Chicken or the egg

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A chick hatching from an egg

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.[1]

Scientific resolution[edit]

If the question refers to eggs in general, the egg came first, as the first egg-laying animals evolved millions of years prior to birds.[2]

If the question refers to chicken eggs specifically, the answer is again 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).[3][4] 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."[5]

Philosophical perspective[edit]

Ancient philosophers were not aware of biological evolution. 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.[6]

See also[edit]


  1. ^
  2. ^ Engber, Daniel (2013). "FYI: Which Came First, The Chicken Or The Egg?". Popular Science. Bonnier Corporation. 282 (3): 78. Retrieved 15 February 2013. 
  3. ^ "Finally answered! Which came first, the chicken or the egg?". MNN - Mother Nature Network. 
  4. ^ "Which Came First, the Chicken or the Egg?". Time. Retrieved 29 January 2017. 
  5. ^
  6. ^ François Fénelon: Abrégé des vies des anciens philosophes, Paris 1726, p. 314 (French). Translation: Lives of the ancient philosophers, London 1825, p. 202 (English)