Bhagavad Gita, Chapter 10, Verse 6

The seven great Rishis as well as the four ancient Manus, possessed of powers like Me due to their thoughts being fixed on Me, were born of My mind; from them are these creatures in the world.

The lineage traced here runs all the way back through sages and Manus to one real starting point.

Naming this ancestry isn't decorative, it grounds every living person's line in something specific rather than vague or mythic. Real descent is described here, not a loose metaphor.