Unlike guardianship or other systems designed for the care of the young, adoption is intended to effect a permanent change in status and as such requires societal recognition, either through legal or religious sanction. Historically, some societies have enacted specific laws governing adoption; where others have tried to achieve adoption through less formal means, notably via contracts that specified inheritance rights and parental responsibilities without an accompanying transfer of filiation. Modern systems of adoption, arising in the 20th century, tend to be governed by comprehensive statutes and regulations.

Concerning developmental milestones, studies from the Colorado Adoption Project examined genetic influences on adoptee maturation, concluding that cognitive abilities of adoptees reflect those of their adoptive parents in early childhood but show little similarity by adolescence, resembling instead those of their biological parents and to the same extent as peers in non-adoptive families.[114]
In sum, reunions can bring a variety of issues for adoptees and parents. Nevertheless, most reunion results appear to be positive. In the largest study to date (based on the responses of 1,007 adoptees and relinquishing parents), 90% responded that reunion was a beneficial experience. This does not, however, imply ongoing relationships were formed between adoptee and parent nor that this was the goal.[170]

Europe's cultural makeover marked a period of significant innovation for adoption. Without support from the nobility, the practice gradually shifted toward abandoned children. Abandonment levels rose with the fall of the empire and many of the foundlings were left on the doorstep of the Church.[18] Initially, the clergy reacted by drafting rules to govern the exposing, selling, and rearing of abandoned children. The Church's innovation, however, was the practice of oblation, whereby children were dedicated to lay life within monastic institutions and reared within a monastery. This created the first system in European history in which abandoned children did not have legal, social, or moral disadvantages. As a result, many of Europe's abandoned and orphaned children became alumni of the Church, which in turn took the role of adopter. Oblation marks the beginning of a shift toward institutionalization, eventually bringing about the establishment of the foundling hospital and orphanage.[18]


Private domestic adoptions: under this arrangement, charities and for-profit organizations act as intermediaries, bringing together prospective adoptive parents and families who want to place a child, all parties being residents of the same country. Alternatively, prospective adoptive parents sometimes avoid intermediaries and connect with women directly, often with a written contract; this is not permitted in some jurisdictions. Private domestic adoption accounts for a significant portion of all adoptions; in the United States, for example, nearly 45% of adoptions are estimated to have been arranged privately.[83]

Europe's cultural makeover marked a period of significant innovation for adoption. Without support from the nobility, the practice gradually shifted toward abandoned children. Abandonment levels rose with the fall of the empire and many of the foundlings were left on the doorstep of the Church.[18] Initially, the clergy reacted by drafting rules to govern the exposing, selling, and rearing of abandoned children. The Church's innovation, however, was the practice of oblation, whereby children were dedicated to lay life within monastic institutions and reared within a monastery. This created the first system in European history in which abandoned children did not have legal, social, or moral disadvantages. As a result, many of Europe's abandoned and orphaned children became alumni of the Church, which in turn took the role of adopter. Oblation marks the beginning of a shift toward institutionalization, eventually bringing about the establishment of the foundling hospital and orphanage.[18]
The biological relationship between a parent and child is important, and the separation of the two has led to concerns about adoption. The traditional view of adoptive parenting received empirical support from a Princeton University study of 6,000 adoptive, step, and foster families in the United States and South Africa from 1968 to 1985; the study indicated that food expenditures in households with mothers of non-biological children (when controlled for income, household size, hours worked, age, etc.) were significantly less for adoptees; step-children, and foster children, causing the researchers to speculate that, instinctively, people are less interested in sustaining the genetic lines of others.[92] This theory is supported in another more qualitative study where in adoptive relationships marked by sameness in likes, personality, and appearance, both adult adoptees and adoptive parents report being happier with the adoption.[93]
Ad hoc studies, performed in the U.S., however, suggest that between 10 and 25 percent of adoptions through the child welfare system (e.g., excluding babies adopted from other countries or stepparents adopting their stepchildren) disrupt before they are legally finalized and from 1 to 10 percent are dissolved after legal finalization. The wide range of values reflects the paucity of information on the subject and demographic factors such as age; it is known that teenagers are more prone to having their adoptions disrupted than young children.[91]
Unlike guardianship or other systems designed for the care of the young, adoption is intended to effect a permanent change in status and as such requires societal recognition, either through legal or religious sanction. Historically, some societies have enacted specific laws governing adoption; where others have tried to achieve adoption through less formal means, notably via contracts that specified inheritance rights and parental responsibilities without an accompanying transfer of filiation. Modern systems of adoption, arising in the 20th century, tend to be governed by comprehensive statutes and regulations.
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