Tuesday, March 10, 2009

Wednesday, December 20, 2006

Friday, November 24, 2006

Which Came First - Chicken or Egg?

The chicken or the egg is a reference to the causality dilemma which arises from the expression "which came first, the chicken or the egg?". Since both the chicken and the egg create the other in certain circumstances (a chicken emerges from an egg; an egg is laid by a chicken) it is ambiguous which originally gave rise to the other. Purely logical attempts to resolve the dilemma result in an infinite regress, since an egg was caused by a chicken, which was caused by an egg, etc. Since every chicken originates from its egg, it seems obvious the egg came first. Put simply, the reason is down to the fact that genetic material does not change during an animal's life. The solution may require an examination of syntax and may rely on verification from advances in modern genetic science. When used in reference to difficult problems of causality, the chicken and egg dilemma is often used to appeal to the futility of debate and lay it to rest.

History of the problem

The earliest reference to the dilemma is found in Plutarch's Moralia, in the books titled "Table Talk," in 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 as to suggest 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..."

Various answers have been formulated in response to the question, many of them humorous.

As suggested by the alternative definitions and solutions given below, the chicken-or-egg dilemma has multiple semantic variants and can thus be viewed as an exercise in semantics. Regarding at least two of these variants, the field of biology contains decisive contextual information. Although the problem has been around in one form or another for millennia, making it difficult or impossible to know who first "solved" it, the biological information needed to resolve all of the obvious semantic variants has only been available for decades.

A modern analysis covering all of the major variants was authored by Christopher Langan, published in 2001 on the Mega Foundation website[1], and subsequently included in his book of essays, The Art of Knowing [1]. It appeared again in The Improper Hamptonian [2], was included in abbreviated form in a 2001 Long Island Newsday Q&A column featuring Langan [3], and was compactly summarized in Langan's 2001 Popular Science interview.

A CNN article on May 26, 2006 featured an analysis, according to which the egg came first [2]. The key criteria on which CNN bases its answer, involving relatively recent findings from reproductive and evolutionary biology, are identical to several of those cited in the prior analysis.

Assuming a chicken egg

In this case, the egg is assumed to be a chicken's egg. This is an obvious assumption since the question itself implies a link between the two.

If one assumes the egg to be a chicken egg then one must define what a chicken egg is:

  • If: A chicken egg will hatch a chicken

Then a bypass is allowed: An animal that was not a chicken laid the chicken egg which contained the first chicken. In this case the egg came first.

  • If: A chicken egg is the egg that a chicken lays

Then a bypass is allowed: A chicken (that hatched from a non-chicken egg) laid an egg (a chicken egg). In this case the chicken came first.

  • If: A chicken egg will hatch a chicken and A chicken egg is the egg that a chicken lays

Then there may be an error of definition. If the definition of "chicken" used does not refer to "chicken eggs", then the chicken must come first, because without chickens there cannot be any chicken eggs.

Biological Answers

In this case, the egg is not assumed to be a chicken egg. In effect this changes the question to: "Which came first, a chicken or any egg".

From a cellular biology point of view this question can be answered quite easily. The egg came first because any female sex cell is called an egg.

If the egg is defined structurally as the hard shelled thing, and the chicken a feather covered animal, the answer is still simple. Evolutionary scientists believe the first hard shell egg was the amniotic egg laid around 300 million years ago, and was laid by the animal who was the link between amphibians and reptiles. One of the first dinosaurs that we know had feathers was the Archaeopteryx, and came much later. Modern birds would not arise until 150 million years ago, descending from theropod dinosaurs.

In this case, the first chicken must have been the mutated offspring of a proto-chicken that laid the egg containing the first true chicken. In any case, this creature hatched from a recognizable egg. After all, the question is purposefully ambiguous -- it is not, "Which came first, the chicken or the chicken egg?"

The crux of the matter is how to biologically define 'a chicken'. What level of genetic similarity or structural similarity determine whether an organism is a chicken? One can only define what was the first chicken after the fact, thus any definition of the first chicken becomes arbitrary. The question 'which came first?' ignores the complicated reality of speciation. The concept of species is an abstraction intended to categorize a broad swath of genomes and their subsequent phenomes. If one were to do away with approximate categories, each individual 'chicken' actually represents a unique genotype. Under this definition, if a 'chicken' possessing genome A were to lay an egg possessing genome B, then an egg of genome B is antecedent to an animal possessing genome B and that the parent--genome A--is antecedent to, yet different from the egg of genome B. Hence, in an absolute sense, the egg came before the 'chicken.'

According to the principles of speciation, neither the chicken nor the egg came first, because speciation does not occur in simple, obvious units. In fact, evolution is about a slow transition in an overall population. What qualifies as "chicken" (ignoring the many diverse modern types of chicken) involves a wide range of genetic traits (alleles) that are not encompassed in a single individual and continue to be modified from generation to generation.

The transition from non-chicken to chicken is a grey area in which several generations are involved, and therefore which includes many many chicken-and-egg events, with no one step representing the whole. Since the result of the process is an incomplete transition into various new characteristics rather than one single blueprint, a new species, "chicken", is only identified in hindsight when the species can be obviously identified as different from its ancestral stock.

Theological answers

According to creationists who believe in Biblical inerrancy, birds were created "on the fifth day". Since there is no reference to the creation of eggs, they presumably were then made by chickens afterwards by the normal process. Therefore, the chicken came first.

Alternatively, for those who accept the intelligent design form of creationism, Eugene Volokh has noted that "In my experience, most creationists are also pro-life -- in which case, the egg is a chicken."