Thus, the concept of marriage is changing widely in many countries.
Historically, marriages in most societies were arranged by parents and older relatives with the goal not being love but legacy and "economic stability and political alliances", according to anthropologists.
However, one particularity of the human species is that pair bonds are often formed without necessarily having the intention of reproduction.
In modern times, emphasis on the institution of marriage, generally described as a male-female bond, has obscured pair bonds formed by same-sex and transsexual couples, and that many heterosexual couples also bond for life without offspring, or that often pairs that do have offspring separate.
From about 1700 a worldwide movement perhaps described as the "empowerment of the individual" took hold, leading towards greater emancipation of women and equality of individuals.
Men and women became more equal politically, financially, and socially in many nations.
As humans societies have evolved from hunter-gatherers into civilized societies, there have been substantial changes in relations between people, with perhaps one of a few remaining biological constants being that both adult women and men must have sexual intercourse for human procreation to happen.