I know for a fact the chicken came first. whatever it began as we're calling a chicken. Because we hadn't named it then. Just as we start off as sperm. This chicken(sperm) evolved and evolved.. had a child who had a child which then eventually gave birth to an egg from which the child hatched.

Trust me, I'm an eggspert, it's OK, it's Friday you can be eggcited.

This explains my theory.