In most cases, an egg is a chicken. The chicken is an egg. It's like asking which came first: heads or tails. If you slice a coin in half to remove the obverse side, you don't get a one-sided coin. Which came first: inside or outside. If you remove all eggs, there are no chickens. If you remove all chickens, there are no eggs.
This is also the reason the sins of the father are visited upon the son. The son is* the father, he is suffering from his own sins.
*(50% at least.)