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The following is a revision and update of the first edition entry "Eugenics and Religious Law: Christian Religious Laws" by the same author. Portions of the first edition entry appear in the revised version.

Christian religious laws historically comprehend a large spectrum of rules to guide individual conduct and social relationships among the baptized. The laws most likely to have eugenic significance are the canons prohibiting the marriage of relatives. These regulations also form the basis for the modern civil law prohibitions against the marriage of relatives in both the Continental legal systems and the Anglo-Saxon statutory scheme. Though the principal justification given for such prohibitions in Christian law has been ethical and social, there is substantial evidence that they also may reflect considerations classified as eugenic in contemporary scientific research.

The ecclesiastical regulations that forbid marriage between persons closely related by consanguinity are among the most ancient canons of the Christian tradition. Penalties attached to the violation of religious exogamic laws have varied historically in their severity, as, indeed, have the ways of measuring the degrees of kinship and defining within which degrees the crime of incest shall be punished. But the core of the tradition of canon law remains constant and reflects an extreme reluctance to accept the marriages of close relatives as humanly or religiously feasible.

For Roman Catholics all marriages within the direct line of blood relationship, that is, between an ancestor and a descendant by parentage, and within the collateral line to the fourth degree, that is, to third cousins, are forbidden (Code of Canon Law, 1983, canon 1091). The definition of marriages within four degrees of relationship as incestuous dates to the Fourth Lateran Council in 1215 (c. 50). In the Greek Orthodox tradition, marriage in the direct line and in the collateral line to the sixth or seventh degree by the Roman method of computation is prohibited in canon 54 of the Synod in Trullo, 691/692 (Hefele). All Oriental Christians forbid marriages in the direct line; Armenians, Jacobites, and Copts prohibit it in the collateral line to the fourth degree, Melkites to the sixth degree, Serbs and Chaldeans to the third degree, and Ethiopians without distinction. Among Protestant reformers the restrictions of the medieval canon law were accepted by some, such as Phillip Melanchthon and Martin Chemnitz (Kemnitz); only the Old Testament regulations of Leviticus 18:6–18 by others, such as Martin Bucer and, perhaps, Martin Luther; and only the closest ties of direct parental relationship by still others, such as John Wycliffe. In the Anglican community, The Book of Common Prayer contains a table drawn up by Archbishop Matthew Parker based on Leviticus in naming relatives incapable of marriage (Wheatly). Most Protestant churches today follow the prohibitions of civil law regarding incest and kinship marriage (Acte for Kynges Succession; Acte for Succession of Imperyall Crowne; Concerning Precontracte and Degrees).

The sources of and commentaries upon the Christian laws record debate about the extent of the prohibition, the possibility of dispensation within certain close degrees of kinship, and the related question of the divine or natural law origin of the laws (e.g., Burchard of Worms, Decretum, bk. 7, "De Incesto"; Burchard of Worms, Collection in 74 titulis 65.281–284). They reveal, however, only the most sketchy discussion of the foundations of the regulations themselves.

The classical reasons given for the prohibition of consanguineous marriages are ethical and social. The first reason was called the respectus parentelae, namely, that such marriages would undermine the respect due to parents and consequently to all those who are closely related (Aquinas, 1948, Summa theologiae II–II, 154, 9). Second, they constitute a moral danger to family life arising from the possibility of early moral corruption of the young dwelling within the same household in which marriage could be allowed (ibid.; Sánchez 1605, 7.52.12, 7.53). Third, the prohibition of consanguineous marriages prevents the disruption of the family by sexual competition and forces the multiplication of friendships and the spread of charity (Augustine). These three reasons seem to have been sufficient to justify the laws, so that most scholars did not go beyond them to seek a further justification. Adhémar Esmein, for example, said the laws arose out of an instinctive repulsion for incest and were not reflective of any known adverse physical consequences. Some modern authors speculate that the reason for strict enforcement of prohibitions against incestuous marriages was to force the breakup of landed family estates (Duby).

It is only in comparatively modern times that an explicitly eugenic reason for the prohibition has received scientific attention. Writing in 1673, Samuel Dugard noted: "There is a judgment which is said often to accompany these Marriages, and that is Want of Children and a Barrennesse"(p. 53). "The Children are weak, it may be; grow crooked, or, what is worse, do not prove well; presently, Sir, it shall be said what better could be expected? an unlawfull Wedlock must have an unprosperous successe" (p. 51). Ambrosius J. Stapf's Theologia moralis in 1827 alluded to this possibility (p. 359). A fuller treatment is found in Dominic Le Noir's 1873 edition of St. Alphonsus's Theologia moralis. Edward Westermarck in 1889 and Eduard Laurent in 1895 spoke at length of a physiological justification of the canons to prevent indiscriminate inbreeding and the risk of a high incidence of deleterious genetic effects. Franz Wernz, in 1928 (n. 352 [70]), writing from a comprehensive knowledge of the canonical tradition, said the ancient writers also knew of the undesirable effects of excessive inbreeding. He noted reasons derived from contemporary medical science in the writings of Gratian (early twelfth century) (C.xx "Anglis permittitur, ut in quarta vel in quinta generatione cognibitur," c. 20, c. 35, q. 2), Pope Innocent III (1161–1216) (Schroeder), and Thomas Aquinas (Commentum in libros IV Sententiarum, dist. 40 and 41, q. 1, art. 4). Since the late nineteenth century nearly all commentators on the canonical rules speak of eugenic objections to marriages of blood relatives.

It is possible to find in the ancient ecclesiastical commentators an awareness of a eugenic foundation to the prohibition expressed in primitive and undifferentiated modes of speech. For example, a persistent belief was kept alive among theologians and canonists that children of incestuous relationships will die or will be greatly debilitated, or that the familial line will be cursed with sterility. Benedict the Levite (850?) wrote of these marriages: "From these are usually born the blind, the deaf, hunchbacks, the mentally defective, and others afflicted with loathsome infirmities" (Capitularum collectio). Furthermore, in the explanations of the name of the impediment (i.e., the impediment of consanguinity), if one traces their origins through medieval glossography to the Etymologies of Isidore of Seville (560?–636), there appears an awareness of a physiological factor in the blood bond of close relatives that must be weakened before marriage can be contracted safely.

The antecedents of the Christian canons in the Mosaic law (Lev. 18:6–18) and the Roman law (Burge) were taken as expressions of natural law by the canonists and were continued in the barbarian codes (Pactum legis salicae 13.11; Leges visigothae 4.1.1–7; Codex Euriciani 2). In his Ecclesiastical History (I, 27), where the Venerable Bede (673–735) notes these laws, he records a quotation from a letter of Pope Gregory I to Augustine of Canterbury, written in 601 (Responsa Gregorii). The reason given by Gregory for forbidding marriages of close relatives is, "We have learned from experience that from such a marriage offspring cannot grow up." This letter and this reason not only are later picked up and cited by Gratian ("Anglis permittatur," c. 2, c. 35, q. 5) and Thomas Aquinas (Summa theologiae suppl. 54, 3), but may be found in virtually all the canonical collections of the early Middle Ages. Though comment on this passage is rare, comment was, perhaps, unnecessary. The passage from Gregory seems clearly to say that experience teaches that children from forbidden consanguineous marriages are affected or unable to grow up. There is thought to be a physiological consequence to incest. In the light of this it seems probable that the labored argumentation over the question of how close the relationship must be for marriage to be forbidden by natural law must have been conducted in some awareness of a popular belief in the biological consequences of such unions. The fear of genetic anomalies or biological debilitation from indiscriminate inbreeding may not be perfectly articulated. It is difficult to imagine, however, that warning of some physiological dangers to offspring may not have been intended in the frequent citation of Pope Gregory to sustain the severity of the prohibition.

Tomás Sánchez (1605), who wrote the greatest of the canonical commentaries on marriage, says that the most suasive ground for forbidding incestuous unions is that there is a sharing of the blood among close relatives and that the physical image of a progenitor (imago, complexio, effigies, mores, virtus paterna) passes to offspring, so that the blood must be weakened through successive generations before marriage should be contracted (7.50; 7.51.1–2). Thus, preventing marriages of close relatives to protect the offspring by allowing several generations to pass before procreation can be called a measure of eugenic foresight, however simple the scientific awareness to support it may have been.

In summary, a eugenic foundation to Christian religious laws forbidding the marriage of close relatives is clearly articulated and commented upon by modern scholars from the late eighteenth and nineteenth centuries. Evidence of this kind of awareness may be discovered earlier in the canonical sources, however, going back at least to the seventh century. It would seem consistent with the eugenic connotation of those laws rooted in antiquity, together with a Christian sense of responsibility for offspring that partly motivated them, to consider further eugenic restrictions on marriage in Christian communities today, in light of contemporary knowledge of genetics.

william w. bassett (1995)

SEE ALSO: Christianity, Bioethics in; Eugenics; Genetic Discrimination; Genetic Engineering, Human; Genetic Testing and Screening; Human Dignity; Human Rights; Population Ethics, Religious Traditions: Protestant Perspectives;Population Ethics, Religious Traditions: Roman Catholic Perspectives; and other Eugenics and Religious Law subentries


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Eugenics and Religious Law: II. Christianity

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