What does that have to do with Christianity?
But to answer your question about the age old riddle: Eggs are much older than chickens. Dinosaurs laid eggs, the fish that first crawled out of the sea laid eggs, and the weird articulated monsters that swam in the warm shallow seas of the Cambrian Period 500 million years ago also laid eggs. There are thousands of pieces of fossilized evidence to support this.
We all evolved from that mess and even our own birth is the result of a sperm and an egg that looks exactly the same under a microscope, with the only exception of your Jesus.