Adoption in ancient Rome was primarily a legal procedure for transferring paternal power (potestas) to ensure succession in the male line within Roman patriarchal society.
The Latin word adoptio refers broadly to "adoption", which was of two kinds: the transferral of potestas over a free person from one head of household to another; and adrogatio, when the adoptee had been acting sui iuris as a legal adult but assumed the status of unemancipated son for purposes of inheritance.
In contrast to modern adoption, Roman adoptio was neither designed nor intended to build emotionally satisfying families and support childrearing.
[1] Nor was marriage required; an adult bachelor could adopt in order to pass along his family name and potestas,[12] as could a citizen eunuch (Latin spado).
[26] Legislation that more closely regulated the varied statuses of liberti left the adoptee as a freedman who could not, for example, marry into the senatorial order even if he was adopted by a senator.
[24] In the late Republican era, Publius Clodius Pulcher famously subverted the usual course of "adopting up", surrendering his patrician status and becoming a nominal plebeian in order to qualify for the office of tribune.
[29] Around the same time, a nominal adoption allowed Publius Cornelius Lentulus Spinther, son of the consul of 57 BC, to take a place in the College of Augurs by getting around the rule against having two members from the same gens.
[32] The restrictions under the decree are not preserved in full, but a request for adrogatio could be denied if the would-be adoptive father already had children or was under the age of sixty and assumed able to procreate.
[33] Adoptio had some commonalities with emancipatio, the procedure by which an adult son was released from paternal potestas – regardless of age, Roman men and women remained in effect legal minors as long as their father was alive unless emancipated.
When Tiberius was adopted in adulthood by Augustus, he thereafter observed this longstanding legal requirement by crediting any property he received through inheritance to the peculium rather than his private ownership.
[37] The development of adrogatio as a form of adoption is bound up with an early procedure for making a will that required the approval of the comitia calata, an assembly of the Roman people.
[34] Because adoption law developed to support the particular institutions of Roman society, adrogatio could take place only in the city of Rome until the reign of Diocletian in the late third century.
[42] Although adoptio was a practice aimed at furthering the succession of male privileges, both men and women could in effect "adopt" by passing along their property in a will with the condition that the heir carry on the family name (condicio nominis ferendi).
From the late Republic through the Principate, most Roman women married sine manu, meaning that they remained part of their birth family and did not submit to their husband's potestas.
[50] Provisions for retroactive legitimation became more capacious in late antiquity as family law was adapted during the Christianization of the Roman Empire, in particular under Constantine and Justinian.
However, the quasi-marital union of contubernium was available to heterosexual slave couples with the owner's approval, and expressed an intent to marry if both parties gained rights of marriage and succession upon manumission.
[51][54] Many Roman emperors came to power through adoption, either because their predecessors had no natural sons, or simply to ensure a smooth transition for the most capable[citation needed] candidate.
Adoption never became the official method of designating a successor, in part because Roman identity was based on citizenship with a visceral rejection of hereditary kingship.
Augustus's early intentions seem to have been to apprentice and promote a successor on the basis of merit, but his longevity instead created an apparatus of centralized power from which his status as a private citizen could no longer be extricated.
His fashioning of himself as "father of his country" enabled the transferral of his power over the Roman people in the same way that a paterfamilias of a family estate was bound to transfer his potestas whether or not the available successor was fully meritorious.