There are so many different social traditions and kinship structures in existence, that it would be impossible to discuss a single model of social organization that occurs through all periods and cultures. Nor can one avoid the problem by searching for some singular and universal ideals, because the ideals of kinship structures also vary across periods and cultures. The nuclear family as we know it in 21st century western culture is a relatively recent phenomenon, and not one readily universalizable. Even the notion that a family consists of people held together by love, rather than practical purposes of procreation and child rearing is a relatively recent cultural phenomenon limited in geographic and chronological range. Instead, it would be more accurate to say that different societies have a wide range of successful kinship structures and family ideals.