This is the rational, informed answer. I, unencumbered by any knowledge of biology, just tried to make up a cute story.
I’m a bio/phil double major!!! I would say that there wasn’t a distinct, first member of the chicken species, for the chickens have ancestors just like homo sapiens do, and there’s some fluidity there. *loud, booming voice* evolution *crowd goes insane*
…but I don’t like this answer because I want nothing to do with an explanation that denies the existence of an OG Chicken.
The chicken, of course. There’s no way a chicken could’ve hatched from an egg laid by a non-chicken, right? The first chicken could not have been born from an egg, just as Adam and Eve weren’t birthed by humans. Where did it come from, then? The only plausible explanation is that this chicken was causa sui - the self-caused chicken. The First Chicken (capitalized to show proper respect for this wondrous being (we could also call it the O.G. Chicken)) came into being by means of its own will - such was its godlike power. Then it laid a thousand eggs and populated the world with its chicken progeny.