Hmm, this is interesting, but I'm going with the egg... just my beliefs on evolution, though we cant prove it:
Primordial Soup + Catalyst -> Bateria & Amobeia (sp?) (Reproduce with mitosis) -> Larger Organisms (mitosis again) -> Sea Creatures (live birth?) -> Bigger Sea Creatures -> Amphibians -> Bunch of other stuff -> Chicken
The important part is the Larger Organisms forming the small sea creatures (trioblites etc), they must've formed through mitosis, I think, sort of like the way that a child is created through the egg spliting again and again until some fancy stuff happens then more cells appear...
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All just my theory of course
P.S. The chicken was born from a mutated egg