This isn't exactly brilliant, and I've posted this at various times and places for quite a few years, but (unusual for me) it is pretty brief. At conception, that single cell is:
* Genetically human, not anything else;
* Genetically unique, not genetically part of the mother;
* Alive;
* At the start of a growth and maturation process in a "programmed" pattern that, if not interrupted, extends from that single cell into geriatric adulthood.