[jonny_eh]

It's not even that simple. Evolution occurs gradually, so gradually in fact that there is no "first" chicken. Any given chicken/ancestor you pick will be so genetically close to its parents/children, that they're the same species by any definition.

Another way of putting the paradox is "Which chicken arrived first, the chicken or its parent"?

[vletal]

Chicken. If we establish some trait of a chicken we could be able to trace the first bird wich had the specific gene combination and it's parents had not. Still a well defined non paradox.