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.
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.
Cars extended the range of dating as well as enabled back-seat sexual exploration.
There are considerable differences between social and personal values.
These people will have dates on a regular basis, and they may or may not be having sexual relations.
This period of courtship is sometimes seen as a precursor to engagement.
New types of relationships formed; it was possible for people to live together without marrying and without children.
Information about human sexuality grew, and with it an acceptance of all types of sexual orientations is becoming more common.
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.