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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 an egg according to some people, as egg-laying species pre-date the existence of chickens. To others, the chicken came first, seeing as chickens are merely domesticated Red Junglefowls. 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 Colebrook equation.
Ancient references to the dilemma are found in the writings of classical philosophers. Their writings indicate that the proposed problem was perplexing to them and was commonly discussed by others of their time as well.
Aristotle (384–322 BC) was puzzled by the idea that there could be a first bird or egg and concluded that both the bird and egg must have always existed:
If there has been a first man he must have been born without father or mother – which is repugnant to nature. For there could not have been a first egg to give a beginning to birds, or there should have been a first bird which gave a beginning to eggs; for a bird comes from an egg. 
The same he held good for all species, believing, with Plato, that everything before it appeared on earth had first its being in spirit."
Plutarch (46–126) referred to a hen rather than simply a bird. Plutarch discussed a series of arguments based on questions posed in a symposium. Under the section entitled "Whether the hen or the egg came first", the discussion is introduced in such a way suggesting that the origin of the dilemma was even older:
...the problem about the egg and the hen, which of them came first, was dragged into our talk, a difficult problem which gives investigators much trouble. And Sulla my comrade said that with a small problem, as with a tool, we were rocking loose a great and heavy one, that of the creation of the world..."
Macrobius (early 5th century), a Roman philosopher, found the problem to be interesting:
You jest about what you suppose to be a triviality, in asking whether the hen came first from an egg or the egg from a hen, but the point should be regarded as one of importance, one worthy of discussion, and careful discussion at that."
In System of Nature by Baron D'Holbach (1770, translated into English in 1797), he asks "was the animal anterior to the egg, or did the egg precede the animal?" (part 1, chapter 6).
Stephen Hawking and Christopher Langan argue that the egg came before the chicken, though the real importance of the question has faded since Darwin's On the Origin of Species and the accompanying Theory of Evolution, under which the egg must have come first, assuming the question intended "egg" to mean an egg in general rather than an egg that hatches into a chicken. According to Popular Science, the egg came first as it evolved prior to birds.
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?" This science does give new insight into an efficient and fast method of crystallization. It will help in research to devise better synthetic bone and research into how to store/sequester CO2 as limestone."
A previous analysis which came to another conclusion. Professor John Brookfield and Professor David Papineau argue since there was a "first" chicken, it must have come from an egg which pre-dated that chicken. An even earlier analysis which also came to another conclusion was made by Roy A. Sorensen in his one-page-article in 1992. He argued that although it is indeterminate which animal was the first chicken, the question of whether the chicken or the chicken egg came first has a determinate answer. Since an animal does not evolve into another species during its lifetime, and since organisms can fail to breed true, it is biologically necessary that the chicken egg came first. Biologist PZ Myers points out a further flaw in the 'protein-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.
The theory of evolution states that species change over time via mutation and sexual reproduction. Since DNA (deoxyribonucleic acid) can be modified only before birth, it can be argued that a mutation must have taken place at conception or within an egg such that a creature similar to a chicken, but not a chicken, laid the first chicken eggs. These eggs then hatched into chickens that inbred to produce a living population. Hence, in this light, both the chicken and the structure of its egg evolved simultaneously from birds that, while not of the same exact species, gradually became more and more like present-day chickens over time.
However, no one mutation in one individual can be considered as constituting a new species. A speciation event involves the separation of one population from its parent population, so that interbreeding ceases; this is the process whereby domesticated animals are genetically separated from their wild forebears. The whole separated group can then be recognized as a new species.
The modern chicken was believed to have descended from another closely related species of birds, the red junglefowl, but recently discovered genetic evidence suggests that the modern domestic chicken is a hybrid descendant of both the red junglefowl and the grey junglefowl. Assuming the evidence bears out, a hybrid is a compelling scenario that the chicken egg, based on the second definition, came before the chicken.
This implies that the egg existed before the chicken, but that the chicken egg did not exist until an arbitrary threshold was crossed that differentiates a modern chicken from its ancestors. Even if such a threshold could be defined, an observer would be unlikely to identify that the threshold had been crossed until the first chicken had been hatched and hence the first chicken egg could not be identified as such.
A simple view is that at whatever point the threshold was crossed and the first chicken was hatched, it had to hatch from an egg. The type of bird that laid that egg, by definition, was on the other side of the threshold and therefore not a chicken—it may be viewed as a proto-chicken or ancestral chicken of some sort, from which a genetic variation or mutation occurred that resulted in the egg being laid containing the embryo of the first chicken. In this light, the argument is settled and the egg had to have come first.
Judeo-Christian writings indicate God's creation of birds along with the rest of the universe. The Judeo-Christian story of creation describes God creating birds, and commanding them to multiply, but makes no direct mention of eggs. According to Genesis 1:
19 20 And God said, Let the waters bring forth abundantly the moving creature that hath life, and fowl that may fly above the earth in the open firmament of heaven. 21 And God created great whales, and every living creature that moveth, which the waters brought forth abundantly, after their kind, and every winged fowl after his kind: and God saw that it was good. 22 And God blessed them, saying, Be fruitful, and multiply, and fill the waters in the seas, and let fowl multiply in the earth.
A literal historic account of Genesis would place the chicken before the egg.
In Hindu writings, creation of birds (and other life forms) by God through superhuman beings is stated in Purāṇas and Dharmaśāstras. However, if one broadens one's definition of "an egg" to include non-chicken egg, the Hindu mythology also mentions a "cosmic egg" from which the universe as known to humans originated. In this sense this supreme egg comes before all creatures, including chickens and chicken eggs. This egg is known as Brahmanda ("Brahma, creator" and "anda", egg). The primordial egg is also depicted as a Lingam.
A world egg or cosmic egg is a creation myth of many cultures and civilizations linking the egg to birth. It embodies the idea of a silent universe, all at one bursting into activity and chaos. The yolk in some stories forms the ground and its white the sky (or vice versa). The first written record of the cosmic egg occurs on Egyptian papyrus and is likely connected with Thoth, God of the moon, who hatches the egg himself or emerges himself from the egg.
In Buddhism, Hinduism, as well as other Dharmic religions, there is the belief of the wheel of time which regards time as cyclical and with repeating ages, as some other cultures such as Mesoamerican (Aztecs, Mayan) and some native American Indians believe. Their idea of time gives a different answer to the question of "who is first." The concept of eternal return, which is well known in the Western culture through the writings of Nietzsche indicates that there is repetition of time. The assumption is that time is eternally repetitive, and therefore, there is no "first" in eternity; there is no creation. The answer then becomes: neither the egg nor the chicken is first. There is no "first" in a cyclical view of time. For further information:
The term "chicken-and-egg problem" is further commonly used to describe a situation that is not a philosophical dilemma, but one in which it is impossible to reach a certain desired outcome because a necessary precondition is not satisfied, while to meet that precondition in turn requires that the desired outcome has already been realized. For example, it has been argued that the transformation to alternative fuels for vehicles faces a chicken-and-egg problem: "it is not economical for individuals to purchase alternative fuels absent sufficient refueling stations, and it is not economical for fuel dealers to open stations absent sufficient alternative fuel vehicles". This is closely related to the economic concept of vicious circle, but in this kind of situation one that becomes a virtuous circle upon reaching a tipping point.