When considering one’s lineage, most people in the United States look to both their father’s and mother’s sides. Both paternal and maternal ancestors are considered part of one’s family. This pattern of tracing kinship is called bilateral descent. Note that kinship, or one’s traceable ancestry, can be based on blood or marriage or adoption. Sixty percent of societies, mostly modernized nations, follow a bilateral descent pattern. Unilateral descent (the tracing of kinship through one parent only) is practiced in the other 40 percent of the world’s societies, with high concentration in pastoral cultures .
There are three types of unilateral descent: patrilineal, which follows the father’s line only; matrilineal, which follows the mother’s side only; and ambilineal, which follows either the father’s only or the mother’s side only, depending on the situation. In patrilineal societies, such as those in rural China and India, only males carry on the family surname. This gives males the prestige of permanent family membership while females are seen as only temporary members. U.S. society assumes some aspects of patrilineal decent. For instance, most children assume their father’s last name even if the mother retains her birth name.