The egg obviously came first. There's no doubt about it. Birds and animals laying eggs has been a trait that has been around for a very long time. Then the question is what came first. let's forget about the egg for a sec. Before the chicken, there was pre-chicken, A bird so close to being chicken, the next generation was bound to be the species that we today call chicken. The Chronologially: The Pre-chicken lays the egg. Egg exists. Chicken hatches from the egg. Pre-chicken->Egg->Chicken. And since the question is, Egg or chicken. The egg obviously came before the chicken.