The egg came before the chicken.
If you think about it, genetic material remains the same during the chicken’s life, but mutations occur during reproduction, and are passed down to the offspring (egg). Creationistly speaking, if a crocodile gave birth to a duck, (thus proving evolution lol), the egg wouldn’t be a crocodile egg, but a duck egg.
The second argument is that, eggs existed long before chickens. Eggsperts have reason to believe that amniotic eggs evolved 320 million years ago. Therefore, the egg came before the chicken.
You can follow this link to my archaeoptryx post.