Inheritance of acquired traits

Inheritance is the practice of passing on property, titles, debts, and obligations upon the death of an individual. It has long played an extremely important role in human societies.

Both anthropology and sociology have made detailed studies in this area. Many cultures feature patrilineal succession, also known as gavelkind, where only male children can inherit. Some cultures also employ matrilineal succession only passing property along the female line. Even more radical than the patrilineal succession is the practice of primogeniture, under which all property goes to the eldest child, or often the eldest son (the first-born). Conversely there are also systems where everything is left to the youngest child. Some ancient societies and most modern states employ partible inheritance, under which every child inherits (usually equally). There was also mixed systems: Many states have inheritance taxes, under which a portion of any estate goes to the government, though the government technically is not an heir.
 * in Swedish culture beginning from 13th century and up until 19th century, a son inherited twice as much as his sister. This rule was introduced by the Regent Birger Jarl, and it was regarded as an improvement in its era, since daughters were previously usually left without.
 * among ancient Israelites, the eldest son received twice as much as the other sons.

Employing differing forms of succession can effect many areas of society. Gender roles are profoundly affected by inheritance laws and traditions. Primogeniture has the effect of keeping large estates united and thus perpetuating an elite. With partible inheritance large estates are slowly divided among many descendants and great wealth is thus diluted, leaving higher opportunities to individuals to make a success. (If great wealth is not diluted, the positions in society tend to be much more fixed and opportunities to make an individual success are lower.)

Inheritance can be organized in a way that its use is restricted by the desires of someone (usually of the decedent). An inheritance may have been organized as a fideicommission, which usually cannot be sold or diminished, only its profits are disposable. A fideicommission's succession can also be ordered in a way that determines it long (or eternally) also with regard to persons born long after the original decedent. Cf also trust. Royal succession has typically been more or less a fideicommission, the realm not (easily) to be sold and the rules of succession not to be (easily) altered by a holder (a monarch).

In more archaic days, particularly the possession of inherited land has been much more like a family trust than a property of an individual. Yet quite recently in many European countries, sale of the whole of or a significant portion of a farm required consent from certain heirs, and/or heirs had the intervening right to obtain the land in question with same sales conditions as in the sales agreement in question.

In common law jurisdictions an heir is a person who is entitled to receive a share of the decedent's property via the rules of inheritance in the jurisdiction where the decedent died or owned property at the time of his death. Strictly speaking, one only becomes an heir upon the death of the related person: it was improper to speak of the "heir" of a living person since the exact identity of the persons entitled to inherit would not be determined until the time of death. However, it is not totally wrong to speak about "heir" during the lifetime of the decedent at least in cases where the heir has such a position that only her/his own demise before, may prevent becoming a heir at the death (for example, if the birth of another person cannot take away the position as a heir) - this is a heir apparent.