What term refers to the kind of descent in which people choose the descent group that they join?

The term that refers to the kind of descent in which individuals choose the descent group they join is "ambilineal descent." In this system, individuals have the flexibility to affiliate with either their mother's or father's lineage, allowing for a more fluid and adaptive approach to kinship and inheritance. This contrasts with unilineal descent systems, where membership is strictly determined by one's maternal or paternal line.