Consanguinity refers to the biological or genetic relationship of people based on their descent from one another or from a common ancestor , in technical terms consanguinity ( Latin consanguinitas : con "together, with", and sanguis " blood ") - in contrast to legal relationships (through adoption , acknowledgment of paternity or surrogate ) or by marriage affinity ( affinity relationship). An alleged blood-related parentage does not always have to correspond to the facts, especially with regard to paternity (see cuckoo children and lack of proof of paternity ), only modern parentage reports enable biological unambiguity (see biological parenthood ).
Consanguinity plays a major role, especially in marriage law , since in most cultures marriages between close blood relatives are considered inadmissible ( prohibition of incest with regard to possible offspring ).
In “first degree” blood relatives ( parents of children ), half of the genes are identical due to direct descent. In the case of “second degree” genetic relatives ( grandparents to grandchildren , siblings to each other), on average a quarter of the genes come from a common ancestor. The genetic degree of kinship is calculated in the same way as the legal degree of kinship , and similar to the kinship coefficient : The shortest kinship path (without loss of ancestry ) between two people is sought and the number of procreations that took place in total is determined. Alternatively, the total of the people involved in this route (including starting point and destination) can be formed. If the reference person ( test person ) is subtracted from this, the result is the same as with the first method.
For a long time a person's blood-related descent was decisive for citizenship in Germany (principle of descent : Jus sanguinis ); Since 2000, the place of birth or territorial principle (Jus soli) has also been applied in the so-called option model (for the Nazi era see also Deutschblütig ).
Catholic marriage law
In Catholic canon law , consanguinity is not only an obstacle to marriage in a straight line (parents-children, grandparents-grandchildren) , but also in the sideline up to the fourth degree (siblings are second degree blood relatives , uncle / niece or aunt / nephew are third blood relatives 1st degree cousins are fourth degree relatives ). It is controversial among canon lawyers in which cases this impediment to marriage is divine law (i.e. derived directly from the order of creation) and when purely church law. Therefore the code of law in it from this obstacle in the straight line (direct pre- / descendants no exemption) and in the second degree of the collateral line (siblings) ( dispensation admit).
The term consanguinity originated long before deoxyribonucleic acid was identified as the carrier of genetic information in the 20th century . According to the 23rd edition of the Etymological Dictionary of the German Language , the “blood” in consanguinity stands for a liquid body “necessary for the reproduction of its sex”. It was based on the idea that the fluids that create new life are “eliminated from the blood”.
- Lukas, Schindler, Stockinger: blood relatives. In: Online Interactive Glossary: Marriage, Marriage, and Family. Institute for Cultural and Social Anthropology, University of Vienna, 1997 (detailed notes, with references).