Memes

You're right in that it's not meant to have an answer as it's normally told philosophically. But the biological and evolutionary answer is that there is no dividing line to give that answer because species don't change with individuals but with large populations over great amounts of time. We see those lines because we find fossils of things related to but different enough to others to call them a different name. And the real mind blower is that almost all creatures that did exist never left fossils to find.

The false dilemma of the chicken and the egg shares the same misunderstanding that the "missing link" fallacy does. There's no line between things except over time and thousands of generations.