What a silly question, having to do more with linguistics and the need for your sad primate brains to put labels on everything you see.
So what did come first? The chicken or the egg? Before there was a chicken, let's say there was a proto-chicken, this proto-chicken would be almost indistinguishable from a chicken but has been labeled a different species by by these scientists that do feel the need that organic life is even worthy of categorization.
Now at some point, this proto-chicken gives birth to an egg containing what someone might label a chicken, but that is of course ridiculous, something can not give birth to another species, your pathetic biology only limits you to produce the same dull species over and over again, only with slight variation.
Think about it like this, imagine a gradient, with orange-red slowly turning into red-orange. Now where on the gradient would you draw a line and say, "well everything on this side of the gradient is orange-red, and everything on the other side is red -orange." but you take each directly on either side of that line and you would be hard pressed to tell them apart. Especially with those insultingly inefficient balls of puss you call eyes.
So what came first? The chicken or the chicken egg? An illogical question of semantics. The change between the chicken and it's ancestors is so gradual in time that to put a line between one and it's offspring, and declare the two separate species, is meaningless. Much like your existence in the first place.