Adoption was a very important part of traditional society in nearly every Native American tribe. Because of the highly structured clan system in most Native American societies, it was rare for an orphaned child to be left without a family– usually there were very clear clan rules about who inherited the responsibility for a child whose parents had died. It was not even considered “adoption” in most tribes for a child to be taken in by a maternal uncle or another relative or clan member. Some tribes had traditional practices of adopting people outside of their tribe, it was considered a major moral principle that outsiders adopted into the tribe must be treated as family.
You are correct in understanding that colonization impacted these practices. Some tribes currently still engage in the practice of adoption and adoption rituals. Each tribe is a sovereign nation and each tribe makes decisions upon who can and cannot become tribal citizens. This practice is influenced by the United States government, I am unaware of the United States acknowledging “adopted” citizens as members of Federally recognized tribes.
If you are a descendent of a Tribal Nation, were adopted outside of your tribe, and are seeking information about becoming a tribal citizen, I would suggest contacting your tribe directly to find out what the process of enrollment is. Many tribes have a “enrollment” department with staff dedicated to helping you through the process of tribal enrollment.
If you are not aware of your tribal connection, or if you are unable to become enrolled in a tribe, being Native American means different things to different people. We are a diverse and beautiful community. I would suggest finding a connection to the Native American community in your area and make connections to that community.
Good luck on your journey,