Which came first - the chicken or the egg?

My new paper on the "Chicken or the Egg" problem. This paper is available on SSRN. I have discussed this paper with Prof. Jeffrey Barrett of the University of California at Irvine. He is the editor of the journal "Philosophy of Science".

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Murgi ya andaa

Which came first - the chicken or the egg?

Abstract

Evolutionary Theory holds much sway today. In light of the Theory of Evolution, the question of whether the chicken came first or the egg must be examined anew. The question of whether the chicken came first or the egg has been argued by philosophers and thinkers for centuries, and is a long running question in the Philosophy of Science. This paper makes a novel contribution to the field. It argues that, in the sense that the question is usually understood, the answer is unknowable. In this paper, we treat the matter in a novel fashion. We show that the question can have five different interpretations, and each interpretation interprets the original question quite differently. We further show that the answer to the question is unknowable in the sense that people often interpret it ("Which came first -the chicken or an egg containing a chicken?"). The methodology of the answer to this question – from the purview of the Theory of Evolution – is fundamentally different from arguments from Creationism as well as arguments by philosophers such as Aristotle and Plutarch.

1. Introduction

Philosophers have been puzzled by the question of whether the egg came first or the chicken from ancient times. Aristotle attempted to answer this question. Citing Wikipedia, which although not the most trustable source, is correct in this case [1]:

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." [2,3]

What is obvious from a modern view-point is the missing piece in Aristotle's analysis : a factoring in of the Theory of Evolution.

Plutarch also dealt with this question.

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..." [4,5a,5b]

Again, it is clear what is the missing piece: a factoring in of the Theory of Evolution.

It is pointless to deal with more examples of this discussion from the Ancients because many of them had no sophisticated understanding of how species evolve. A modern answer to this question came from Roy Sorenson, who argued that it was the egg that came first. [6].

2. The scientific explanation

In light of the Theory of Evolution, there really is a perfectly good response to this question - scientifically speaking - the question can be interpreted in certain ways. The answer can be “the egg” or “the chicken”. But, in a certain other way, the surprise answer : it is unknowable.

There are five ways to interpret this question.

1. Which came first - the chicken or the egg (any egg)?
2. Which came first - the chicken or an egg containing a chicken?
3. Which came first – the chicken or an egg laid by a bird that we can call a chicken?
4. Which came first – the chicken, or an egg laid by a bird that we can call a chicken and one that contains a chicken?
5. Which came first – the chicken, or a thing laid by a bird that can later be called a bona fide chicken egg, even if it was not one originally?

If you are asking whether the egg as we understand it came before the chicken, it is clear that it was the egg (Q-A1). This is because there were eggs for various species such as dinosaurs before chickens or proto-chickens ever came to be. The fossil record is replete with examples of non-chicken eggs arising well before there were any chickens.

Now, if you are asking whether the chicken came first or an egg containing a chicken, that makes it a bit more interesting (Q-A2). Indeed, there are other ways to intrepret this question ("Which came first - the egg or an egg laid by a chicken?", "Which came first - the egg or an egg laid by and containing a chicken?", etc.), but let us think about this question first. The egg probably came first in the sense that the first thing that could be labeled a chicken must have arisen out of something that was not quite a chicken. But that is not all.

2.1.1. Set definitions

Let set C be defined to be such that it contains the set of all animals that are chickens.

C = { x | x is an animal and x is a chicken }

Let set D be defined to be such that it contains the set of all animals that are proto-chickens.

D = { x | x is an animal and x is a proto-chicken }

We define a proto-chicken as a creature that is not a chicken but has a offspring that is in set C.

2.1.2. Which came first?

Let us view these sets carefully. It is clear that some of the animals in set D laid eggs that were chickens. So it was probably the egg containing a chicken that came first. Out of these eggs hatched chickens.

I would like to note that this argument is novel because it rests its conclusions on probability. And this is one key aspect of this argument that seems to have escaped the attention of both Stephen Hawking and Chris Langan. Note the use of the word "probably' above. I will come to that in a bit.

Now, it must also be noted that the notion of a species - per the Theory of Evolution - itself is a bit fuzzy. Since eggs and birds co-evolved, they became that thing called a chicken at about the same time.

Furthermore, there are many different ways to interpret this question. Chris Langan tried to treat this question in his answer to the question on his webpage, and gets into some of the details of the problem.

The question “which came first, the chicken or the egg?” looks at first glance like a matter of straightforward reproductive biology. But before we can even begin to answer this question, we must define our terms. So actually, it is a classic case of semantic ambiguity…a problem of meaning and interpretation. Specifically, while the term “chicken” is biologically unambiguous – we all know what a chicken looks, sounds and tastes like - the term “egg” is somewhat more general and is therefore a possible source of ambiguity. Do we mean (1) just any egg, or (2) achicken egg? And if we’re talking about a chicken egg, then is a “chicken egg” (2a) an egg laid by a chicken, (2b) an egg containing a chicken, or (2c) both? Reformulating the question to reflect each possible meaning of “egg” leads to four distinct versions of the chicken-or-egg question.[7]

1. Which came first, the chicken or (just any old) egg?

2a. Which came first, the chicken or an egg laid by a chicken?

2b. Which came first, the chicken or an egg containing a chicken?

2c. Which came first: the chicken, or an egg laid by and containing a chicken?

Contrary to popular belief, there is indeed a definite answer to each of these questions. Specifically, the answers are: (1) The egg. (2a) The chicken. (2b) The egg. (2c) The chicken. Given some knowledge of logic and biology, these answers are not hard to verify. To get this show on - or should that be across? - the road, let’s go through them in order.

First, consider question 1: which came first, the chicken or (just any old) egg? This question is answered “the egg” because species that lay eggs have been around a lot longer than modern chickens. For example, we have plenty of fossil evidence that dinosaurs laid eggs from which baby dinosaurs hatched, and dinosaurs predate chickens by millions of years. Indeed, a growing body of research indicates that dinosaurs were among the biological ancestors of chickens!

Now let’s look at question 2a: which came first, the chicken or an egg laid by a chicken? The answer to this question is “the chicken” on semantic grounds alone. That is, if a chicken egg must be laid by a chicken, then before a chicken egg can exist, there must by definition be a chicken around to lay it. And question 2c - which came first, the chicken or an egg laid by andcontaining a chicken? - is answered the same way on the same grounds; logically, the fact that a chicken egg must be laid by a chicken precedes and therefore “dominates” the (biologically subsequent) requirement that it contain a chicken. So whereas we needed paleozoological evidence to answer question 1, questions 2a and 2c require practically no biological knowledge at all!

The arguments advanced by Chris Langan are generally sound, but not entirely accurate. This is because genetic mutations can occur due to many factors. It is not possible to know exactly which factor was responsible in the case of the chicken. Thus, the answer to the question is: it is unknowable. A further discussion of this is reserve for Section 3. The correct answer, in my view, to the original question Q-A2 is the following:

(1) There is no definite way of knowing. The answer is unknowable.

(2) The probability is very high that the egg came before the chicken per the Theory of Evolution. This is because a proto-chicken is much more likely to accumulate enough genetic mutations to give rise to a chicken than a proto-chicken is likely to acquire enough somatic cell mutations to become a chicken.

Note that the answer to this question is : it is, in principle, unknowable.

The fifth question has some interesting aspects as well. The thing laid by a bird that can later be called a bona fide chicken egg may not have been a chicken egg originally, but may have become one. Now, if we agree that it does not matter what the egg contains as long as it can give rise to something in Set C, then this question gains new, interesting aspects. The proteins and other constituents in this thing may not quite constitute a chicken egg per se, but rather a combination of a chicken egg and a proto-chicken. Nevertheless, since it gives rise to someting in Set C, it is, for the purposes of A5, something that should examined in terms of whether it gave rise to a chicken or not.

Note again that, here also, it is not possible to know – if we are thinking about it rigrously as philosophers of science. (See Section 4 for additional details). Thus, question A5 can be answered as follows:

(1) There is no definite way of knowing. The answer is unknowable.

(2) The probability is very high that this half-chicken-half-proto-chicken-egg came before the chicken per the Theory of Evolution. This is because a proto-chicken is much more likely to accumulate enough genetic mutations to give rise to a chicken than a proto-chicken is likely to acquire enough somatic cell mutations to become a chicken.

Note again that the answer to this question is : it is also, in principle, unknowable.

3. Simulation Study
4. 3.1. Chris Langan's Questions and my answers
5. Let us first go back to the four variants of the question as posed by Chris Langan. The answers to the four variants of this question as posed by Chris Langan are, in my opinion, as follows:

1. Which came first, the chicken or (just any old) egg?

Here, the answer is clear. It is the egg. There were eggs laid by various animals well before there were any chickens.

2a. Which came first, the chicken or an egg laid by a chicken?

Here, the answer is clear. It is the chicken. This can be argued based purely on logic. If the egg had to be laid by a chicken, then the chicken must have come before the egg.

2b. Which came first, the chicken or an egg containing a chicken?

This is the question that was dealt with in the discussion above (Q-A2). The answer to this is : it is unknowable.

2c. Which came first: the chicken, or an egg laid by and containing a chicken?

Here also the answer is clear. It is the chicken. This can be again argued based purely on logic. If the egg had to be laid by a chicken, then the chicken must have come before the egg.

3.2. Analyzing the answer on Wikipedia

In this section, we ask if these conclusions are warranted. We support our arguments by means of a simulation study. Before we come to the simulation study, let us look at the answer to the question as posted in Wikipedia.

The theory of evolution states that species change over time via mutation and sexual reproduction. Since DNA (deoxyribonucleic acid) can be modified before and after birth,[16] 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. However, whether this was defined as a chicken egg or proto-chicken egg is debatable. So technically the egg came before the chicken, but the chicken may have come before the chicken egg. So it depends on whether the question is "What came first, the Chicken or the egg" or "what came first, the Chicken or the Chicken egg".

Logically the final conclusion can be drawn that the egg indeed came before the chicken, as a bird that was not a chicken could accumulate germline mutations in a single sperm or ovum to produce the first genetically identifiable chicken, but a non-chicken egg is much less likely to produce a non-chicken which accumulates enough identical somatic cell mutations across its cells to create a chicken spontaneously.[1]

The main issue with the Wikipedia answer is the following: every animal in question is either a chicken or not a chicken. Let us denote by CS the set of all animals that are chickens. That is, if the animal in question is not a chicken, then discard it from the set CS. Now, find the first ever such animal that was born. There must have been a first (or if they were twins, then multiple firsts.) This is the first chicken. Now, do we really know whether this first chicken arose as a result of a non-chicken accumulating enough somatic cell mutations (this could, in theory, have occurred/be due to a gamma ray striking an egg causing it to mutate after it has started multiplying – at which point it is no longer an egg but something between an egg and a chicken)? No. Do we really know whether this first chicken arose as a result of a non-chicken accumulating enough mutations in a single sperm or ovum to produce the first genetically identificable chicken? No. Thus, it is clear that the answer to the question is unknowable.

3. Simulation Study

In this part of the paper, we would like to present some results from a simulation study.

The simulation study was run as follows. Assume that there is a set of N (N = 10, 20, 30, ..., 100, 200, 300, ..., 1000, 2000, 3000, ... etc.) birds. Consider a new bird C_i that was born from this set of birds. Assume that each bird C_i could have arisen because one of its parent acquired a germline mutation in a single sperm or ovum, and that the probability that it is not an exact copy is p1 < 100% (p1 is assumed to take various values) (G-mutation). Assume that the probability that each bird C_i could have arisen while acquiring a mutation after it started dividing is q1 < 100% (D-mutation).

Next let us assume that this population of N birds is a stable population, that is, each subsequent generation also has the same number of birds. We aim to analyze how many birds in subsequent generations have arisen due to :

• a G-mutation
• a D-mutation
• both

We simulate this scenario in Java. The results of the simulation are presented in Table 1 and Table 2. We use the values for p1 of 99% and for q1 of 2%.

Table 1

XNUMBER OF G-MUTATIONS IN GENERATION #X OF MALESNUMBER OF G-MUTATIONS IN GENERATION # X OF FEMALES100299398920100010002510001000

Table 2

XNUMBER OF D-MUTATIONS IN GENERATION #X OF MALESNUMBER OF D-MUTATIONS IN GENERATION # X OF MALES1002241320100010002510001000

By the first generation, most individuals have acquired one or the other mutation (since the probability of p1 is so high). By the second generation, all individuals have acquired the G-mutation. This is not totally surprising.

What is surprising, however, is that even with a relatively low probability of the D-mutation surviving (only 2%) to the next generation, the D-mutation eventually proceeds to infiltrate the entire gene pool.

By the eight generation, there are only 97 out of 1000 male individuals with only the G-mutation. The other 903 individuals have both mutations. Similarly, out of 1000 female individuals, 877 individuals have the D-mutation. Only 123 individuals don't. By the 12-th generation, virtually every individual has the mutation. By the 25^th generation, the entire gene pool has acquired the genetic mutation.

What this demonstrates is that a genetic variation, although infrequent, can easily infiltrate an entire gene pool. The basic argument of this paper is therefore underscored by this simulation. That is, even if there is a small chance of a somatic mutation, that having contributed to the development of the chicken cannot be overuled. Thus, the answer to the question marked A2 is that it is unknowable.

4. Conclusions

The answers to the five variants of this question as posed by me are as follows:

1. A1. Which came first - the chicken or the egg (any egg)?
2. Answer: the egg
3. A2. Which came first - the chicken or an egg containing a chicken?Answer: The answer is – in principle - unknowable, but the probability is high that it was the egg.
4. A3. Which came first – the chicken or an egg laid by a bird that we can call a chicken?
5. Answer: The chicken.
6. A4. Which came first – the chicken, or an egg laid by a bird that we can call a chicken and one that contains a chicken?Answer: The chicken.
7. A5. Which came first – the chicken, or a thing laid by a bird that can later be called a bona fide chicken egg, even if it was not one originally?
8. Answer: The answer is – in principle - unknowable, but the probabilityis high that it was the egg.

We would like to conclude by making an argument for science.
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The Old Testament view would be that God simply created these creatures out of thin air and thus, the chicken was the first to arrive. It will be seen that this idea is, in fact, entirely false. In the same way that the ideas of Aristotle and Plutarch have given way to new ideas, the idea of Creationism must give way to new theories and principles.

References

(1) Wikipedia, "Chicken or the egg", http://en.wikipedia.org/wiki/Chicken_or_the_egg

(2) Blavatsky, H.P. (1877). Isis Unveiled. pp. I, 426–428

(3) François Fénelon: Abrégé des vies des anciens philosophes, Paris 1726, p. 314 (French). Translation: Lives of the ancient philosophers, London 1825, p. 202 (English)

(4) Plutarch (1976). Plutarch's Moralia: Table-talk : Books I-III. Heinemann.

(5a) ^ Renaud, Gabriel (2005). Protein Secondary Structure Prediction using inter-residue contacts. pp. 71.

(5b) ^ Pluatarch, Moralia, ΣΥΜΠΟΣΙΑΚΩΝ ΒΙΒΛΙΑ Θ, ΣΥΜΠΟΣΙΑΚΩΝ ΒΙΒΛΙΟΝ ΔΕΥΤΕΡΟΝ, ΠΡΟΒΛΗΜΑ Γ: Πότερον ? ?ρνις πρότερον ? τ? ??ν ?γένετο, 635e-638a

(6) Roy A. Sorensen. 1992. “The Egg came before the chicken”. Oxford University Press

(7) Christopher Michael Langan (2001). "Which Came First...". Cognitive-Theoretic Model of the Universe. megafoundation.org. Retrieved 2008-02-08.