Short answers, pulled from the story.
Emperor Trajan assumed power through adoption by his predecessor Nerva. This practice enabled peaceful transitions of political authority and created male heirs to manage vast estates.
The Commonwealth of Massachusetts enacted the first modern adoption law in 1851. This legislation codified the ideal of the best interests of the child for the first time in history.
An estimated 200,000 children traveled from urban centers to rural regions under this program. Most children were indentured rather than legally adopted to families who took them in.
Adoption became the obvious solution for infertile couples during the period from 1945 to 1974 because illegitimate births rose three-fold after World War II as sexual mores changed rapidly. Many mothers were forced or coerced into relinquishing their children during these years.
The Hague Adoption Convention has been ratified by 105 countries since it came into force on the 1st of May 1995. It governs international adoption involving placing a child outside their country of birth through public or private agencies.