There was more than one to start with so it wasn't a problem.
So, which came first the eggs or the chicken?
egg
YES they reproduce sexually just like humans do
The answer is neither because an egg has to be incubated and a chicken needs a mate to reproduce the true answer is two chickens a hen and a chicken.
They lay eggs to reproduce, even if there is no male.
The true answer is very simple, in fact, it is so simple people do not want to believe it. God created the chicken in the beginning with the capacity to reproduce, the egg can not reproduce on it's own.
The first chicken killer
You can not "own" a chicken in minecraft. If you hold wheat in your hand the chicken will follow you but it will never belong to you. You could always build a pen to lock chickens in. From there you can help them reproduce by feeding them wheat.
Technically the ancestors of the chicken came first.
chicken.
The chicken
The chicken
domesticated chicken