Chatting with Eamon: Precursor Eggs

So, I was talking with my friend Eamon, when I, as always, bring up the topic of The Chicken or the Egg: which came first?
 Eamon thinks that the chicken came first, claiming that a regular bird, evolving over it's lifespan could become the chicken we know and love (to eat) today.
 I disagree: I feel that two different species, with traits similar to that of chickens, bred, and produced the chicken (which formed inside the egg: (hence my theory)), the parent species died out, leaving the chicken to breed with other birds, increasing the size of its race, and forming and evolving over the years.
 Eamon disagreed, he said that the chicken WAS a normal bird that developed the traits of a chicken (Fat) and was classified as such.
 I disagreed again: If someone becomes fat in their own lifespan, so long as it isn't genetics, (the only way this would be relevant) then it was it's own doing, and therefore couldn't be passed on to any further generation, making it a fat bird, and not a chicken.
 We then agreed to disagree, and talked about "Epic rap battles of history"
What is your theory? Leave your opinions below!