It isn't clear that there was a specific entity that could be widely considered alive that suddenly appeared one day at all.

There could have been millions of years of complex processes going on which was sort of a gradient from "definitely not alive" to "definitely alive".

Microbes can accept genetic information much more readily than animals do with unrelated forms, and all sorts of genes have probably disappeared in the last billion years. How would one define not ancestral to modern life vs ancestral.

Even if all the genes of some creature are no longer extant, they could arguably have shaped the evolution of genes that still are,so there is still some remaining influence.