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The chicken and her egg.

M. M. van de Pitte's recent study of ornithology exposes the tenacity of certain unfortunate Aristotelian attitudes toward the female body, sometimes manifested in scientists' simple yet profound inattention to female biology. Van de Pitte's paper reminded me of a dispute in this journal which revealed a similar, if more forgiveable, inattention on the part of philosophers.

In response to Teichmann's article (1991) proposing that the chicken-and-egg problem is no problem since "chicken" is a Sorites term (permitting us to say both that no chicken is born of non-chicken and that chickens have not always existed), Sorensen argues that the chicken egg must have come before the chicken because "a particular organism cannot change its species membership during its lifetime" (Sorensen 1992, p. 541). Thus, even if we cannot say which animal was the first chicken, we can say that the first chicken must have come out of the first chicken egg. He is not dissuaded by the fact that "chicken" is a vague predicate, for "indeterminate states can be determinately related"--for example, although we can never say with precision when either the father or the son first goes bald, it is certain that the father goes bald before the son (ibid.).

Sorensen's general principle is correct, but he goes wrong in its application by confusing eggs with embryos. The resulting analysis dissociates the chicken from the product of her own physiology. Here I will make the case for the general principle that female animals are the sole authors of their own eggs. Such an argument depends not only on conceptual analysis but on the particulars of female biology, especially oogenesis and embryonic development. If my argument is sound, it follows (more modestly) that no chicken egg is laid by a non-chicken (in nature, at any rate), and so the chicken must have come first (even if there is no fact of the matter as to which animal is the first chicken).

The word "egg" is commonly used to refer to two things:

(1) a germ cell, the female reproductive cell containing in its nucleus

a haploid (half) set of chromosomes;

(2) the larger spheroid object, usually white, that is found in nests (of

birds, reptiles, and monotremes) and refrigerators. This latter object

might (but need not) contain an embryo, which will have

begun as a simple zygote, the fusion of the gametes (the male's

sperm cell and the female's germ cell).

Since a germ cell is the product of oogenesis (the process of germ cell development, which begins during the female's own embryonic state), the first definition implies that all and only eggs laid by chickens are chicken eggs.

Under the second definition, the fact that the larger, white, spheroid object is laid by a chicken will be both necessary and sufficient (in nature if not in laboratories) to establish it as a chicken egg. Consider the following two facts.

First, the embryonic stage of any bird bears no causal relation to the gross structures of its own egg, such as the yolk, albumin, and eggshell (the yolk of an egg is fully formed before fertilization; the albumin and shell are likewise laid down by the mother's reproductive tract). Whereas the zygote is a product of its mother and father (barring parthenogenesis), the egg in which it will develop is a product of its mother alone (underscored by the fact that if you want to go into the egg business, chickens are a necessity, whereas roosters are optional). Ironically, it is Aristotle who correctly points out that

In its initial stage the embryo develops from part of the egg, and

the rest serves as nourishment for the creature while it is forming.

[Historia Anomalium, 489b]

To call any egg a chicken egg on account of its embryonic passenger is like calling the mother's uterus a chicken uterus on account of its delivering a chicken. Aristotle turns out to be right again when he says

In the case of the animals that are produced oviparously, we

should think of them as having the same relationship to the yolk

as the viviparously formed embryos have to the mother ... for

since the nourishment of the oviparously formed embryos is not

completed within the mother, when they leave her they take a part

of her out with them. [Generation of Animals, 754a]

The second fact to consider relates to the evolution of the chicken egg itself, where what matters is gene expression in the layers, not in the embryos or hatchlings (except in as much as the latter might develop into layers as well). Again, yolk size, composition of albumin, and the texture, color, and size of the eggshell are all expressions of the genes of the animal that laid the egg, not those of the embryo inside it (if such there be).

These empirical considerations suggest that only chickens lay chicken eggs.

Therefore, no matter which of definitions (1) or (2) we appeal to, at least one chicken precedes all chicken eggs.

Sorensen is right to say that a particular organism cannot change its species membership during its lifetime. However, an embryo and its egg are expressions of two different sets of genes, and may be of two different species, under a number of understandings of that term: morphological (the embryo may have significant and novel physical characteristics), ecological (new characteristics might precede a change in niche), or reproductive (new characteristics may affect the organism's ability or tendency to interbreed with the parent population).

Of course, it is exceedingly unlikely that the appearance of the chicken was a radical instance of speciation like those just mentioned. The latter merely underscore the fact that the developmental break occurs not between an organism and its egg, but between an organism and its progeny. Eggs are not progeny.

The chicken-and-egg question has reminded us of one of Aristotle's enduring lessons (if not one to which he displayed perfect fidelity): when attending to empirical matters like chickens and eggs, we in the philosophy business must take care that theorizing does not get too far ahead of observation. Sorensen's attempt to solve the chicken-and-egg problem relies on a simple and atomistic conception of the egg. Embryology fills in the complex relational details, and reminds us that animals born of egg are born of their mother's egg. Still, the analysis offered here does vindicate (and draws inspiration from) the greater moral of Sorensen's paper, which is that indeterminate states can be determinately related. Its application to the present case yields the following result: the chicken came first.

DAVID B. WALLER Department of Philosophy California State University Fullerton, CA 92834-6868 USA


Aristotle: Generation of Animals. A. L. Peck (trans.). Cambridge, MA: Harvard University Press, 1953.

--: Historia Animalium. A. L. Peck (trans.) Cambridge, MA: Harvard University Press, 1965.

Sorensen, R. A. 1992: "The Egg Came Before the Chicken". Mind, 101, pp. 541-2.

Teichmann, R. 1991: "The Chicken and the Egg". Mind, 100, pp. 371-2.

Van de Pitte, M. M. 1998: "`The Female is Somewhat Duller': The Construction of the Sexes in Ornithological Literature". Environmental Ethics, 20, pp. 23-39.
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Title Annotation:response to R.A. Sorensen, Mind, vol. 101, p. 541, 1992
Author:Waller, David B.
Date:Oct 1, 1998
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