Have you met Karli? Her mom struggles with substance abuse, and she is in foster care. Karli is not a real child…she’s a six-year-old Muppet with yellow pigtails made of ostrich feathers. The creators of Sesame Street introduced her on the show last month. They did it because more than 400,000 children are in foster care in this country, and it is estimated that nearly 80% of those cases involve substance abuse.
As the idea of institutional care gained acceptance, formal rules appeared about how to place children into families: boys could become apprenticed to an artisan and girls might be married off under the institution's authority.[19] Institutions informally adopted out children as well, a mechanism treated as a way to obtain cheap labor, demonstrated by the fact that when the adopted died, their bodies were returned by the family to the institution for burial.[20]

United States approx 136,000 (2008)[69] 3,978,500 (2015)[70] ≈3 per 100 live births The number of adoptions is reported to be constant since 1987. Since 2000, adoption by type has generally been approximately 15% international adoptions, 40% from government agencies responsible for child welfare, and 45% other, such as voluntary adoptions through private adoption agencies or by stepparents and other family members.[69]
Similar mechanisms appear to be at work in the physical development of adoptees. Danish and American researchers conducting studies on the genetic contribution to body mass index found correlations between an adoptee's weight class and his biological parents' BMI while finding no relationship with the adoptive family environment. Moreover, about one-half of inter-individual differences were due to individual non-shared influences.[115][116]

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.

Markedly different from the modern period, ancient adoption practices put emphasis on the political and economic interests of the adopter,[4] providing a legal tool that strengthened political ties between wealthy families and created male heirs to manage estates.[5][6] The use of adoption by the aristocracy is well documented; many of Rome's emperors were adopted sons.[6] Adrogation was a kind of Roman adoption which required the adrogator to be at least 60 years old.
By 1979, representatives of 32 organizations from 33 states, Canada and Mexico gathered in Washington, DC to establish the American Adoption Congress (AAC) passing a unanimous resolution: "Open Records complete with all identifying information for all members of the adoption triad, birthparents, adoptive parents and adoptee at the adoptee's age of majority (18 or 19, depending on state) or earlier if all members of the triad agree."[161] Later years saw the evolution of more militant organizations such as Bastard Nation (founded in 1996), groups that helped overturn sealed records in Alabama, Delaware, New Hampshire, Oregon, Tennessee, and Maine.[162][163] Simultaneously, groups such as Origins USA (founded in 1997) started to actively speak about family preservation and the rights of mothers.[164] The intellectual tone of these recent reform movements was influenced by the publishing of The Primal Wound by Nancy Verrier. "Primal wound" is described as the "devastation which the infant feels because of separation from its birth mother. It is the deep and consequential feeling of abandonment which the baby adoptee feels after the adoption and which may continue for the rest of his life."[153]
Adoptions can occur either between related family members, or unrelated individuals. Historically, most adoptions occurred within a family. The most recent data from the U.S. indicates about half of adoptions are currently between related individuals.[78] A common example of this is a "stepparent adoption", where the new partner of a parent may legally adopt a child from the parent's previous relationship. Intra-family adoption can also occur through surrender, as a result of parental death, or when the child cannot otherwise be cared for and a family member agrees to take over.
The research says that the dysfunction, untruths and evasiveness that can be present in adoptive families not only makes identity formation impossible, but also directly works against it. What effect on identity formation is present if the adoptee knows they are adopted but has no information about their biological parents? Silverstein and Kaplan's research states that adoptees lacking medical, genetic, religious, and historical information are plagued by questions such as "Who am I?" "Why was I born?" "What is my purpose?" This lack of identity may lead adoptees, particularly in adolescent years, to seek out ways to belong in a more extreme fashion than many of their non-adopted peers. Adolescent adoptees are overrepresented among those who join sub-cultures, run away, become pregnant, or totally reject their families.[133][134]

Psychologists' findings regarding the importance of early mother-infant bonding created some concern about whether parents who adopt older infants or toddlers after birth have missed some crucial period for the child's development. However, research on The Mental and Social Life of Babies suggested that the "parent-infant system," rather than a bond between biologically related individuals, is an evolved fit between innate behavior patterns of all human infants and equally evolved responses of human adults to those infant behaviors. Thus nature "ensures some initial flexibility with respect to the particular adults who take on the parental role."[96]