Final answer:
The two primary cognatic descent systems are ambilineal descent, where kinship is traced through either the mother's or the father's line, and bilateral descent, where it is traced through both parents' lines. Bilateral descent is more inclusive, acknowledging both parental lineages, while ambilineal descent provides familial flexibility in choosing lineage.
Step-by-step explanation:
The two major types of cognatic descent systems are ambilineal descent and bilateral descent. In ambilineal descent, an individual's kinship can be traced through either the mother's or the father's line, depending on various familial factors, such as economic opportunities or cultural preferences. This allows families the flexibility to choose the lineage that best suits their circumstances. In bilateral descent, which is common in societies like the United States, kinship is traced through both the mother's and father's lines without preference, reflecting a more inclusive approach to family lineage.
A key difference between bilateral and unilateral descent (like patrilineal or matrilineal descent) is that the former acknowledges both parental lineages in determining relations and inheritance, while the latter focuses on just one. Kinship charts, utilizing a point of reference or 'EGO,' visually represent these relationships and help depict the complex web of familial ties under different descent systems.