There are an estimated 16.2 million documented orphans worldwide, with as many as 100 million more children living on the streets. It’s a problem of crisis proportions, which makes it perhaps strange that so many of us consider adoption as more of a last resort than a first-order obligation – to be considered only if the path to having genetically-related children is blocked. This week we’re looking at the justifications for genetic preference in families, and asking how these justifications stack up against the moral duty to adopt.