A proto-chicken laid an egg which became the progenitor of the modern-day chicken, but this question is more of semantics since the proto-chickens themselves hatched from eggs incubated by their parents, in Aristotelean metaphysics, actuality precedes potentiality, for the potential to become actual, a causative agent that is in the state actuality must act upon it, so the actual chicken (proto-chicken) must precede the potential chicken (egg of modern-day chicken). Therefore, one should not misconstrue that eggs can precede the egg-laying species themselves because that is erroneous.