The Dope on Eggs
Anisogamy, Science Journalism, and Other Food for Thought
Outside, February 1988
Reprinted from THE BOILERPLATE RHINO: Nature in the Eye of the Beholder (2000) by permission of Scribner, a Division of Simon & Schuster.
MONDAY AFTERNOON of a fresh new week and here's a grown man, damn near forty years old, college graduate, stalking the upper floors of a university library with a notebook in one hand, a sheaf of photocopied pages in the other, and the pinched worried ruthless countenance of a starving coyote. The clock is running. He is a magazine columnist working on deadline, poor fool. His monthly mandate is to demonstrate that evolutionary biology, theoretical ecology, and the incisive contemplation of nature can provide piquant entertainment for people in dental waiting rooms.
As usual, he's three weeks behind. The subject this month is eggs. Eggs, yes, as in chickens and zygotes and nature's ultimate self-contained package for a developing embryo. His notebook is full of scribbled citations and call numbers; his brain is full of eggs. He scowls at the nattering undergraduates in designer denim and moves briskly among the stacks. He knows a few facts about eggs. He knows that the ostrich lays an egg weighing more than three pounds, with a shell strong enough to support the weight of two men. He knows that a starfish can produce forty million eggs in a year. He knows that a marsupial frog carries her eggs until hatching in a pouch on her back. What he doesn't know is how these amusing and utterly disconnected facts can be garbage-compacted into a single essay. Sometimes, and this is exactly such a time, he feels that he has the most ridiculous job in America.
The sheaf of pages is a monograph from the Journal of Theoretical Biology entitled, "Why Are There So Many Tiny Sperm?" It's exactly the sort of scientific question that commands his attention. The week is young and he is still hoping to follow a logical trail on a gentle meander through meadows of biological fact to a neat little conclusion. At this point he is scouting for spoor. Where there are sperm there must also be eggs, correct? After an hour of dashing around the library, though, he can't remember just how this article got into his hand. Nor why. Something he does know is that the wandering albatross lays only a single-egg every two years. He knows about egg-care behavior in the maternal octopus. He knows a thing or two about yolk.
And he has begun gathering a mental list of other eggy questions. Mere facts are no good to him unless they answer (or can be made to seem to answer, or can be twisted and wrenched and piled into odd shapes until they hint at being somehow perhaps on the verge of answering) a question that someone might conceivably want asked. What are the major unanswered egg questions? he has been wondering.
Of course there's the obvious one: Which came first, the chicken or…? But that's not really unanswered, since anyone except a creationist knows that the first egg preceded the first chicken, in the evolution of life, by dozens of millions of years. A better question is, Why does a duck-billed platypus lay eggs, whereas a hammerhead shark or a rattlesnake gives birth to live young? And another, closely related: If some species of reptile lay eggs and some species don't', if some fish do and some don't, if some mammals do and some don't, why is it that every bird species on the planet lays eggs? Now we're cooking, he thinks. There are more. Why do some eggs hatch before being laid? How does a vulture, on a low-calcium diet, come up with enough calcium for its eggshells? Does an egg need to breathe? Does an egg need to drink? How does an egg know when to hatch? Then suddenly he is visited by a question possessing such promising scientific depth and such a stupid surface that he wishes immediately he hadn't thought of it: If we eat chicken eggs for breakfast, why don't we eat chicken sperm?
He doesn't know the answer. Maybe it's a matter of theoretical biology, maybe just good taste. Maybe the difference is packaging. With any sort of luck, this week, he will be able to leave that one unasked.
Down a corridor between the stacks he happens upon his chum the dinosaur paleontologist, seated cross-legged on the carpet like an angry janitor drinking wine, after hours, from a paper bag. On the paleontologist's lap is a heavy green volume. This paleontologist holds an international reputation for his discoveries and analyses of nests full of dinosaur eggs, and today he is browsing for ideas among the books on bird biology.
"What are you up to?" the paleontologist asks our man.
"What about 'em?"
"Anything. I'm open to suggestions."
The paleontologist rolls his eyes pityingly. Then he points to a sentence on the open page of his fat green book. It says that the newly hatched young of the echidna (an egg-laying Australian mammal, related to the platypus) possesses an egg tooth. An egg tooth is a temporary structure that shows up on the beaks of some hatchling reptiles and some hatchling birds, used by the weak little animal to bust its way out of the shell. The occurrence of an egg tooth in this weird mammal represents an interesting primitive trait, says the paleontologist.
"Gimme," says our fellow, and snatches the green volume to scamper off for a photocopy.
He knows that a tapeworm can release two billion eggs in its lifetime. He knows that a parasitic insect called the sheep ked, on the other hand, can expect a lifetime fecundity of only twelve eggs. He knows that the yolk of a hen's egg is rich with two kinds of protein (ovovitellin, ovvolivetin) that will serve as construction material for an embryo chick, and with fats that will gather like creosote in the arteries of a human. He knows that an alligator incubates her eggs in a cozy pile of rotting compost. And now he knows that baby echidnas have egg teeth. He is frantic.
He feeds the word eggs into the computerized periodical index and the computer chortles at him condescendingly, as though to say, Can't help you if you're so vague, you dumb-ass. He photocopies a few scattered pages from back issues of a few scattered journals--Science, Science News, Natural History, Business Week--and grabs an armload of books. By this time he knows why NASA planed to send thirty-two eggs into space (evident on board the Challenger, alas) and what the distinguished food writer M. F. K. Fisher thinks of scrambled ostrich. He knows about the optimal-egg-size theory, never mind what that is, and that a recent study of freshwater turtles tends to refute it. He knows that the male of the emperor penguin stands around for nine weeks on the Antarctic ice holding an egg on the tops of its feet.
He has also found a good concise definition, praise God, for the entity at issue: "Fundamentally, the egg is comprised of a minute center of life, about which are accumulated relatively enormous amounts of inanimate food substances, the whole enclosed in protective structures. Given the proper combination of circumstances, the living fraction of the egg is activated and transforms the nonliving mass into an organism capable of independent existence." This comes from a book called The Avian Egg, but he knows that it applies just as well to the eggs of grasshoppers, snails, giant squid, corals, crocodiles, fish lice, dogwhelks, echidnas, water fleas, trout, and some species of algae. He leaves the library, well informed and utterly hopeless.
It isn't too late to veer off toward a different subject. No one will ever know that he wasted a day on eggs.
By Tuesday afternoon it is too late. He has devoted another half-day to filling his brain with intriguing kibble. He knows that cliff-nesting birds called guillemots lays eggs that are tapered sharply, like chicken croquettes, so that they roll in tight circles and are less likely therefore to go wheeling off a narrow ledge. He knows that maternal earwigs spend great effort keeping their eggs licked clean of fungi. He knows that the eggs of the crested cuckoo have an extraordinarily thick shell, evidently ad adaptation to the fact that the cuckoo drops her eggs rather rudely, for foster rearing, into the nests of other species. He knows that corals of the Great Barrier Reef indulge in mass orgies of synchronized spawning. Much of this kibble comes out of a book titled Eggs: Nature's Perfect Package, from a publishing house that calls itself Facts on File. He is grateful to the author, Robert Burton, and would also very much like to strangle him, since the book is full of information but offers virtually no footnotes or bibliography. Nothing can be traced to its scientific source. The FCC or someone should require that this publisher rename itself Facts Adrift. He knows from Mr. Burton's book that certain scientists have discovered prehatching communication among eggs of the bobwhite quail (mutually audible tapping, like in Darkness at Noon), but he doesn't know which scientists announced such a discovery, or when, or where.
On Wednesday morning his editor calls from Chicago, sounding cheerful. "How's the column coming?" His editor is a young man of saintly equanimity who has consented over the years to publish all manner of creep-show biological comedies and whose sole demands seem to be decent grammar and promptness.
"Fine," our man lies. "Pretty good. I think you'll have it by Friday. Is Friday OK?"
"Uh. All right, sure. Friday's OK."
"In that case, how's Monday?"
He knows of a certain Black Orpington hen that once turned heads by laying 361 eggs in less than a year. He knows that the common mussel can deliver itself of twelve million eggs in fifteen minutes. He knows that these two beasts belong side by side in the Guinness Book of World Records but not in any coherent science essay that he can so far imagine himself writing. He knows the difference between isogamy (sexual reproduction in which all the sex cells, or gametes, are of similar size) and anisogamy (sexual reproduction in which some members of the species produce big passive gametes containing nutritional supplies, while other members of the species produce tiny fast-moving gametes containing only genetic information), and he knows that those two types of anisogamous gametes go by the names egg and sperm. He senses now that in the mystery of anisogamy lies the answer to at least one of the great eggish questions. He is not sure he knows which one.
He has been back to the library three times, he has photocopied from the Journal of Theoretical Biology a half-dozen more monographs on the subject of anisogamy, and as a hedge against desperation, he has phoned the manager of a local chicken ranch. Yes, the manager will give him a tour tomorrow.
Now it's late Wednesday night, and our egg guy has begun decoding the anisogamy monographs. Some of them say things like:
See what I go through for you people, he murmurs silently. Another begins with a sentence so wonderfully scientific that it almost brings tears to his eyes: "Sex has always been an embarrassment to population biologists." These articles originally appeared over a span of ten years, but they seem to be interconnected; the authors are talking to each other, homing in toward the truth about anisogamy. The first article in the series, and the one that seems to have sparked all the rest, was published in 1972 by Parker and Baker and Smith, which sounds more like a double-play combination than a group of scientists. Its title is "The Origin and Evolution of Gamete Dimorphism and the Male-Female Phenomenon," no less. Clearly it's a seminal piece of work.
The gist of this whole packet of monographs seems to be: 1) that the world knows two (and only two) different genders within the realm of sexually reproductive species, which two genders produce two (not one and not three, not four, not twenty) different relative sizes of gamete, a large slow size containing a nutritional legacy for the future youngster and a tiny quick one containing genetic instructions only; and 2) that the world knows these unremittingly binary circumstances for a small number of reasons comprehensible in the terms of theoretical biology, among which reasons are the factor of competition among galloping herds of sperm, the improbability of two overstuffed eggs being able to locate each other for sapphistic union in an ocean of loneliness, and the fateful fact that f31x1+f32x is less than or equal to W. Our man on the egg beat now recognizes the whole thing for a fascinating scientific question that might lend itself rather well to vulgarization and mockery, but unfortunately by this time his column is nearly written and there's no space left for doing justice to anisogamy and it's time he departed for his tour of the chicken ranch.
Cherry Lane Farms consists of six huge metal sheds and a processing building on the outskirts of Three Forks, Montana. It is the workplace of 150,000 assiduous leghorn hens and the amiable man charged with their supervision, Don Zeiger. Mr. Zeiger has been in the business nine years. Mr. Zeiger likes eggs. "Well, yeah, let's see. I had four for breakfast this morning in Helena. Had four yesterday morning. And I'll probably have six for supper." Each week Mr. Zeiger ships about 900,000 eggs and eats about three dozen.
No, says, Zeiger, there isn't a rooster on the place. He doesn't breed his own stock. He buys young hens from breeder farms in Iowa and Minnesota, keeps them for an egg-laying career of roughly two years, then ships them back to a slaughterhouse that is also in Minnesota. Throughout their time in Montana, the hens lay hard, live a claustrophobic but otherwise decent existence, and get one ten-week vacation. During the vacation they molt. Unlike some chickens raised purely for meat, they are allowed to keep their beaks and their feet and their combs. The combs on these hens are long and red and floppy. Cutting the combs, says Mr. Zeiger, is bad for morale.
A young hen with good morale lays about six eggs per week. As she gets older, her eggs tend to be fewer and bigger.
Inside one of the henhouses, the egg journalist looks upon rows of cages stretching away to the vanishing point. He breathes an atmosphere thick and sour with he prefers not to imagine what. He peers down one narrow corridor between those rows of cages, and hundreds of white heads with floppy red combs lean out to peer back at him. A single egg drops to the floor of one cage, rolls forward gently through a low slit, and comes to rest in a trough. All right, who was that?
"Mr. Zeiger, I want to ask you a question. I'm coming at all this from a scientific angle, remember. I hope you won't take me wrong."
"OK," says Don Zeiger.
"Have you ever wondered why we eat chicken eggs, but not chicken sperm?"
Of course it's because of anisogamy. It's because one contains food, the other contains only information. The question is not really trivial, or disgusting, or ridiculous.
"No," says Don Zeiger. His fleshy ranch-manager face softens with the faintest twitch of a smile. "No sir, I never have."
The man with the notebook nods. He changes the subject. What he would like to be able to say is "Neither have I."