Patrilineality

Patrilineality (a.k.a. agnatic kinship) is a system in which one belongs to one's father's lineage; it generally involves the of property, names or titles through the  line as well.

A patriline is a line of descent from a male to a  (of either ) in which the individuals in all intervening generations are. In a patrilineal (= agnatic descent), an individual is considered to belong to the same  as his or her father. This is in contrast to the less common pattern of.

The agnatic ancestry of an individual is that person's pure male ancestry. An agnate is one's genetic relative exclusively through males: a kinsman with whom one has a common ancestor by descent in unbroken male line.

In cultural, a patrilineage (or patriclan) is a male and female kin group each of whom is related to the common  through male forebears.

Contrary to popular belief, one's agnate may be male or female, provided that the kinship is calculated patrilineally, i.e., only through male ancestors. Traditionally, this concept is applied in determining the names and membership of European. For instance, because Queen was married to a prince of, her son and successor, , was a member of that dynasty, and is considered the first British king of the House of Saxe-Coburg-Gotha. (And so, technically, are his descendants in the male line; see .) But Victoria is reckoned to have belonged to her father's House of, despite her marriage and the fact that by marriage she legally became a member of the Saxon dynasty and acquired the name of that family. Agnatically, she was a Hanover, and is considered the last member of that dynasty to reign over Britain.

In medieval and later, the was purported to be the grounds for only males being able for hereditary succession to monarchies and fiefs, i.e., in patrilineal or agnatic succession.

Genetic genealogy
The fact that the (Y-DNA) is paternally inherited enables patrilines, and agnatic kinships, of men to be traced through genetic analysis.

(Y-mrca) is the patrilineal human, from whom all Y-DNA in living men is descended. Y-chromosomal Adam probably lived between 60,000 and 90,000 years ago, judging from and  studies.

Early medical theories
In ancient medicine there was a dispute between the one-seed theory, expounded by, and the two-seed theory of. By the one-seed theory, the germ of every embryo is contained entirely in the male seed, and the role of the mother is simply as an incubator and provider of food: on this view only a patrilineal relative is genetically related. By the two-seed theory, the embryo is not conceived unless the male and female seed meet: this implies a bilineal, or cognatic, theory of relationship. It may be significant that Galen lived at about the same time that Roman law changed from the agnate to the cognate system of relationships.

Common to both theories was the mistaken belief that the female emits seed only when she comes to orgasm. Given that assumption, the evidence for the one-seed theory is the fact that a woman can conceive without coming to orgasm (though this was still a matter of dispute in the ancient world and the Middle Ages ). The evidence for the two-seed theory is the fact that a person can look like his or her maternal relatives. These two facts could not be reconciled until the discovery of.

Roman law
The terms "agnate" (for patrilineal relatives) and "cognate" (for all relatives equally) are taken from. In Roman times, all citizens were divided by gens (clan) and familia (sept), determined on a purely patrilineal basis, in the same way as the modern inheritance of surnames. (The gens was the larger unit, and was divided into several familiae: a person called "Gaius Iulius Caesar" belonged to the Julian gens and the Caesar family.)

In the early Republic, inheritance could only occur within the family, and was therefore purely agnatic. In Imperial times, this was changed by the Praetorian edict, giving paternal and maternal relatives equal rights.

In the Bible
The line of descent for monarchs and main personalities is almost exclusively through the main male personalities. Tribal descent, such as whether one is a or a, is still inherited patrilineally in Judaism, as is communal identity as a  or. This contrasts with the rule for inheritance of Jewish status in, which is matrilineal. See and.