In genealogy

Genealogy

Genealogy is the study of families and the tracing of their lineages and history. Genealogists use oral traditions, historical records, genetic analysis, and other records to obtain information about a family and to demonstrate kinship and pedigrees of its members...

 or in phylogenetic studies of evolutionary biology an antecedent, antecessor or antecedents are predecessors in a family line. I am the descendants of my grandparents, they are my antecedents. This term has particular utility in evolutionary coalescent theory

Coalescent theory

In genetics, coalescent theory is a retrospective model of population genetics. It attempts to trace all alleles of a gene shared by all members of a population to a single ancestral copy, known as the most recent common ancestor...

, which models the process of genetic drift in reverse time.

Antonym: descendant

Lineal descendant

A lineal descendant, in legal usage, refers to a blood relative in the direct line of descent. The children, grandchildren, great-grandchildren, etc...