The chicken or the egg causality dilemma is commonly stated as "which came first, the chicken or the egg?" To ancient philosophers, the question about the first chicken or egg also evoked the questions of how life and the universe in general began.
Cultural references to the chicken and egg intend to point out the futility of identifying the first case of a circular cause and consequence. It could be considered that in this approach lies the most fundamental nature of the question. A literal answer is somewhat obvious, as egg-laying species pre-date the existence of chickens. However, the metaphorical view sets a metaphysical ground to the dilemma. To better understand its metaphorical meaning, the question could be reformulated as: "Which came first, X that can't come without Y, or Y that can't come without X?"
An equivalent situation arises in engineering and science known as circular reference, in which a parameter is required to calculate that parameter itself. Examples are Van der Waals equation and the famous Colebrook equation.
Responses to the dilemma
Professor Mark Rodger and Dr David Quigley, from the University of Warwick, who helped develop a recent study with colleagues from Sheffield University, point out that in fact a key chicken protein, ovocleidin-17, which helps in the formation of the egg's hard shell, actually comes both before and after the egg shell. They say that this chemical quirk actually makes the question of which came first even more pointless than before. As Professor Mark Rodger says "Does this really prove the chicken came before the egg? Well this actually further underlines that it's a fun but pointless question. This science does however give new insight into an efficient and fast method of crystallisation. It will help in research to devise better synthetic bone and research into how to store/sequester CO2 as limestone."
However, this may contradict a previous analysis which came to another conclusion. Professor John Brookfield and Professor David Papineau argue since there was "first" chicken, it must have come from an egg which pre-dated that chicken. Biologist PZ Myers points out a further flaw in this argument, in that other birds make use of different kinds of proteins for producing eggs, and that the evolution of ovocleidin was not coincident with the evolution of eggs; ovocleidin developed from prior proteins, which were used to form eggs since before birds branched away evolutionarily from reptiles.
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