Final answer:
The difference between unilineal and bilateral kinship systems lies in the method of tracing lineage; unilineal follows a single gendered line, whereas bilateral traces both maternal and paternal lines.
Step-by-step explanation:
The main difference between unilineal and bilateral kinship systems is how descent and lineage are traced. Unilineal descent, which is subdivided into patrilineal, matrilineal, and ambilineal, traces an individual's lineage through either the father's or the mother's side exclusively. For example, in a patrilineal society, lineage is traced through the father's line, and often the family surname is passed down from father to son. Conversely, bilateral kinship, also known as lineal or bilineal, traces an individual's lineage through both the mother's and the father's sides, reflecting a more inclusive family unit where maternal and paternal relatives contribute to one's ancestry.
Bilateral descent is common in societies like the United States, where both paternal and maternal ancestors are considered equally part of one's family tree. This system results in minimal distinctions between family members outside the immediate nuclear family regarding kinship rights and responsibilities.