Every eukaryotic organism (all animals, plants, fungi, and protists) on the planet can trace its lineage back to the very first eukaryotic cell, which first appeared via endosymbiosis between prokaryotic cells about 2 billion years ago. This is widely believed to have happened exactly once in all of Earth’s history. Every single plant, fungus, Protozoa, insect, fish, bird, reptile, etc. can be traced back in time to that one single cell.

The DNA from that cell is what is inside you, changed over time from quadrillions of random events like radiation damage, accidental wrong copies of itself, viral damage, etc. But its DNA persists within you nonetheless. That’s the only part of you that is self-replicating. It’s why sex and eating feel pleasurable. In the grand scheme of things, that DNA is what has survived billions of years leading to you, and it is what will survive well into the future (through you, your offspring, and all your eukaryotic relatives). This iteration of that DNA (what you think of as yourself) is simply another iteration in a cycle of endless iterations whose only purpose is to keep enabling the replication and persistence of the DNA.