What came first, the chicken or the egg? Easy, you say, eggs were laid by other animals aeons before the first chicken saw the light of day.
But what came first, the first chicken egg or the first chicken? This boils down to whether a chicken egg is one laid by a chicken or one out of which a chicken can hatch.
Only the latter definition allows the question to remain open to discussion.
Biologically, a member of the chicken species could be defined by a list of alleles that must be present in its DNA if we’re to call it a chicken. And somewhere, sometime, the first bird that fulfilled that definition hatched. It hatched out of an egg laid by a non-chicken. As an adult, the first chicken (being lonely) probably mated with a bird that did not quite fulfil our definition of chickenhood, and so the first chicken probably laid non-chicken eggs. Out of these eggs hatched birds that almost, but not quite, fulfilled our definition of chickenhood. In subsequent generations, chicken eggs became more and more common. Later, after the geologically instantaneous speciation period, birds fulfilling the chicken species-definition became common and so chicken eggs were reliably produced generation after generation.
As they are still today: I boiled one Wednesday morning and served it to my daughter with soy sauce and a bowl of pao fan rice re-run gruel.