Well, it all depends on how you look at it.
If you are a creationist, then chickens would have come first, as God created adult creatures.
If you are an evolutionist (which is a silly idea), then the egg would most certainly have come first. Genetics makes everything what it is as it is born. The genetics of the pre-rooster and pre-chicken would be of one species, but then their genetic data would have mutated enough to create a chicken, which woudl have to be in an egg as it is still developing. Egg.
As always- None of my statements are evaluated by the FDA.
My advice is not intended to diagnose, treat, cure or prevent any diseases unless prescribed by a health practitioner. All information is provided for educational purposes only and should not replace the advice of your medical doctor.
(but your medical doctor will probably end up killing you