That has been long since solved with evolutionary genetics.
The egg.
What produced it just happened not to be a chicken. Something close, but not
quite.
Ah, so then you agree that it wasn't a chicken egg? ie Chicken came first
(from non-chicken egg), then laid chicken egg.
> No, no, you've got it backwards.
> A non-chicken laid a chicken egg (i.e. the egg's genes were those of a
chicken), from which hatched a chicken.