Sir Henry Maine tells us that adoption is one of the oldest and most widely employed of legal fictions. Without it, he asserts, society would scarcely have escaped its swaddling clothes. It commanded the approval of the greater number of archaic societies and has proven to be the most perdurable of all artificial relationships designed to prolong the continuity of family existence.
The family is the basic group of most primitive societies. Those who were related by blood naturally gravitated to each other to form this first ring of society's organization. In the same way successively higher organizational units were also predicated on blood relationship between the members, e.g., the house, the tribe and finally the state. Not every early society was actually formed by descent from the same ancestor but all those which achieved permanence were so descended or were assumed to be. This assumption was nearly always false since everywhere men of alien descent were admitted into families other than their own. The Greek states, Rome, the Teutonic aristocracies, the Celtic clan associations, the Slavonic Russians and Poles all practiced adoption.
Leo A. Huard,
The Law of Adoption: Ancient and Modern,
9 Vanderbilt Law Review
Available at: https://scholarship.law.vanderbilt.edu/vlr/vol9/iss4/6