Ancestor: definition, types, genetics, legal and cultural significance

In all social groups and societies, cultural rules of descent determine whether only one parent's lineage or the lines of both parents are counted as a person's ancestors, and the extent to which collateral relatives and adopted or recognized relatives are also recognized as ancestors.

The closest social construct of descent is the "male line", especially in noble families: In them, the lineage restricts the ancestors of a person to his forefathers, to whom only legitimate sons of the respective forefather are counted in each generation, the so-called agnates. The order of birth of sons may play a special role in the succession (see primogeniture, firstborn, primogeniture). In contrast, some 160 ethnic groups and indigenous peoples restrict their ancestry to their maternal line only. In contrast to these unilineal rules of descent, the European cultural area applies the equal descent of father and mother (cognatic-bilateral), as in most highly industrialized societies; this rule is also followed by nearly 30 percent of the world's 1300 ethnic peoples. The reference to the ancestors of both lines, however, leads to the fact that one cannot remember very many generations and the number of side relatives becomes very large; in contrast, members of a culture with pure maternal or paternal lines can name up to ten or more generations of their ancestors.

Another difference to biological ancestry are side lines of siblings of parents and forefathers, which are often counted together with their respective descendants as ancestors of a person; side-line ancestors are for example uncles (brothers of parents) and great-aunts (daughters of siblings of great-grandparents). However, in the oral or written transmission of ancestral generations, entire side lines may have been suppressed, if, for example, an ancestor was disowned by his (extended) family due to illegitimacy or quarrel, or as a "black sheep" and subsequently disowned - together with his descendants.

The third difference to genetic ancestors is formed by legal conceptions, which make it possible to include persons in one's own ancestry who are or were not related by blood to other ancestors by means of adoption or acknowledgement of paternity.

In genealogy (family history research), a person's ancestors known by name, including living ones, are presented in a "genealogical list" or "genealogical chart": Both parents' parents are the four grandparents, all their siblings are the great-uncles and -aunts, their parents are the eight great-grandparents, and so on in ascending order (see kinship and generation names). The representation may be limited to all paternal and maternal forefathers (also common in animal breeding), or may also include lateral lines of siblings of parents and forefathers generations (see also the "Family Tree").

A "Spitzenahn" is either a progenitor (ancestor) or a progenitor (ancestress), or the oldest verifiable ancestor as the earliest documented ancestor of a person.

In modern genealogy, maternal and paternal ancestors are of equal importance. Thereby often an ancestor is found in distant collateral lines, who is also included in the ancestral list of another (known) person; such a distant relationship is called "ancestral community" (in contrast to the "community of ancestors" in ancestor worship). Full-blooded siblings have a complete, congruent community of ancestors because of their identical ancestors.

Some ancestors may occupy two positions on the ancestral list at the same time, for example, cousin marriages result in two grandparents occupying four ancestral positions at once for their descendants as parents of the cousin parents, and these overlaps continue backwards; this effect is called "ancestor shrinkage": The mathematically possible number of ancestors dwindles down to a smaller number of actual ancestors; an "ancestor loss" results.

Step-ancestors" are (later) spouses of ancestors of a person from whom he or she is not descended, for example a stepfather or a later wife of the grandfather (step-grandmother); there is no kinship to them, but a relationship of affinity by marriage, which in more recent times also includes the registered partners of ancestors.