Final answer:
Unilineal descent exists in three major forms: patrilineal descent, which follows the father's line; matrilineal descent, which follows the mother's line; and ambilineal descent, where lineage can be chosen through either parent's line based on varying circumstances.
Step-by-step explanation:
In unilineal descent systems, kinship is traced through a single gender line. This system is adhered to as a social norm in various societies and comes in three major forms:
- Patrilineal descent: This type of descent follows the father's line only. Both males and females trace their lineage through male ancestors. For example, in patrilineal societies like rural China and India, males carry on the family surname. Males are seen as permanent members of their family lineage, whereas females are considered temporary members before they marry and join their husband's lineage.
- Matrilineal descent: In this system, the lineage is traced through the mother's line only. Unlike patrilineal descent, both males and females trace their descent exclusively through female ancestors. Males will have their mother's matrilineal descent, and females will pass on the descent through their children.
- Ambilineal descent: Ambilineal or cognatic descent allows for the lineage to be traced through either the father's or the mother's line. This choice can be made by each family, often based on marriage alliances or the relative advantages offered by one side or the other. Each child within the same family may have their kinship traced through a different parent.
It is worth noticing that many modernized nations practice a bilateral descent system, where lineage is traced through both the mother's and father's sides.