Quote Originally Posted by MrShrike View Post
No I don't accept this is correct. I understand your point about speciation, but we're not talking about species, we're talking about individuals. Basically, what we're doing is looking at each individual creature in the evolution of the modern chicken and saying "does THIS individual meet the definition of chicken". Then we're finding the first individual that met this definition. Unless we include "is fertile" in that definition (which I don't think we should, given that a modern chicken that is infertile is still a chicken), the fertility of our first chicken candidate, and whether or not it contributed it's own offspring to the general evolution of the species from not-chicken to chicken is actually irrelevant. There is similarly also no requirement that any offspring it did have needed to be chickens either. Taking into account how evolution of a species actually works, it's just as likely that any offspring our first chicken may had have were not-chickens as well.
My explanation WAS talking about individuals; I am saying that if you look at all the individual organisms in the evolutionary history of the modern chicken, you are never going to find a situation where there's a creature that definitively isn't a member of the modern species, laying an egg that hatches into a creature that definitively is a member of the modern species. I had assumed that the definition of "chicken" was "a member of the species G. gallus. If that's not your definition of chicken, then what is?