Paternity, Research on

PATERNITY, Research on. - While from the ethical point of view the search for paternity may be considered in itself and by itself lawful, various civil codes, for reasons of expediency, do not permit investigations into paternity except in cases exhaustively provided for. This prohibition originates in the French revolutionary laws, from which it passed into the Napoleonic Code.

Article 269 of the Italian Civil Code permits the judicial declaration of paternity: 1) when the mother and the alleged father have notoriously lived together as spouses at the time to which conception dates back; 2) when paternity results indirectly from a civil or criminal judgment or from an unequivocal written declaration of the person to whom it is attributed; 3) when there has been abduction or carnal violence at the time corresponding to that of conception; 4) when there is possession of the status of natural child (v. PROLE).

In some civilized countries the problem of the search for paternity is assuming new aspects (in the United States of America there exist legally recognized societies authorized to summon the alleged father to court), and the biological sciences are proceeding in their studies in order to establish the principles on which to base proof of paternity; special mention is due to the biological proof of blood groups.

In human blood there exist two agglutinogens called agglutinogen A and agglutinogen B, bound to the red blood cells. The blood serum, in turn, contains two agglutinins, α and β. They have been divided into four blood groups: group I: it possesses no agglutinogens while it possesses the two agglutinins; it is group O, or that of universal donors; group II: it is group A, provided with agglutinogen A and agglutinin β or anti-B; group III: it possesses agglutinogen B and agglutinin α or anti-A; group IV: (AB) which contains both agglutinogens and lacks agglutinins; it is the group of universal recipients. When a blood containing a given agglutinogen is brought into contact with another blood containing the corresponding agglutinin, the phenomenon of isoagglutination occurs: the red blood cells are agglutinated and under the microscope irregular clumps of them are observed. In practice the blood group test is carried out by means of test sera. The individual blood group is a constant, congenital character, inherited from the parents according to Mendelian laws. It undergoes no qualitative alteration during life; at birth there is an incomplete quantitative development of the agglutinogens, which possess a reception strength of about a 4th, an 8th, compared with that of the adult; this strength increases until it reaches its maximum around 15-20 years of age and remains so until advanced age. For this reason errors of group determination can occur in newborns and infants.

Important is knowledge of the following laws: 1) the properties A and B are dominant characters with respect to O, so that they are found in the children only when they are also present in the parents; however, even when present in the parents, they may not appear in the children; the property O, on the other hand, which is recessive, can be found in the children even if it does not manifest itself in the parents; 2) parents belonging to group O cannot have children of group AB; parents belonging to group AB cannot have children belonging to group O. Landsteiner and Levine in 1927 brought to light new agglutinogens, besides agglutinogens A and B, to which no preformed agglutinins correspond in the blood of other individuals; these are the blood groups called respectively M, N, MN. Subsequently agglutinogen P was also found, and in 1940 Landsteiner and Wiener rediscovered agglutinogen Rh, present in about 85% of men, who are thus assigned to the Rh-positive group, while 15% belong to the Rh-negative group. From these findings two other laws have arisen: 1) the properties M and N are dominant properties and cannot appear in the children if the parents lack them; 2) the properties M and N are allelomorphic properties: for this reason the property M (without N) or the property N (without M) must appear in the children if they are present singly in the parents, when they are found in the pure state. By investigating the blood groups present in the blood of the mother, of the child and of the alleged father and comparing them with the data of appropriate tables, one can arrive at the exclusion of paternity. In practice, to group compatibility no value is given as a real relationship of filiation, whereas on the contrary in cases of incompatibility the exclusion of the alleged father can be affirmed with certainty.

In recent times further research has been done on group-specific systems, especially by foreign authors. The various subgroups of A, namely A₁, A₂, A₃, etc., have been the object of study, and importance has been given to them not only qualitatively but also quantitatively, just as importance has been given to the notable rarity of the subtypes A₃, A₁, A₂, A₃, N₂, N₃. For example, the ascertainment of an A₄ in the alleged father and in the child, which is found with a probability of one in a million, led Hirszfeld and Amsel to consider paternity established. The same may be said of the importance given to the rarity of certain genotypes of the Rh system, of the rarity of the Leway factor, Celano, etc.

In Italy too, research has been done and is in progress, although limited by the difficulty of obtaining the necessary sera. According to recent research, at present the probabilities of excluding paternity in the various mother-child combinations reach, for Italians, up to 90.8%, for the principal properties A B O, MN, Rh alone. Greater probabilities are obtained if the investigation is extended to the P system, to N and to the principal subtypes of Rh.

The importance of these group-specific researches for resolving, from the biological point of view, the much-discussed problem of the search for paternity cannot therefore be disregarded.

Maria De Arcangelis