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The chicken or the egg causality dilemma is commonly stated as "which came first: the chicken or the egg?". The dilemma stems from the observation that all chickens hatch from eggs and all chicken eggs are laid by chickens. "Chicken-and-egg" is a metaphoric adjective describing situations where it is not clear which of two events should be considered the cause and which should be considered the effect, or to express a scenario of infinite regress. Plutarch posed the question as a philosophical matter in his essay "The Symposiacs", written in the 1st century CE.

Ancient paradox

The question represents an ancient folk paradox addressing the problem of origins and first cause. It sets up two seemingly-compelling principles, that all chickens hatch from eggs and all (chicken) eggs come from chickens, in a manner that means no starting point is possible. Aristotle, writing in the fourth century B.C., would describe the problem, "There could not have been a first egg to give a beginning to birds, or there would have been a first bird which gave a beginning to eggs; for a bird comes from an egg." He concluded that this was an infinite sequence, with no true origin. Plutarch, writing four centuries later, specifically highlighted this question as bearing on a "great and weighty problem (whether the world had a beginning)." In the fifth century CE, Macrobius wrote that while the question seemed trivial, it "should be regarded as one of importance."

By 1600, the well-known question seemed to have been regarded as settled in the Christian world, based on the origin story of the Bible. In describing the creation of animals, it allows for a first chicken that did not come from an egg. However, later enlightenment philosophers began to question this solution.

Scientific resolution

Although the question is typically used metaphorically, biology provides literal answers, made possible by the Darwinian principle that species evolve over time, and thus that chickens had ancestors that were not chickens, similar to a view expressed by the Greek philosopher Anaximander.

If the question refers to eggs in general, the egg came first. The first amniote egg — that is, a hard-shelled egg that could be laid on land, rather than remaining in water like the eggs of fish or amphibians — appeared around 312 million years ago. In contrast, chickens are domesticated descendants of red junglefowl and probably arose little more than eight thousand years ago, at most.

If the question refers to chicken eggs specifically, the answer is still the egg, but the explanation is more complicated. An animal nearly identical to the modern chicken (i.e., a proto-chicken) laid a fertilized egg that had DNA identical to the modern chicken (due to mutations in the mother's ovum, the father's sperm, or the fertilised zygote). Put more simply by Neil deGrasse Tyson: "Which came first: the chicken or the egg? The egg — laid by a bird that was not a chicken."

See also

• Catch-22 (logic)

References

1. Plutarch of Chaeronea. The Symposiacs Question III. https://ebooks.adelaide.edu.au/p/plutarch/symposiacs/complete.html#section15.
2. O'Brien, Carl Séan (2015). The Demiurge in Ancient Thought. Cambridge, England: Cambridge University Press. p. 106. ISBN 978-1-107-07536-8.
3. ^ Sorensen, Roy (2003). A Brief History of the Paradox: Philosophy and the Labyrinths of the Mind. Oxford: Oxford University Press. pp. 4–11.
4. ^ Fabry, Merrill (2016-09-21). "Now You Know: Which Came First, the Chicken or the Egg?". Time Magazine. Retrieved 2017-07-11.
5. Benton, Michael J.; Donoghue, Philip C. J. (2007-01-01). "Paleontological Evidence to Date the Tree of Life". Molecular Biology and Evolution. 24 (1): 26–53. doi:10.1093/molbev/msl150. ISSN 0737-4038.
6. Miao, Y-W; Peng, M-S; Wu, G-S; Ouyang, Y-N; Yang, Z-Y; Yu, N; Liang, J-P; Pianchou, G; Beja-Pereira, A (2012-12-05). "Chicken domestication: an updated perspective based on mitochondrial genomes". Heredity. 110 (3): 277–282. doi:10.1038/hdy.2012.83. ISSN 1365-2540.
7. Sorensen, Roy A. (1992). "The Egg came before the chicken". Mind. 101 (403): 541–542.
8. Breyer, Melissa (2013-02-11). "Finally answered! Which came first, the chicken or the egg?". Mother Nature Network. Retrieved 2017-07-11.
9. Neil deGrasse Tyson (2013-01-28). "Just to settle it once and for all: Which came first the Chicken or the Egg? The Egg -- laid by a bird that was not a Chicken". Twitter. Retrieved 2017-07-11.

• Paradoxes
• Chickens
• Eggs in culture
• Metaphors referring to birds