Actually, "the" comes before them both in the question. Anyway, I've read enough novels to know the true answer. It is very obvious, that a lizard found himself a piece of sacred jade, where he cultivated until he evolved to a dragon, and unlocked it's MC cheats. Thus the Dragon MC used its dragon sexiness to gather a harem, but being of the greedy type, he deprived the eggs of dou qi, so only chickens hatched.
Anyone of you read tate no yuusha? There's a chapter that say Rat (The mad scienties) hates dragon because dragon is a horny beast that defiled many creatures that lead to many new species such as wyvern, drake, dragonewt and chicken! So Chicken is a descendant of a dragon and a bird.
Chickens did. Their ancestors evolved to reproduce by laying eggs. Birds are distantly related to dinosaurs, which are primitive reptiles that mostly laid eggs too.
This is what I was going to ask. If it's "a chicken's egg (as in, laid)" then the chicken must come first by definition, since he chicken must exist to create the egg. If it's "chicken egg (as in, pre-baby stage of a chicken)" then by definition the egg came first since the chicken can't exist without its egg stage of development. Then there's the "parents of an egg have different dna to its child that has dna considered to be that of a chicken" that makes sure it's not a closed loop. It's kinda English Language mixed with biology? Unless a chicken appeared without egg stage maybe, e.g. Supervirus altered an animal's dna that turned it into a chicken, etc.
In terms of evolutionary history, reproductive changes are the most delicate and slow changing, so it unlikely that one day that eggs rapidly developed as a way of shielding young, There are plenty of examples of egg laying creatures before the chicken and similar birds, so: egg was first Most importantly, the bird biology is pretty unique in terms of taking advantage of egg laying to change its internal morphology/structure/anatomy so radically compared to other living creatures. If feel like for this specific reason the egg would have had to been around first for birds to optimize to the advantages they enjoy.
chicken ; random chicken ancestor dino -> random chicken ancestor dino egg (slightly mutated) -> random chicken ancestor dino (slightly mutated) -> random chicken ancestor dino egg (mutated) -> random chicken ancestor dino who looks more like chicken -> random chicken ancestor dino who looks more like chicken egg (slightly mutated) -> random chicken ancestor dino who looks more like chicken egg (mutated) -> chicken -> chicken (egg) ... but I guess if you look at it sideway, it could be egg first... but at that time we still don't know whether the egg is a [normal -whatever creature it is] egg or [the animal we called chicken] egg hummm