It is a complex unilineal descent group where a person traces ancestry from both mother and father for different things at different times. However, at a single point, the descent is traced from a single parent only.

Features: 

1. The origin of double descent is believed to be a transition with a matrilineal descent to a patrilocal residence. It helps to prevent the problems of simple unilineal groups like segmentation and diminishing groups.
2. Matri and patri groups are simultaneously operative
3. This system works on the distribution of rights between 2 unilineal groups
4. Conflict between the two unilineal descent groups is avoided by conferring equal rights to both sexes
5. Demographic vagaries of unilineal descent are avoided in double descent

Case study: 

Ashanti of Ghana demarcates materialistic(land, cattle, ornaments) and non-materialistic things( social status, prestige, etc). Materialist things are inherited from the mother and non-materialistic things are inherited from the father. Ashanti believe that the soul is given by the father and the body is given by the mother.

Conclusion: 

In recent times, due to the impact of western culture, such descent systems are disappearing and giving way to bilateral systems of the modern age.