Some Scandinavian countries extended benefits and obligations to same-sex couples by means of a registered domestic partnership or civil union, both of which terms meant different things in different contexts. This imposes increased duties on human parents for the care of their children, and marriage traditionally has been seen as the institution best suited to fulfill these parental duties and responsibilities.
In most societies marriage also established the permissible social relations allowed to the offspring, including the acceptable selection of future spouses.Belgium passed a similar law in 2003, except that it limited marriageable partners to those whose national laws allowed such marriages (i.e., Belgians could only marry Belgians or Netherlanders). In the biological evolutionary scale, the more complex the species, the longer the offspring is dependent on its mother for survival from the time of birth to maturity.Court decisions in some Canadian provinces made same-sex marriages legal there in 2002–04. Human beings, at the top of the evolutionary scale, require the most time of all species to reach maturity.Endogamy, the practice of marrying someone from within one’s own tribe or group, is the oldest social regulation of marriage.When the forms of communication with outside groups are limited, endogamous marriage is a natural consequence.