In the Beginning
THE SCIENCE of immunology is barely Too years old, but the processes it deals with are as old as the earth itself. The way in which our bodies fight infections evolved along with the oceans and the continents, so that today the antibodies that patrol our circulation, the white cells that guard our tissues, are as fundamental as the rocks we walk on and the air we breathe. end of all that had gone before and might have come after.
There is an idea most of us share, that whatever it was which began in that distant time was a very fragile thing. It is a notion nourished by our humanity and our fears, but also fostered by science itself, which conjures up the view that life is a delicate mechanism, so precariously balanced that even the tiniest insult can shatter it.
Yet whatever it was that happened in those ancient seas has endured. Ages have come and gone, land-masses have shifted, the geography of the oceans has changed, oxygen has permeated the atmosphere, temperatures have risen and fallen and risen again; but through it all, despite its seeming fragility, life has survived and prospered. It has filled the earth and the skies, it exists in the deepest parts of the oceans and clings to the highest mountains.
LIFE‘S beginnings are shrouded in mystery; the miracle that brought it about may be hidden forever. But perhaps the greatest mystery is not life’s beginnings but its incredible tenacity. Life’s endurance, its survival, growth and domination—these are qualities as extraordinary as its birth, and of these we do indeed know something.
The processes that brought life about, and continue to maintain it, started when the newly formed earth had cooled enough for the water, long held in the atmosphere as steam, to condense. Great curtains of rain then began to drench the still-smouldering globe, a continual torrent washing the atmosphere, cleansing it of the billions of tons of compounds that had been formed there, carrying them down into the newly developing oceans.
What came after was a time of struggle, of survival of the fittest. Not the survival of any living creatures—there were none yet—but of what those creatures would ultimately be formed from, the organic molecules. Thousands of different kinds of sugars, hundreds of different alcohols, scores of dissimilar aldehydes, all had been washed down into the oceans, forming in the tidewater areas what has been called the “primeval soup.” The molecules which survived that soup did so because of their stability of construction, the number of atoms in them and the types of bonds holding the atoms together.
These struggles were as ruthless as any battle for survival since; only the strongest made it. Thus the chemical processes which go on in our own bodies—the compounds that make up our metabolic pathways, the sugars and fats that carry our energy, the amino-acids that constitute our proteins, the phospholipids that make up our cell membranes—arc the best compounds that nature, could develop. fluids in our bodies mimic the primeval seas in which we began. The concentrations of salts, of sodium, potassium and chloride in our bloodstream are the same as those that existed in the earliest seas.
We still carry those seas within us, and the same chemical battles that were fought in them some 3,000 million years ago are being waged today in fighting our infections and controlling our illnesses. The battlefields may have shrunk from hundreds of square miles of ocean to a few cubic centimetres of blood, from bays and inlets to the fluids of kidneys and lungs, but failure now means the same as it did then—the some 3,000 million years’ battle for survival.
But survival and dominance meant more than simply continuing to grow, or merely to exist; it meant protecting whatever growth had been won. Indeed, life and protection have always gone hand in hand.
The evolutionary formation of membranes was the first truly dramatic example of this intertwining. Now there was a clear way to divide the outside from the inside. The molecules and enzymes that had been evolving in the open seas somehow enclosed themselves in membranes, and so were assured an environment in which they would always be dominant.
The ancient seas were suddenly and for ever preserved. By the simple expedient of separating tiny parts of the oceans from the whole, of containing these parts within the membranes, their contents were once and for all kept apart from the changing salt concentrations, from the increasing minerals and alkalis, and from the sludge draining off the continents.
Ice ages would come and go, the oceans would fill with materials, the very air would change; and still the ancient seas—inside the cells—would go on and on unchanged, allowing life to develop in an environment to which its parts were already eminently suited.
Once the chemistry of life was firmly protected within the cell membranes, there began the evolution we are familiar with—the development of living creatures—and with it came the beginning of our immune system. For by the time of cellular life, a new pressure had entered those early oceans : the need for food. The cell which could better utilize energy sources to maintain itself would prosper and, in that prospering, dominate the less-efficient cells. The only food source large enough to support life was locked up within the cells themselves, and so evolution took a violent turn.
Feeding began. Whole species devoured the species next to them, only to be eaten themselves in turn. The organisms that eventually survived triumphed not only because of differences in their metabolism—a greater ability to utilize available foods—but because of their aggressiveness and bodily defences.
Those that moved more quickly survived the slower; those that were too sticky to be torn apart continued to exist; those that fought back, that made poisons and chemicals which killed the organisms that were trying to kill them, went on to form more of their own. The battles were no longer for dominance but for sheer existence. And those struggles which began back in those early seas, when the first cell turned on its brother, have never ceased.
We live today as we always have, at the bottom of a sea of bacteria and viruses. Plague, wound infections,
the horror of leprosy, the convulsions of rabies, pus-infected organs, women dying of puerperal fever : it is all one living thing eating another, even as it was in the ancient oceans.
No matter how we may wish to view ourselves, despite all our fantasies of grandeur and dominion, all our fragile human successes, the real struggle has always been between microscopic adversaries, never more than seven microns—less than 0.0003 inch—wide.