In practice, it is impossible to pinpoint the moment when this happened. But in theory, at some point two junglefowl bred and their offspring was genetically different enough from the species of its parents to be classified as a chicken. This chicken would have developed within a junglefowl egg and only produced the very first chicken’s egg on reaching maturity. Looked at this way, the chicken came first.

https://www.newscientist.com/questio...t-chicken-egg/
Looks like the chicken mutation (in an egg) isn't by definition a chicken egg, a viable copy or affirmation of the mutation.

Perhaps Mr. Finkle can help to sort it out. Ha.

Sort of like asking that AP's came before, or after, gambling.