Has there been any serious scientific inquiries into answering this age old question?
closed as not constructive by Mad Scientist Apr 5 '12 at 18:55
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Most theories about origin of life say that unicellular organisms were first and multicellularity (like chicken) evolved much later, so in that meaning egg (single cell)* was first. Also, almost all chicken ancestors lay eggs (primitive birds, non-avian reptiles, amphibians, fishes and so on...) so eggs existed much earlier than chickens.
*in the meaning of zygote. The development of chicken embryo starts in hen's oviducts, so it's not a single cell at the moment when hen lays it (Gilbert, 2000).
This is a classic case of "it depends on the context."
- The Egg: As Marta Cz-C points out, the amniotic eggs that chickens lay were inherited virtually unmodified from their theropod dinosaur ancestors. So when considering the type of eggs, the egg came first.
- The Chicken: From a systematic perspective, you must first have an animal that you would call a chicken before it can lay a "chicken" egg. So considering the animal, the chicken.
The question makes the false assumption that chicken and eggs are different life forms.
A life form at stage x is not a different life form than that very life form at stage y.
You might as well ask of which came first, a 7 year old kid or an 8 year old kid.
But they are the same thing and therefore this question is invalid.
Dunno about any serious scientific inquiries into the answer but I always thought the answer is egg. At some point the modern chicken has come into being as the progeny of two pre-modern chickens, however it had to be an egg before it could be a chicken and its parents couldn't have been modern chickens.
However, all that presupposes that you can draw a line in the evolutionary history of the modern (extant) chicken and say this is modern and what goes before is not. I dunno if that really can be done.
Edit: came across this guardian article: http://www.guardian.co.uk/science/2006/may/26/uknews
"Whether chicken eggs preceded chickens hinges on the nature of chicken eggs," said panel member and philosopher of science David Papineau at King's College London.
"I would argue it's a chicken egg if it has a chicken in it. If a kangaroo laid an egg from which an ostrich hatched, that would surely be an ostrich egg, not a kangaroo egg. By this reasoning, the first chicken did indeed come from a chicken egg, even though that egg didn't come from chickens."
And from Prof. Brookfield of the University of Nottingham:
The first chicken must have differed from its parents by some genetic change, perhaps a very subtle one, but one which caused this bird to be the first ever to fulfil our criteria for truly being a chicken; Thus the living organism inside the eggshell would have had the same DNA as the chicken that it would develop into, and thus would itself be a member of the species of chicken