You're asking a question that we've asked ourselves for a millennia

https://en.wikipedia.org/wiki/Ship_of_Theseus

Technically, we are not the same people that we were when we were born. The cells in our body have one by one been replaced with new ones and the old ones have died off. The things that make up my body are 100% different than when I was born, so I literally am not the same person, physically.

Maybe this is an indicator that there is more to what makes us, us, than just the physical assembly of atoms in our bodies. There are things I don't know that we'll ever get a full understanding of.