"Which came first, the chicken or the chicken-egg?" Evolutionarily speaking, the chicken and the chicken-egg came at the same time. "Huh?", you say, but it's true. Let me explain: individual organisms don't evolve, populations of organisms do. Let me explain further:
Once upon a time, non-chickens roamed free. Human hunted the non-chickens for they were tasty. To lazy to have to hunt, humans captured some of the non-chickens alive and started breeding them. The wild non-chickens and the captured ones both continued to live and breed, without intermingling. One day, the captured non-chickens were noticibly different from their wild cousins, they were now chickens. But in no specific point in the evolutionary history did a non-chicken lay an egg that hatched a chicken.
Just like on a light spectrum, where you can easily point to green ("non-chicken") or yellow ("chicken") but you can't point to the exact spot where one end and the other begin, because that's subjective. It's the same with species. So, necessarily, due to the indefinite nature of species, the chicken and the chicken-egg evolved simultaneously.
Next time on Important Philosphical Questions Answered by Science: how many angels can dance on the head of a pin?