by Lyall Watson
Most simple organisms composed of a single cell reproduce by the bacterial method of binary fission in which a parent cell divides into two daughter cells, each containing roughly half the original material. If the cell has a nucleus, this divides first so that each daughter gets an equal share of the organism's hereditary material. Where there are unpaired structures in a cell, such as the single gullet in the small slipper-shaped Paramecium, one of the daughters gets this and the other has to grow its own from instructions contained in its share of the nucleus. Parasitic protozoans, such as Plasmodium, that live in the body fluids of their hosts are protected from the rigors of the external environment and surrounded on all sides by an abundance of food that they simply have to absorb through their cell walls. Under these ideal conditions, reproduction can take place very rapidly. Finding binary fission too slow, these organisms resort to multiple fission in which the nucleus splits rapidly into a large number of parts, each of which becomes surrounded by a tiny piece of protoplasm and becomes a separate cell. It is the shock of this sudden multiplication and the simultaneous emergence of billions of tiny parasites in our bloodstream that produces the fever of malaria. By dividing their assets in these ways, both Paramecium and Plasmodium enjoy the same kind of deathless continuity as the bacteria.
Higher up the ladder of evolution there are many other immortals. One little coelenterata bears the name of the mythical monster Hydra because of its ability to grow a new head or to bud off entirely new individuals from the side of its body. The flatworm Planaria produces two or more complete worms when cut up into pieces in a way that would certainly prove fatal to other species. An arm separated from a starfish soon regrows the four missing limbs and goes straight back into business on its own. Reproduction of this kind is useful to any organism when rapid multiplication is necessary or advantageous, but there is a catch. Every daughter cell and every new bud produces an offspring exactly like its parent. This is fine as long as conditions do not change, but in our dynamic system the advantages go to organisms that can themselves change to keep pace with changes in their surroundings.
Life found the answer to this dilemma in sex. Even while most bacteria were occupied in fission, a few began to experiment with a direct exchange of hereditary material between intact individuals. In 1947 Joshua Lederberg, then of Columbia University (he is now at Stanford Medical School), showed that the common colon bacillus Escherichia coli, which each of us carries by the million, sometimes occurs in two forms that have elementary male and female characteristics. [110] At times an elongated cell from the male strain approaches close to a cell of the plump more rounded female type and extends a short tube that pushes through the cell wall of the female and injects genetic material. This process of transfer takes about two hours, which means that mating in bacteria can last six times as long as a nonsexual generation. It sounds like a pleasant way to prolong life.
The value of the transfer is that cells produced later by the female bacterium have a mixture of male and female characteristics. For the first time in evolution, offspring have two parents and differ from both of them. The adaptive advantages of this development are considerable, and ever since that time, sexual reproduction has played an increasingly important part in the lives of all organisms. For a while it existed alongside the asexual techniques of fission and budding in an alternation of generations, but eventually the advantages of sexual reproduction outweighed those of all other methods, and organisms evolved that were totally sexual.
This meant that they could be either male or female and could only multiply by giving small parts of their bodies to a union that produced new individuals. For the first time organisms really were individuals with a finite life cycle. They were born and grew and reached maturity and reproduced, but then (unlike the bacteria, which just divided and started again) they grew old and died. Death is the price we have had to pay for sex.
As some compensation for loss of immortality, organisms gained individuality. From being merely transitory phases in an endless process, they became discrete entities with their own unique characters. Whereas it was only possible to say of bacteria that a process had been disrupted, the same event in the insect world can be described by saying that a grasshopper has died. With the existence of individuals, it becomes possible to move from the generalization that death occurred to a particular description of exactly who is dead; but a new problem looms. We decided earlier that an organism was still alive despite the fact that some of its constituent cells were dead. We even suggested that the dead cells might validly be considered alive because they still played a role in the survival of the organism as a whole. When individuals belong to a closely knit society, they may have to be considered in exactly the same way.
The zoologist Claiborne Jones points out that it is as difficult to find a satisfactory definition of an individual as it is of a species, and he suggests that the honeybee, for instance, is not an organism at all, but a totally artificial human concept. [132] It is the beehive that exists as an organism. If this is true, then, when a worker bee is killed has it died or is it just one disposable part of the hive that has been lost? There are ample grounds for considering the beehive and the termite nest as organisms in their own right. Individual worker bees or termites are sterile and no more capable of reproducing themselves than red blood cells. In fact, they fulfill identical roles as fetchers and carriers and have as little chance of survival on their own as an isolated blood cell. Who, then, has the individual identity, the bee or the hive? If the hive is the organism, does its life depend on the number of worker components that survive? How many bees can one remove before the hive can be said to have died? It seems likely that the answer to this dilemma is the same as that which applies to cells in a body -- namely, that life and death exist side by side and that a definition of either, if it is to be at all meaningful, will have to include both.
The possibility of social organisms and group identities raises another question. Assume that some disruptive outside force breaks up the hive without killing a single bee, but simply spreads the bees out over the surrounding countryside. The hive has disappeared, but is the organism dead? If not, what do you say when the scattered bees are taken in and become component parts of other hives? If a wolf is killed and eaten by other wolves, we say that it has died, but is this right? The dilemma grows. Where does life reside when its parts are rearranged? This is not just a philosophical problem. With the advent of transplant surgery, it becomes one of major moral and legal concern.
Marine sponges consist of masses of cells organized into a community that functions as a whole and is considered by most zoologists to be a single organism. But if you cut up a sponge and squeeze the pieces through silk cloth so that every cell has been separated from its neighbor, this disorganized gruel soon gets together and reorganizes itself into a complete sponge. A very neat experiment along these lines has been done with the red encrusting sponge, Microciona prolifera, and the yellow sulfur sponge, Cliona celata. [121] A specimen of each was finely sieved and the solutions were thoroughly mixed together. At the end of twenty-four hours, the red and yellow cells had reorganized themselves and become combined back into their original sponge forms. Two distinct living organisms existed at the beginning of the experiment, but who was alive and who was dead in the blended soup? The cells were all alive, but at what stage can we claim individual life for each of the organisms? And what are we to make of the strange fact that a few red cells turned up quite happily built into the yellow sponge?
There is room for argument that sponges are colonies rather than discrete organisms, but Theodore Hauschka has done some extraordinary work with an undoubted organism -- a mouse. [121] He took embryos from a mouse on the thirteenth day of gestation and ground them up small enough to pass through a fine hypodermic needle. This solution he inoculated into the body cavities of virgin female mice of the same strain. After five weeks, all these animals were found to have large co-ordinated masses of bone and
tissue growing in their peritoneal cavities. These masses were identical to those of embryonic mice about one week old. The separate cells were obviously still capable of getting together and growing as if intent on forming complete animals, but which animals? Mice, it seems, but which mice? The same ones that would have been formed in the original uterus? If not, what has become of those mice? Are they dead?
A clue to the whole problem lies in the behavior of individual cells.
Many different types of cell will continue to multiply freely outside the body if given the proper conditions. This technique of tissue culture requires the right temperature and a complex nutrient solution that may contain as many as a hundred different ingredients. Most experts have their own little tricks for getting a culture started. Cells from bone marrow or the lining of the intestine are already multiplying freely in the body, so these stand a better chance of getting a culture going outside. Embryonic cells are also likely candidates because they have already begun to grow rapidly and seem to carry some of this momentum over into new situations.
In recent years isolated tissues have been cultivated from cells taken from ducks, rabbits, cows, sheep, horses, mice, rats, guinea pigs, monkeys, and humans. If the cells come from an embryo, they will often group themselves into an appropriate structure such as a muscle or a bone of the right size and shape for that species. Isolated plant cells can even be coaxed into producing whole new organisms. A tissue culture started from a single cell taken from the growing shoot of a tobacco plant has developed in the laboratory into an entire adult plant complete with roots, leaves, and flowers. Every cell in any organism has this potential. In each nucleus lie all the necessary instructions for producing a fully functional combination of cells in the shape of an individual of that species. No animal has yet been produced in this way, but theoretically there is no reason why it should not be possible to culture hundreds of new individuals, each identical to the original donor.
In practice there is a snag. It is known as the Hayflick limit. Hayflick is a tissue-culture expert working at the Wistar Institute in Philadelphia, where he has discovered that a culture started from human embryonic cells will only continue to multiply for about fifty generations. [30] No matter how good the conditions may be, the culture cannot be persuaded to go any further -- it just dies. Hayflick suggests that this might be a natural limit and that even in the body no cell would be able to do more than this. If we go back to the starting point of the fertilized egg, we can add perhaps another twenty generations, and this total of seventy multiplications would result in sufficient numbers to replace every cell in the body 20 million times. It is true that this is more than enough for any man's life-span, but at the moment there is no evidence that the Hayflick limit applies to cells in their proper place. It is clear, however, that cells in a culture lose some vital factor after a period of growth in isolation. We will see later that this factor has now been identified, and I suspect that with improvements in culture techniques it will be possible to retain or replace this factor and exceed the Hayflick limit.
The most fascinating part of this tissue research is the discovery of what happens to an isolated culture when it nears the present limit. Cells that start off as clearly recognizable human body cells begin to lose their unique identity. After being forced to multiply again and again, without being allowed to produce an organ or structure characteristic of their kind, the cells seem to "forget" who they are supposed to be. The Hayflick limit is different for every species, but the same thing happens to the cells from any organism as they near this point of collapse -- they seem to "lose their memories." After long culturing all cells, regardless of their origins, come to look the same. Highly distinctive units from the salivary glands of fruit flies, from the ovaries of sheep, from the inner ears of mice, or from the petals of a flower all slide into anonymity. They become amorphous squamous cells with no particular shape and no sign of their unique origins or destinies. They become idiots.
These anonymous isolated cells still carry their genetic blueprints, they still feed and grow, their cytoplasm throbs and simmers, and they divide on schedule, but they have become self-duplicating automatons with no special plan. They have lost their identity and purpose and have become totally incapable of fulfilling the potential that still lies encoded in their chromosomes. The plans are intact, they contain all the instructions for life, but the cells have forgotten how to read.
These simpleton cells seem to have reverted to a state something like that of the very first living cells ever formed. They become once again a sort of lowest common denominator, an unspecialized building block capable of going in any direction; but in the exhausted tissue culture they go nowhere -- they just die. There is only one way to save these cells, and that is to give them new instructions. If exiled human cells are fed on a mixture containing horse serum, they become more horselike and go off with renewed energy in this direction. Or if some mutation takes place in one of the cells, a new line with its own momentum takes command and the culture starts to grow beyond the old Hayflick limit. This is what happens when a cell becomes cancerous. It undergoes a mutation that gives it instructions unlike those of its parent cells, and it is no longer subject to their restraint. The tissue takes on a new identity with its own limits, and these in turn can be surpassed with further changes and mutations.
Another way of reviving a flagging culture is to put it back into contact with the body of the original donor. If the cells have mutated in the meantime, they sometimes produce malignant growths or cancers, but if their genetic material remains unaltered, they will often begin functioning once again with all the old vigor. They will work once more toward a particular goal, which depends on their precise location. Cells from the orbital area of a frog embryo can be removed and placed somewhere in its stomach region, but there they produce new gut lining and not internal eyes. There is a co-ordinating system that ensures that cells in a particular area, although each is potentially capable of doing anything, do what is required of them there. If this were not so, a group of cells sparked into activity in any area might produce something totally inappropriate. It would be most alarming if, after a minor cut or abrasion on your elbow, cells started to regenerate in an undisciplined way and you grew a baby there. This is not as outlandish as it sounds because there are species, such as the freshwater Hydra, which do exactly this. The immortals retain a cellular freedom which allows each part to duplicate the whole, but more mortal species are governed in a way that makes the parts subordinate to the general plan.
The co-ordinating centers that enforce genetic instructions are not confined to the brain or the endocrine glands; they have never been isolated in any one part of the body, but seem to be present everywhere. In the case of the tobacco cell that grew into a whole new properly co-ordinated plant, the governor must have been present in the single isolated cell. This could be true of all single cells, and we may, with the proper technology, one day be able to grow any species from any one of its smallest parts. Right now we can only produce small tissues from the isolated body cells of animals, but we have made one vital and far-reaching discovery. The fact that isolated cells eventually lose their biological identity, that they lose touch with life, gives us our first real insight into the nature of life and death.
We have seen that the two states are almost indistinguishable, that they exist together in varying proportions along a sliding scale with no fixed points. We have characterized life as a state of organization and found that patently dead cells often show the same properties. We have eliminated simple self-reproduction as a useful criterion. We have outlined some of the difficulties inherent in trying to decide where life ends and have suggested that it might still be found in some form even in matter that we normally consider to be dead. Now, with the knowledge that cells left too long on their own change from directed living units into disorganized idiots, we have the germ of a theory that seems to fit all the facts.
The Romeo Error is a conf
usion of life with death and is made so often simply because there is no absolute difference between the two. They are manifestations of the same biological process and differ only in degree. There is, however, a third state that is qualitatively distinct from both life and death. This is a state of anonymity of the kind that becomes apparent in cultured cells near the Hayfiick limit. These cells are not alive in the normal sense, because they lack the identity of the species to which they once belonged; but they are not dead, either, because they continue to show many lifelike activities. They differ from live cells in the blood and dead cells on the skin in that they lack the organization characteristic of their species. This absence of a dynamic pattern is the predominant feature of the third state, which cannot be called either life or death, but is a real and recognizable condition in its own right and needs a name. I suggest that for the time being we call it goth .
Apart from its application as a proper noun to an ancient Teutonic race, goth is meaningless in all major languages and is a word that can conveniently keep the same form for singular, plural, adjective, verb, and all tenses.