An egg is a single cell. Do you deny that you came from the combination of two single cells?
There is not a single cell in your body that performs anything but mitosis for replication. Not a single cell mates with another cell to create a new life, yet here we are.
It wasn't until single cells joined up and formed multi-cellular organisms that acted to protect the individual cells that sexual replication was formed as a method of sharing genetic information. Multi-cellular organism bacame much more organized and complex as time passed until they formed the great things we have today. It didn't require a creator, it wasn't a grand design, it happened.