The chicken or the egg causality

dilemma A dilemma () is a problem offering two possibilities, neither of which is unambiguously acceptable or preferable. The possibilities are termed the ''horns'' of the dilemma, a clichéd usage, but distinguishing the dilemma from other kinds of p ...

is commonly stated as the question, "which came first: the

chicken The chicken (''Gallus gallus domesticus'') is a domesticated subspecies of the red junglefowl (''Gallus gallus''), originally native to Southeast Asia. It was first domesticated around 8,000 years ago and is now one of the most common and w ...

or the

egg An egg is an organic vessel grown by an animal to carry a possibly fertilized egg cell (a zygote) and to incubate from it an embryo within the egg until the embryo has become an animal fetus that can survive on its own, at which point the ...

?" 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'', to express a scenario of

infinite regress Infinite regress is a philosophical concept to describe a series of entities. Each entity in the series depends on its predecessor, following a recursive principle. For example, the epistemic regress is a series of beliefs in which the justi ...

, or to express the difficulty of sequencing actions where each seems to depend on others being done first.

Plutarch Plutarch (; , ''Ploútarchos'', ; – 120s) was a Greek Middle Platonist philosopher, historian, biographer, essayist, and priest at the Temple of Apollo (Delphi), Temple of Apollo in Delphi. He is known primarily for his ''Parallel Lives'', ...

posed the question as a philosophical matter in his essay " The Symposiacs", written in the 1st century CE.

Ancient legacy

The question represents an ancient folk paradox addressing the problem of origins and

first cause The unmoved mover () or prime mover () is a concept advanced by Aristotle as a primary Causality (physics), cause (or first uncaused cause) or "Motion (physics), mover" of all the motion in the universe. As is implicit in the name, the moves oth ...

Aristotle Aristotle (; 384–322 BC) was an Ancient Greek philosophy, Ancient Greek philosopher and polymath. His writings cover a broad range of subjects spanning the natural sciences, philosophy, linguistics, economics, politics, psychology, a ...

, writing in the fourth century BCE, 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 Macrobius Ambrosius Theodosius, usually referred to as Macrobius (fl. AD 400), was a Roman provincial who lived during the early fifth century, during late antiquity, the period of time corresponding to the Later Roman Empire, and when Latin was ...

wrote that while the question seemed trivial, it "should be regarded as one of importance". By the end of the 16th century, the well-known question seemed to have been regarded as settled in the Christian world, based on the origin story of the

Bible The Bible is a collection of religious texts that are central to Christianity and Judaism, and esteemed in other Abrahamic religions such as Islam. The Bible is an anthology (a compilation of texts of a variety of forms) originally writt ...

. In describing the creation of animals, it allows for a first chicken that did not come from an egg. However, later

Enlightenment Enlightenment or enlighten may refer to: Age of Enlightenment * Age of Enlightenment, period in Western intellectual history from the late 17th to late 18th century, centered in France but also encompassing (alphabetically by country or culture): ...

philosophers began to question this solution. Carlo Dati in the mid 17th-century published an erudite satire on the subject.

Scientific resolutions

Although the question is typically used metaphorically,

evolutionary biology Evolutionary biology is the subfield of biology that studies the evolutionary processes such as natural selection, common descent, and speciation that produced the diversity of life on Earth. In the 1930s, the discipline of evolutionary biolo ...

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 Anaximander ( ; ''Anaximandros''; ) was a Pre-Socratic philosophy, pre-Socratic Ancient Greek philosophy, Greek philosopher who lived in Miletus,"Anaximander" in ''Chambers's Encyclopædia''. London: George Newnes Ltd, George Newnes, 1961, Vol. ...

when addressing the paradox. If the question refers to eggs in general, the egg came first. The first

amniote Amniotes are tetrapod vertebrate animals belonging to the clade Amniota, a large group that comprises the vast majority of living terrestrial animal, terrestrial and semiaquatic vertebrates. Amniotes evolution, evolved from amphibious Stem tet ...

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 The red junglefowl (''Gallus gallus''), also known as the Indian red junglefowl (and formerly the bankiva or bankiva-fowl), is a species A species () is often defined as the largest group of organisms in which any two individuals of the a ...

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. The process by which the chicken arose through the interbreeding and domestication of multiple species of wild jungle fowl is poorly understood, and the point at which this evolving organism became a chicken is a somewhat arbitrary distinction. Whatever criteria one chooses, an animal nearly identical to the modern chicken (i.e., a proto-chicken) laid a fertilized egg that had DNA making it a modern chicken due to mutations in the mother's ovum, the father's sperm, or the fertilised

zygote A zygote (; , ) is a eukaryote, eukaryotic cell (biology), cell formed by a fertilization event between two gametes. The zygote's genome is a combination of the DNA in each gamete, and contains all of the genetic information of a new individ ...

. It has been suggested that the actions of a

protein Proteins are large biomolecules and macromolecules that comprise one or more long chains of amino acid residue (biochemistry), residues. Proteins perform a vast array of functions within organisms, including Enzyme catalysis, catalysing metab ...

found in modern chicken eggs may make the answer different. In the uterus, chickens produce ovocleidin-17 (OC-17), which causes the formation of the thickened

calcium carbonate Calcium carbonate is a chemical compound with the chemical formula . It is a common substance found in Rock (geology), rocks as the minerals calcite and aragonite, most notably in chalk and limestone, eggshells, gastropod shells, shellfish skel ...

shell around their eggs. Because OC-17 is expressed by the hen and not the egg, the bird in which the protein first arose, though having hatched from a non-reinforced egg, would then have laid the first egg having such a reinforced shell: the chicken would have preceded this first 'modern' chicken egg. However, the presence of OC-17 or a homolog in other species, such as turkeys and finches suggests that such eggshell-reinforcing proteins are common to all birds, and thus long predate the first chickens.

Disputations

On 24 July 2024, two men began a chicken-or-egg debate at a party with alcohol in Indonesia. One man became so emotionally enraged he left and returned with a knife, stabbing the other 15 times and killing him. It is uncertain what side of the argument — chicken or egg — the killer took.

Ancient legacy

Scientific resolutions

Disputations

See also

References

Further reading