Consanguinity

CONSANGUINITY (Latin consanguinitas; Greek ὁμοιμότης = being of the same blood).

I. BIOLOGY

According to its etymological and literal meaning, c. is the attribute of individuals having the same blood and essentially expresses, following the acquisitions of modern genetics, the biological relationship existing between individuals to whom one and the same gene pool (that is, the same complex of hereditary factors or genes that realize the characters) has been hereditarily transmitted (in whole or in part). In other words, biologically, consanguineous are all those belonging to the same kinship in the genetic sense (or stock or lineage), that is, to the whole of one and the same family, plus all ascendants and descendants. In 1927 van Bemmelen (cited by R. R. Gates) proposed using the term "parentage" to indicate all the descendants of a particular "couple."

In nature, one and the same gene pool can be transmitted totally or partially. Total transmission occurs: in individuals born from the same parent by asexual reproduction, or by parthenogenetic reproduction (without fertilization of the egg), or by autogamous sexual reproduction (self-fertilization), as happens in plants and lower animals. All individuals generated according to such forms of reproduction have an identical gene pool and are therefore totally consanguineous; they are, accordingly, considered genetically pure. Partial transmission of one and the same gene pool occurs, instead, in individuals generated by cross-fertilization (allogamy), that is, by the union of the sexual cells of two individuals of different sex, as happens in higher plants and animals and in man. All individuals born allogamically have, among themselves, a gene pool only partially identical and deriving half from the paternal one and half from the maternal one; they are therefore only partially consanguineous and are considered genetically hybrid. However, it can happen - whether naturally, as in the case of univular twins, that is, deriving from the division of one and the same fertilized egg, or artificially, through repeated consanguineous matings, forbidden in man - that even for those born from cross-fertilization, there exists an identity of the respective gene pools.

Finally, the term c. is also used in geology (on the proposal of Iddings in 1802) to indicate the chemical and mineralogical commonality existing between eruptive rocks deriving from one and the same magma and constituting one and the same "petrographic province."

II. CONSANGUINEOUS MATINGS

The forms of allogamous sexual reproduction (characteristic of higher plants and animals and of man), that is, reproduction brought about through the crossing of two individuals of different sex (parents), are divided into endogamous and exogamous, according to whether the two parents belong (endogamy) or do not belong (exogamy) to the same group of kinship or, in a broader sense, only for man, to the same caste or the same marriage class (primitive peoples).

Consanguineous matings are therefore endogamous reproductions, of which the most elementary form is that of the union between brother and sister.

History reminds us that consanguineous marriages were practiced in antiquity to preserve the purity of blood and of genealogical traditions, especially in royal families, among which are cited those of the Incas in Peru and of the Pharaohs in Egypt; Herodotus and Strabo relate that consanguineous marriages were authorized among the Medes, the Persians, etc.

Ethnology informs us that matings between brothers and sisters are still common (as Corso reports) in various places, in the higher social classes and in the royal families of Baghirmi, Darfur, Siam, Ceylon, Hawaii, etc. Moreover, among many primitive peoples, the union between consanguineous kin is a taboo (prohibition); the tribes are divided into two sections, each called a marriage class, which can be subdivided into subgroups called phratries, each in turn divisible into clans, within which the members consider themselves brothers and cannot marry one another. It can happen, however, where matriarchy exists, as among the Iroquois, that a man of a particular clan, having married two women of two different clans, has children who, belonging to two different clans, can mate with one another. Among other primitive peoples (Akicua and other ethnic groups of Africa) the violation of the taboo, committed through marriage between two consanguineous kin who, however, did not know they were such, can be repaired by magical procedures that symbolically kill the bond of kinship and render the union of that couple no longer prohibited.

Small ethnic nuclei with high endogamy are also found in Europe, Switzerland, Sweden, etc., and generally in zones with geographic isolation, such as the Alpine ones, rural areas, etc.

III. ETHNOGRAPHY

Can the prohibition of marriage between blood relatives, sanctioned in the legislations of civilized nations, represented in the taboos of primitive peoples, evidently determined by reasons of a social, moral and political order, also be supported by reasons of a biological order?

In higher plants and animals, already for centuries past, breeders, empirically, after having obtained new varieties through special crosses, had succeeded in maintaining them by means of repeated, successive strictly endogamous reproductions (that is, by mating with one another the offspring of the same pair) which have rendered ever purer and more evident certain characters particularly sought after for utilitarian and commercial purposes, such as, for example, the capacity for a greater production of milk, or of eggs, or of wool, for greater speed in running, etc. In this way breeds have become stabilized which later became famous, such as the Durham and Hereford cattle breeds, the English thoroughbred horse breeds, the Ancon sheep breeds of Massachusetts (with short legs that do not allow them to jump fences), etc. These results have demonstrated that consanguineous matings render stable and always manifest that or those characters which, otherwise, with non-consanguineous crosses, would have remained latent (recessive), that is, not manifest and therefore not exploitable. Therefore, as the advances of modern genetics have increasingly confirmed, consanguineous matings, by increasing the probability of combinations of identical genes, render more frequent the manifestation of the respective characters.

Thus one could, perhaps, explain the phenomenon observed in plants and known by the name of "hybrid luxuriance or heterosis," consisting in the greater robustness of individuals generated by exogamous crosses, compared with the weakness of those originating from autogamy; with heterosis, in fact, any unfavorable recessive genes have a greater probability of not being found together and therefore remain more frequently latent. On the other hand, the cross between closely related but distinct species, when it is fertile, can originate infertile individuals as occurs with the mule. However, the intimate mechanism of the phenomenon of heterosis is still much debated and, according to Gates, there exists no strictly genetic proof of its occurring in the human race.

In man, marriages between blood relatives have been the subject of numerous investigations, not always concordant in their conclusions, some of which are reported by way of example.

Elderton (1911), studying marriages between cousins in England, found that consanguineous mating did not necessarily lead to a higher infant mortality, while it was found with decidedly greater frequency in the parents of albinos, of the deaf-mute, of the mentally defective. She therefore concluded that in the community there existed a very large number of latent defects (recessive genes).

Murphy (1924) described a family that had emigrated from Germany to Pennsylvania in 1731. The original emigrant left 24 children, one of whom settled in North Carolina in 1797. The families remained prolific and there were, in 4 generations, 7 marriages between first cousins. Among the descendants no physical abnormalities were found, and only one had a slightly deficient intelligence; there were noted, however, a high infant mortality and a death rate decidedly higher than in the common population.

Mohr and Wriedt (1928), cited by Gianferrari and Cantoni, "reported the case of an abortive fetus that presented the upper extremities amputated, skeletal alterations in the lower limbs and an inguinal hernia; the parents were first cousins."

Bell (1940), following an investigation of 49,000 patients in the hospitals of England and Wales, found that the children of blood relatives constituted 0.97% and the children of first cousins 0.61%, percentages that seem too low.

Rondoni (1947) gives the example of "our great biologist Golgi who, having lived in full physical and mental efficiency until an advanced age, was the son of cousins." Moreover, reporting the case of Turkalj-Aschner who would have observed a harmful effect in marriage between cousins even in the second generation (a woman with severe skeletal anomalies and imbecilic was the daughter of a father born from a marriage between cousins: a gene that remained latent in the father?), Rondoni, in comment, writes verbatim: "yet, not even this author would entirely proscribe marriages between blood relatives, if there are no hereditary affections in the lineage and if, on the contrary, a eugenic advantage (high intellectual endowments) is to be expected."

And Rössle, who investigated the lesions and causes of death in individuals with different degrees of consanguinity, wrote: "no people has declined through an increase of hereditary diseases but rather through impairments due to other causes" and "there do not hang over those families as many swords of Damocles as one would expect from the study of genetics textbooks" (cited by Rondoni).

In summary, for man, contrary to what was believed in the past, today it is concordantly admitted that the dangerousness, for the descendants of unions between blood relatives, does not reside in the consanguinity in itself considered, but in the possible existence of family taints which, from the consanguineous union, could be rendered actual or aggravated, while with the non-consanguineous union they could remain latent or be milder. Consanguineous matings, therefore, by exalting the dominant characters (Mohr) or by bringing to light the recessives present in a given genealogical stock, are not the determining and fatal cause of the degenerative manifestations of the descendants, but only the means that strengthens or brings to light the hereditary characters, whether favorable or unfavorable.

Therefore, all the diseases considered certainly or presumably hereditary and which, manifest or latent, pre-existed in a given family stock, can be called into question in consanguineous matings. Of these, indeed, modernly account is taken in order to establish whether the pathogenic genes of a given disease are dominant (that is, they always realize the disease which, therefore, does not skip generations and occurs with a frequency independent of consanguinity), or recessive (that is, they realize the disease only when in the gene patrimony of the proband the corresponding dominant gene [allele] is missing, that is, when such recessive genes have been transmitted, as is also commonly said, in double dose [v. GENETICA]). The pathological manifestations realized by them therefore skip generations and are more frequent in the descendants of blood relatives than in the rest of the population.

It should be borne in mind, however, that the same anomaly or morbid affection can present, in different stocks, a different hereditary course (now dominant, now recessive, now sex-linked recessive), which, however, for the same stock is always the same.

To cite a few examples, there are recalled: universal albinism (lack of pigment in the skin, hair, irises) which represents a classic example of an anomaly of a recessive character, for which the consanguinity of the parents has been found in 35%-50% of those affected and, according to Sanders (1938) in Holland, to an extent 15 times greater than in the general population; retinitis pigmentosa or pigmentary retinal dystrophy (presence of patches of pigment in the retina with progressive reduction of central vision) which can present with a simple recessive character (with a high rate of consanguinity among the ancestors of those affected) and, more rarely, with a dominant character or a sex-linked recessive character (males affected); it can be associated with deaf-mutism (Usher syndrome) and with various other malformations and oligophrenia (Laurence-Moon-Bardet-Biedl syndrome); and the list could continue until it includes all the hereditary diseases to which reference is made.

Venerando Correnti

IV. LAW

The complex of juridical relationships among blood relatives, being an emanation of natural divine law, could not escape the dominion of positive law, whether divine or human. It must therefore be examined under the threefold aspect of natural divine law, positive divine law, and positive human law.

Natural law affects the juridical relationships among blood relatives along very general lines.

The whole complex of mutual rights and duties among blood relatives, in which their juridical relationships are resolved and which are summed up in the threefold mutual relation of reverence, dependence, and assistance, derives from the virtue of piety.

The juridical relevances of consanguinity are found first of all in positive divine law in general statements of principle, in direct dependence upon and application of natural law, and respectively as the basis of the norms sanctioned by positive human law.

In the first place, the fourth precept of the Decalogue: Honora patrem tuum et matrem tuam (Ex. 20:12; Deut. 5:16, etc.). St. Thomas explains the broad comprehensiveness of the divine precept (Sum. theol., 1a-2ae, 100, 5, ad 4); so broad that it is possible to deduce from it the sum of mutual rights and duties among blood relatives. Moreover, there is no lack in the divine law itself of norms that apply this deduction in all its vastness, both with regard to the mass of relatives (1 Tim. 5:8) and with regard to the sum of the rights and duties of consanguinity (Mt. 15:3-6). There are furthermore innumerable other statements and applications of particulars (cf., for example, Lev. 18:6 ff.).

Given the generality and indeterminacy of natural and positive divine law, positive human law found the way open to deduce more detailed and precise applications. For this reason, both in Roman law and in canon and civil law, there is found a system of norms far better adapted to the various exigencies of social life, according to their respective purposes and competences.

In consanguinity a distinction is made between the direct line (ascending or descending) and the collateral or oblique line; and, in each line, degrees.

Relatives in the direct line are those who descend one from the other (for example, children, parents, grandparents, etc.); relatives in the collateral or oblique line, on the other hand, are those who, while descending from the same person, do not descend one from the other (brothers, uncle and nephew, cousins, etc.). The computation of degrees in the direct line is done (and always has been done) by calculating how many persons separate the two relatives from each other, excluding however one of the two from the calculation: thus, for example, father and son are relatives in the first degree, grandfather and grandson in the second degree, great-grandfather and great-grandson in the third degree, and so on (cf. CIC, can. 96 § 2; Pius XII, motu proprio "Crebrae allatae," Feb. 22, 1949, can. 66 § 4 n. 2; art. 76 of the Italian Civil Code).

For the computation of degrees in the oblique line, two different systems are known.

The first (Roman method), now used in civil law everywhere, and in Eastern canon law, computes degrees by summing the distances of each of the two blood relatives from the common ancestor (cf. art. 76 of the Italian Civil Code; Pius XII, motu proprio "Crebrae allatae," Feb. 22, 1949, can. 66 § 4 n. 3). In this way two brothers are relatives in the second degree, each of them being one degree removed from the father, who is the common ancestor; uncle and nephew are relatives in the third degree, since the former is one degree and the latter two degrees removed from the ancestor, that is, from the father of the former and grandfather of the latter; two cousins are relatives in the fourth degree, each being two degrees removed from the common grandfather. Thus, for example, keeping in mind the diagram reproduced below, B and C are relatives in the first degree to A; D and E are relatives in the second degree to A; B and C are relatives in the second degree to each other;

The second (Germanic method), used, at least since the 6th century, in Latin canon law (cf. CIC, can. 96 § 3), computes degrees instead according to whichever of the two blood relatives is more distant from the common ancestor, without taking into account the distance of the other (or taking into account only one of the two distances, without summing them, in the case where they are equal). Therefore, with this method, two brothers, each being one degree removed from their common parent, are relatives in the first degree to each other; uncle and nephew are relatives in the second degree, counting only the longer distance, that is, that of the nephew, who is two degrees removed from the common ancestor; and likewise two cousins are relatives in the second degree. Thus, again referring to the diagram above, B and C are relatives in the first degree to A, their parent; D and E are relatives in the second degree to A, their grandfather; B and C are relatives in the first degree to each other; B and E in the second degree; C and D also in the second degree; D and E (cousins) also in the second degree.

It should further be noted that civil laws usually establish that consanguinity is not recognized beyond a certain degree (in Italy, up to the sixth inclusive, "except for certain specially determined effects": art. 77 of the Civil Code). In canon law there is no general norm, but the limit nonetheless exists: and precisely a de facto limit in consanguinity in the direct line, which can hardly have practical relevance beyond the second or third degree; legal limits, for consanguinity in the oblique line, limits moreover variable in relation to each of the juridical effects of consanguinity (the most remote degree to which one of these effects is attributed, namely that of producing an impediment to marriage, is the third degree in Latin law and the sixth in Eastern law: CIC, can. 1076 § 2; Pius XII, motu proprio cit., can. 66 § 2).

Setting aside the effects of consanguinity with regard to the acquisition of citizenship or domicile (v.), to paternal authority (v.) and to guardianship, and considering consanguinity as a matrimonial impediment, it is held that the impediment is certainly of natural law in the first degree of the direct line, and probably also in all the other degrees of the same line and in the first degree of the collateral line. In any case, positive human law has always had and still has precise and binding norms in this regard, certainly derived, at least in part, from divine law, whether natural or positive.

The Church, which in the first centuries accepted the impediment as diriment (v. IMPEDIMENT) within the limits of Mosaic legislation (Lev. 18:6; Deut. 27:20) and of Roman law (I, 1, 10), that is, between ascendants and descendants, brothers and sisters, aunts and nieces, extended it little by little, beginning in the 4th century, with legislation not always uniform in the various places nor always very clear (among other things, it was doubted whether, in the collateral line, beyond the fourth degree the impediment was diriment or only impedient). In the Latin Church, Innocent III, in can. 50 of the Fourth Lateran Council (of 1215), abolished the impediment for the collateral line beyond the fourth degree (can. 8, X, 4, 14); and this norm remained in force until 1918, the Council of Trent having rejected proposals to restrict the impediment. In the Eastern Church the history of the impediment of consanguinity in the oblique line is very different from rite to rite: in recent centuries almost all rites recognize the impediment up to the seventh or eighth degree of the Eastern computation.

The CIC now establishes, for the Latin Church, the prohibition and nullity of marriage between relatives, whether legitimate or natural, in the direct line in any degree, and in the collateral or oblique line up to the third degree inclusive (can. 1076 §§ 1-2). In Eastern canon law the impediment in the direct line extends likewise to infinity, in the oblique line instead up to the sixth degree inclusive, to be computed according to the different method already seen (Pius XII, motu proprio cit., can. 66 §§ 1-2).

The impediment of consanguinity is twofold, threefold, etc., in the case of consanguinity in a collateral line deriving from two, three, etc. common stocks (CIC, can. 1076 § 2; Pius XII, motu proprio cit., can. 66 § 2).

Three graphic examples of twofold consanguinity are given here. In the first example (fig. 1), since H is the son of E and of F, G and H have as common ancestors both A and B; they are therefore related to each other in the second degree of the Latin canonical computation or in the fourth of the Eastern (or civil) canonical computation through the ancestor B, but in the third degree of the Latin canonical computation or in the sixth of the Eastern (or civil) canonical computation through the ancestor B. In the second example (fig. 2), in which E is the son of B and D, F is the son of C and D, E and F have as common ancestors both A and D; they are related to each other in the first degree of the Latin canonical computation or in the second of the Eastern (or civil) canonical computation through the ancestor B (brothers), but in the second degree of the Latin canonical computation or in the fourth of the Eastern (or civil) canonical computation through the ancestor A (cousins). Finally, in the third example (fig. 3), in which G is the son of B and E, H is the son of C and F, G and H are related to each other twice in the second degree of the Latin canonical computation or in the fourth of the Eastern (or civil) canonical computation, once through the ancestor A and another time through the ancestor D.

If the existence of the impediment is doubtful, because it is not known whether the two who are to contract marriage are related or not, or in what degree, the marriage may be celebrated licitly, provided it is certain that they are neither relatives in a direct line nor brother and sister (CIC, can. 1076 § 3; Pius XII, motu proprio cit., can. 66 § 3), that is, in such a way that there is no danger of transgressing the divine law.

A dispensation from the impediment of consanguinity can be granted only when it is not of divine right, that is, only in the collateral line, and provided that it is not a case of brother and sister. The dispensation is granted for any reasonable motive when it is a case of consanguinity in the third degree in the law of the Latin Church, or in the sixth degree in that of the Eastern Church, since in that case it is an impediment of a lesser degree (CIC, can. 1042 § 2 n. 1; Pius XII, motu proprio cit., can. 31 § 1 n. 1); less easily in the closer degrees, and only for a grave cause between uncle (or aunt) and niece or nephew (cf. S. Congr. Sacram., Istruz., 1 Aug. 1931).

The Italian Civil Code precludes marriage for all ascendants and descendants in the direct line, legitimate or natural; and in the collateral line between sisters and brothers legitimate or natural and furthermore between uncle and niece, aunt and nephew (art. 87). It should be noted, however, that for marriages contracted before the Church, the State recognizes, on this point as well, canon law, while the norms of the Civil Code are applicable only to civil marriages and to non-Catholic ones (cf. art. 82 of the Civil Code).

Among the many personal effects of the c. mention is made only of some that reflect the incompatibility, that is, the exclusion of blood relatives from certain offices, the limitation or the evaluation of their testimony in court, the gravity or the imputability of certain crimes.

Regarding exclusion from certain offices, characteristic is that concerning the office of judge, which finds correspondence both in Roman law (D. 2, 1. 10) and in canon law (CIC, can. 1613 § 1), as well as in civil law (art. 51 ff. of the Code of Civil Procedure and art. 62 ff. of the Code of Criminal Procedure).

Traces of limitation, or rules for the evaluation of the judicial testimony of blood relatives, already existed in Roman law; they are, however, better determined in canon law (CIC, cann. 1755 § 2 n. 2; 1757 § 3 n. 3; 1974, 2027 § 1) and in civil law (arts. 247 and 246 of the Code of Civil Procedure; art. 350 of the Code of Criminal Procedure).

Finally, c. is a constitutive element of certain crimes such as incest (CIC, cann. 2357 § 1; 2359 § 2; art. 546 of the Penal Code) and parricide (art. 577 of the Penal Code; or else an aggravating circumstance in several others (cf. Penal Code, arts. 519 n. 2, 531 n. 2, 605 n. 1 etc.), and in some it is instead an exculpatory circumstance (Penal Code, art. 649).

c. is relevant, among other things, in the right and corresponding duty to means of subsistence (v. ALIMENTI), in the administration of property, but especially in successions (v. SUCCESSIONE).

Leaving aside up to this point any mention of the distinction between legitimate and illegitimate or natural c., it should be noted that the former derives from generation effected within marriage, the latter from generation outside marriage.

From the juridical point of view, the preference that belongs to legitimate c. is evident; if, on the other hand, illegitimate c., while having no title of legitimacy, not even natural (cf. Sum. theol., 3rd suppl., 68, 1), must and can have sufficient protection and assistance (cf. ibid., 2-3), this explains why positive law has always recognized or granted it a fairly extensive juridical relevance (v. FIGLIAZIONE).

Besides natural c., based on community of blood, the law has always recognized other kinds of analogous bonds, based on legal or spiritual relationships (v. AFFINITÀ; AGNAZIONE; COGNAZIONE).

Agatangelo da Lanzasco