Some chose the names of their most ancient known ancestor.

These are the known ancestors of Afonso Henriques, going back five generations.

Earliest reference date back to 1670, with Efrem son Petrov being the oldest of known ancestors.

Since they both had well documented pedigrees, they have hundreds of known ancestors in common before that time.

The first known ancestor was Andrew, who lived in the early 12th century.

The oldest known ancestor is Jakob van Heker who died in 1440.

His first known ancestor was a Thomas Colynborn, of Marleberg, who lived before 1377.

Or was it something more specific about particular known ancestors?

In 1994, White discovered what was then the oldest known human ancestor: 4.4 million-year-old Ar.

The oldest known ancestor of the dromedary is the Protylopus.