marriages ordinarily considered consanguineous is probably between two, and two and a half.

NOTE.--In an article ent.i.tled "Sur le nombre des consanguins dans un groupe de population," in _Archives italiennes de biologie_ (vol.

x.x.xiii, 1900, pp. 230-241), Dr. E. Raseri shows that from one point of view the actual number of consanguineous marriages is little, if any, greater than the probable number. The average number of children to a marriage he finds to be 5, the average age of the parents 33 and the average age at marriage 25. The Italian mortality statistics show that 54 per cent of the population lives to the age of 25, of which 15 per cent does not marry, leaving an average of 2.3 children in every family who marry. On this basis a person would have at birth 4,357 relatives within the degree of fourth cousins; at the age of 33 he would have 4,547; and at 66, 5,002. In 1897 out of 229,041 marriages in Italy, 1,046 were between first cousins, giving an average of one in 219. In 1881 the number of men between 18 and 50 and of women between 15 and 45 was 5,941, 495 in 8,259 communes with an average population of 3,500. In each commune there must be 360 marriageable persons of each s.e.x, but to marry within his cla.s.s a man would only have the choice of 180 women and vice versa. Adding the probable number who would marry outside the commune, the choice lies within 216 of the opposite s.e.x. Of these 25 would be cousins within the tenth degree (fourth cousins) making the probability of a consanguineous marriage .11, reduced by a probable error in excess to .10. The probability of a first cousin marriage would be .82/216 or .0038, whereas the actual ratio is 1/219 or .0045.

CHAPTER III

MASCULINITY

The predominance of male over female births is almost universal, although varying greatly in different countries and under different conditions. This fact has given rise to the term Masculinity, which conveniently expresses the proportion of the s.e.xes at birth. The degree of masculinity is usually indicated by the average number of male births to every 100 female births. The cause of this preponderance of males is still a mystery, and will definitely be known only when the causes of the determination of s.e.x are known.

Since, however, it is well known that infant mortality is greater among males than among females, positive masculinity is necessary to keep up the balance of the s.e.xes, and therefore seems to be an essential characteristic of a vigorous and progressive race.

Within recent years the theory has prevailed among certain sociologists that positive masculinity is stronger in the offspring of consanguineous marriages than in the offspring of unrelated parents.

Professor William I. Thomas in his writings and lectures a.s.serts this as highly probable.[28] Westermarck,[29] to whom Professor Thomas refers, quotes authorities to show that certain self-fertilized plants tend to produce male flowers, and that the mating of horses of the same coat color tends to produce an excess of males.[30]

[Footnote 28: _s.e.x and Society_, p. 12.]

[Footnote 29: _History of Human Marriage_, p. 476.]

[Footnote 30: _Goehlert, Ueber die Vererbung der Haarfarben bei den Pferden._ Quoted by Westermarck, p. 476.]

Westermarck continues, quoting from Dusing:[31] "Among the Jews, many of whom marry cousins, there is a remarkable excess of male births. In country districts, where, as we have seen, comparatively more boys are born than in towns, marriage more frequently takes place between kinsfolk. It is for a similar reason that illegitimate unions show a tendency to produce female births."