| SOUL SEARCH (what is this?) A Scientist Explores the Afterlife David Darling 
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Man has given a false importance to death. Any animal, plant or man who dies adds to Nature's compost heap, becomes the manure without which nothing could grow, nothing could be created. Death is simply part of the process.
– Peter Weiss, German dramatist and novelist
Death seems certain and universal. So the shock is all the greater when we find all around us swarms of living things that never show the slightest signs of aging.
Bacteria, for instance, don't grow old in the normal sense. They can be killed by extremes of heat, toxic chemicals, viruses, and the like. But they never succumb to old age. Not for them the creeping senility, inevitable among our own species, as tissues and organs wear out and fail. Bacteria grow, but in growing retain their pristine form and perfectly running cellular machinery – right up to the point at which they neatly divide down the middle and become two.
We are not used to thinking about this kind of reproduction. Conceptual problems spring to mind. If bacteria don't age or die, then exactly what does happen at the moment they divide? In the human world we can keep track of individuals and their parents and offspring. But with bacteria, matters are not so clear cut. When a mother cell divides, the old organism vanishes on the spot, to be replaced by two smaller, genetically identical copies. The parent organism in effect becomes its offspring; those offspring in turn become their own daughters, and so it goes on. The upshot is that, barring any random genetic changes, the family tree of a colony of bacteria has no distinguishable branches or lineages. It just telescopes down to a single anonymous member, an endlessly fragmenting, endlessly rejuvenating progenitor.
Given such a reproductive style, it is hard to say whether bacteria really qualify as "individuals." On the one hand, a single microbe can be isolated and thought of as a creature apart (at least until it becomes two). On the other hand, there is no practical way to distinguish this cell from any of the others in the colony. All are clones. And, when it eventually does divide, where on earth does our supposed individual go?
Such habitually dividing organisms as bacteria are ageless in the sense that they show no signs of deterioration as time goes by. But agelessness is not the same thing as immortality, because to be immortal a creature has to preserve its individuality – its "personal" continuity – in some recognizable form.
Are there any such genuinely eternal life-forms on earth? Probably not, but the best candidates are organisms such as brewers' and bakers' yeasts. These are fungi that multiply by budding, so that the daughter cells are clearly distinguishable and chronologically younger than those of the mother. Since new buds can't form at the site of old bud scars, the mother eventually becomes sterile: after about twenty buddings it is peppered with scars and can no longer bear offspring. Budding bacteria exist, too. The photosynthetic bacterium Rhodopseudomonas palustris seems to sprout daughters with impunity, as do certain bacteria that grow on stalks. All these microscopic budding life-forms show definite mother-daughter relationships in their reproduction. What is not clear is whether the mother, after it ceases to bud, eventually dies. The general assumption is that it does. But, in fact, there is no firm evidence for this and it remains a tantalizing possibility that budding microbes represent the only genuinely immortal beings on the planet.
Back, though, to simple splitting cells. These we can be sure at least are ageless. But why? Human beings age. Virtually every life-form we can see with the unaided eye (the giant amoeba is an exception) ages as time goes by. We grow, our bodies slowly wear out, and we die. So why, if eternal youth is a birthright of the simplest living things, is it so manifestly denied to more advanced creatures like ourselves? Why are human cells, and the complex beings they are shaped into, apparently predestined to die?
Despite all the great strides made by medical science, most of us will be lucky to survive much beyond the biblical three score and ten years. Improvements in hygiene and the treatment of disease have done wonders for the quality of our lives. They have dramatically reduced our chances of an early death through illness. But even in the most developed nations (Japan and Sweden currently head the longevity league), the average lifespan of men and women has yet to rise above eighty. Nor, barring some revolution in gerontology, can we expect any sudden upswing in progress in the near future. Eliminating every major pathological cause of death today, including the three biggest killers, cancer, heart disease, and strokes, would still leave the normal upper limit of human life stuck at around ninety or one hundred years. It is as if each of us harbors a time bomb, primed at birth, that relentlessly marks off the seconds before we die.
We are all composed of cells – roughly 100 trillion of them. But with certain exceptions, most notably the neurons of the brain, the cells making up your body now are not the same as those that were inside you a few years ago. This is equally true of other multicellular organisms. It is an often-repeated "fact" that bristlecone pines and sequoias are among the oldest living things on earth. And in one respect this is true: the eldest of these venerable plants began life well before the Roman Empire reached its heyday. On the other hand, no living cell inside any of these ancient trees today is more than about thirty years old – less than a third of the age of the oldest living nerve cells inside some human beings. So, if we take only living cells as a measure of an organism's age, then it is we, not, the bristlecones, who rank among the world's extreme geriatrics.
As each of our body cells dies, it is replaced by another and that one by another and so on. The trouble is, this process of substitution and replication does not go on forever. The root of the problem was uncovered by the American biologists Leonard Hayflick and Paul Moorhead at the Wistar Institute in 1961. Hayflick and Moorhead demonstrated the reality of a time fuse in man by teasing cells from soft body tissue and allowing them to grow in a culture fluid. Working with human fibroplasts (connective-tissue cells) taken from embryos, they found that there is a definite limit to the number of times these cells will divide. Over a period of months, the cells in each culture divided repeatedly, gradually slowed down in their rate of reproduction, became visibly sick and, after a total of about fifty divisions, died.
Later experiments showed that normal cells apparently have a mechanism somewhere inside the nucleus for remembering the number of times they have divided. What is more, this "memory" survives even in cells that have been stored for long periods at very low temperatures in liquid nitrogen. Frozen at the twentieth doubling, for instance, the cells undergo thirty more doublings after being thawed, and then stop. Frozen at the tenth doubling they oblige with forty more, and then die. Always the total is around fifty. One particular strain studied by Hayflick kept accurate count of its number of doublings even after being stored for more than thirteen years at -190°C.
No exception has yet been found to the rule that normal cells have a finite capacity to divide, as measured by the so-called Hayflick limit. In other animals, the limit is different: about twenty in the mouse, twenty-five in the chicken, and 110 in that most long-lived of vertebrates, the Galapagos tortoise. The longer the natural lifespan of the organism, the higher its Hayflick limit – which seems reasonable. Less obvious is why there should be any restriction at all on how many times a normal cell can reproduce.
Intriguingly, this doubling limit does not apply to certain other types of cells. Cancer cells and germ-line cells (egg and sperm) in particular appear to be immune to aging. These are the jokers in the pack; both types can and do divide endlessly without showing any signs of wear and tear. A cancer looks abnormal and divides abnormally: chaotically and dangerously. A normal cell infected with a cancer-causing virus, as Hayflick showed, becomes cancerous and will subsequently divide without limit in a maintained laboratory culture. It seems ironic that for ordinary animal cells to aspire to immortality they should have to take on some of the very properties that would cause the eventual demise of their host organism – and, therefore, of themselves.
Egg and sperm cells, too, have the potential for immortality, a fact first noted as long ago as 1885 by the great German biologist August Weismann. Weismann drew a clear distinction between what he called the human "germ-plasm," the chromosomal material involved in reproduction, and the rest of the body, or "soma." In the light of this distinction, we can think about the problem of the origin of death in another way. That is, why has nature engineered a fundamental difference between cells that are ageless and those that form a mere temporary and disposable receptacle? Obviously, if we and other organisms never died, evolution would have been impossible, and we would not be here to ponder the riddle of our own mortality. But that is an argument based on hindsight. We need to avoid the suggestion that nature somehow had it in mind all along to make complex throwaway life-forms. Biological evolution, blind and undirected, simply doesn't work that way.
Instead, we need to seek out the origins of human mortality at a molecular level. The secret of the birth of death almost certainly lies among the tangled braids of that peculiar and unique substance, deoxyribonucleic acid – DNA. One of the outstanding achievements of twentieth-century science was the elucidation of DNA's molecular structure. The now-familiar double helix arrangement of DNA resembles nothing so much as a twisted rope ladder. The rungs consist of chemicals, known as amino acid bases, which are code named A (for adenine), G (for guanine), T (for thymine), and C (for cytosine). These bases are effectively the four letters in the alphabet of life. Just as we use the twenty-six letters of the English alphabet to construct specific messages and meanings, so nature casts the four amino acid bases into sequences that carry specific biological information. Genes are simply long lists of instructions rendered in the four-symbol alphabet of DNA, each gene specifying the design of a particular product, usually a protein.
The bases that compose these genetic messages have a very special property which is at the core of life on Earth – they always pair in the same way, A with T, and G with C. As a result, the rungs of the DNA ladder consist of A-T and G-C pairs. Crucially, these pairs are structurally interchangeable so that, for instance, a C-G pair can substitute for an A-T pair without disturbing the shape or stability of the DNA spiral. Holding each rung together at its midpoint is a weak chemical bond (a hydrogen bond) that is easily broken when the time comes for the DNA to divide and unravel into separate strands.
During cell division, when the double helix of DNA peels apart, two copies of the original genetic message are created. Although equivalent, these copies are not identical. One is the complement of the other, just as a mold and a cast contain the same image but in inverted forms. For example, if the base sequence on one side of the divided DNA ladder is AAGCTATCCG, the sequence on the complimentary side will be TTCGATAGGC.
Imagine that, for some reason, a mistake creeps in during the copying process. A G, say, couples with an A instead of a C. Now, after the partner strands have separated following replication, one strand will have the correct base (G) and the other a mistake (A). Because the coupling rules are extremely unlikely to be broke twice in succession, the outcome of the next round of copying is almost inevitably one offspring DNA with a (correct) G-C pair and one with an (incorrect) A-T pair. At first sight, it seems as if this mismatching might have disastrous consequences, perhaps throwing the whole DNA molecule into disarray. However, since the A-T pair has the same basic symmetry as the G-C pair, each new DNA will preserve the original 3-D helical format. An error has found its way into the code but the architecture of the code's carrier, DNA, remains uncompromised.
In DNA, alone among known copying machines, order is preserved in the face of random mistakes, not destroyed by them. Yet the ceaseless editing and proof-reading needed to root out occasional duplication errors do not come free. They take up a sizable slice of the cell's total energy budget. Further energy has to be channeled into keeping the cell's life functions running smoothly. Damaged proteins must be quickly tracked down and disposed of before they can wreak havoc; energy has to be diverted to the machinery that monitors the efficiency of the cell's protein-making processes, and so on.
Primitive, one-celled creatures such as bacteria can easily come up with the energy required for damage control, because they are genetically and functionally simple. But with bigger and more elaborate organisms, maintaining error-free copying is more of a problem. The trouble is that tying up too many resources in genetic error-checking makes the creature less viable in other ways. Little is to be gained from having a high-accuracy body if it is defenseless against low-accuracy, short-lived predators. In any case, argue biologists Thomas Kirkwood of the Medical Research Council in London and Richard Cutler of the National Institute on Aging in Baltimore, why waste energy trying to preserve immortality when an individual is likely to be killed by environmental hazards within a fairly short and predictable period anyway? From nature's point of view, it makes more sense to invest in protective systems that ensure youthful vigor for a certain amount of time and no longer. The rest of the organism's energy can then go toward maximizing fertility – which is the main goal of the exercise.
Kirkwood calls his model the disposable soma theory and likens it to industry's practice of investing little in the durability of goods that will be used for only a limited time. In an organism's case it is the somatic cells – the nonreproductive cells making up the bulk of the body – that are eventually expendable. In contrast, germ-line cells, occurring in tissues that give rise to eggs and sperm, must retain the ability to repair themselves perfectly, otherwise the species would die out. Because genes in germ-line cells account for only a tiny fraction (typically less than 1 percent) of total body genes, the cost of maintaining high-precision error-correcting processes in the ovaries and testes is tolerably low.
At some stage in the dim past, then, it seems that evolution stumbled upon a novel solution to the problem of reproduction. It put immortal, "selfish" genes in disposable shells. This was the successful formula that led to all of the more complex life-forms on Earth – including man.
But with the evolution of ourselves there arose a special and unique complication. The perishable machine built by human genes contains the most highly developed brain we know. This brain, like the rest of the body, has a finite lifespan. Yet it is also the vehicle for our indomitable sense of self.
Man's brain was the first on this planet to be able to project its thoughts into the future, to be able to predict events based upon experience. So, inevitably, it was also the first brain to be able to foresee its own end. That was the tragedy in the tale of the fall from Eden: with the birth of the ego, death entered our consciousness.
Death is not nearly so old as life, but self-consciousness and the fear of death are much younger still. Other animals appear not to have these in any developed form at all, and even man, some circumstantial evidence suggests, may not always have enjoyed full self-awareness as we know it today.
From prehistoric remains it is hard, and perhaps unrealistic, to try to reconstruct the mental and spiritual worlds of our long-dead ancestors. All our theories are bound to be parochial, tainted as they are by present-day attitudes and beliefs. Fortunately, though, we have more than just fossil evidence to go by. There are folk still alive today who almost certainly preserve, in both their memories and traditions, the essence of Neolithic man.
For at least 40,000 years the Aborigines have lived in Australia and for almost all that time they have practiced the hunter-gatherer lifestyle once common to all men. Although during the last century they became permanently settled, their surviving languages and customs serve as an extraordinary window on the remote past.
That window is not always very clear. We forget sometimes that there are ways of thinking, ways of interpreting the world, that are totally alien to our own, and the truth is that the intricacies of Aboriginal traditions are often hard for Westerners to follow. But a striking feature of native Australians that does come through is their attitude toward self. Aborigines – certainly pre-European Aborigines – were far less concerned with thoughts about their personal identities than about their relationship with the land and with other living things around them. Individuals saw themselves as part of a vast, unchanging, interconnected system. They considered themselves not simply in terms of bloodlines or families, but as deeply and inseparably connected with the wider context of the social group and, beyond that, the whole mythical structure of life. All the evidence suggests that Aboriginal consciousness was, and to some extent still is, collective and communal.
Time also seems to be perceived quite differently in the Aboriginal world. To the Aborigine, time appears cyclical rather than linear, because life itself is cyclical. The grass sprouts in the spring, grows green in the summer, withers in the autumn, dies in the winter, but always returns again the following year. This is the invariably observed pattern, the wheel of nature turning round and round. And because, to the Aborigine, Man himself is an integral part of nature, he too must participate in the recycling process. In the deepest sense, the Aborigine has no fear of death because, as far as he or she is concerned, nothing ever dies.
Death, or at least our perception of it, is something relatively new. We think of death as being tragic, terrifying, even repugnant. But it has none of those qualities if you see it every day in a natural context, if you hunt and collect your own food, if you are continually in touch with the cycle of the seasons. "Primitive" men and women considered themselves inseparable elements – cells as it were – of a social organism: a Gaean entity whose life continued out of an indefinite past and into an indefinite future. What we know today as the soul was, judging by the prevailing beliefs of primitive people now, originally thought of as a larger life embodied in the successive members of the group. At death, this personalized life simply returned like a river to the collective tribal sea.
For virtually all of human history, a span of between two million and three million years, it has been this way. The rights of the individual have been secondary to the rights of the group. The consciousness of the individual has been subordinate to the unitary, indestructible consciousness of the tribe.
Then, at some point less than 10,000 years ago, there came a change. Man began to build settlements as he learned to cultivate crops and domesticate animals. He erected walls and cities to protect himself and his property. And at the same time it seems that the beam down which man looked out on the world became more and more tightly focused. Nature became detached, something "out there." The tribal links were weakened and, we may conjecture, consciousness increasingly withdrew into the individual. To a greater extent perhaps than ever before, people became preoccupied by their personal sense of self and with a new and terrible image: the specter of death.
How sudden and recent was this subtle shift in the location of consciousness? In a highly controversial thesis, first published in 1977, Princeton psychologist Julian Jaynes proposed that self-awareness was still only partially developed as late as the second millennium B.C. Jaynes based his claim on analysis of several important ancient texts, including Homer's Iliad, written about 3,000 years ago. In these he found no reference to minds, thoughts, feelings – or to self. He concluded, therefore, that the people of this time did not recognize their thoughts and actions as their own but believed instead that they emanated from the gods. As an example, he cited an episode from the Iliad concerning the Greek hero Achilles. One god makes Achilles promise not to go into battle against the Trojans, another urges him on, and yet another screams through Achilles' throat at the enemies. Homer portrays mighty Achilles as if he were a puppet dancing to the thoughts and wills of higher minds.
It might well be argued, of course, that Homer intended his story to be interpreted this way: as a conflict fought out not just between men but also between the Olympian gods acting through men. After all, there is nothing new in the idea that men sometimes act of their own free will and at other times are driven to certain actions by circumstances beyond their control. While Jaynes's thesis is intriguing, it is far from convincing. He puts the birth of self-awareness at some point after 1000 B.C., but in all likelihood it happened very much earlier.
The emergence of a sense of self was surely a gradual process influenced by both biological and cultural factors. It takes a brain of a certain size and complexity – though not necessarily a human brain – to subtend a sophisticated sense of self. But the blossoming of that sense of self can take place only in the right environment – an environment in which your fellows relate to you (and you to them) as if you were a free-thinking individual in your own right.
This suggests that the evolution of self-awareness and that of language were strongly intertwined. Only through language are we able to break the world down into parts, to name objects and their interrelationships. Eventually, as part of this labeling, parsing process, we must have come to see ourselves as separate beings with separate, distinct minds.
The dawning of self-awareness in a form we would now recognize probably came while there were still quite primitive spoken tongues. Yet with speech the emphasis is on interaction with others, on the communal sharing of information. The only time that speaking throws the self into sharp relief (internally) is when we talk alone. Self-consciousness seems to go hand-in-hand with the ability to hold a one-man conversation. So, conceivably, the later stages in the growth of self-consciousness were encouraged by instances when some of our Stone Age forebears turned around to find that the person they had been talking to was no longer there.
Writing, too, when at last it appeared, may have played a part in the final honing of an awareness of self. Whereas spoken language is generally communal, written language is invariably personal. The only interpreter of a given sequence of written symbols is the mind that scans it, so that reading is essentially a self-conversation between the individual and the text. For the writer, the sense of self is further emphasized because the mind that is writing has to build consciously an external representation of its own internal workings.
Self-consciousness surely evolved, for the most part, very gradually. There were no instantaneous breakthroughs, no one who woke up and for the first time in the history of the world thought of himself as "I." We cannot even quantify or make comparisons of consciousness as we can, for instance, the cranial capacity of modern man and his ancestors. So, inevitably, all our proposals about how and when the various stages of awareness arose are purely conjectural.
Yet that does not make the guessing game any less intriguing. We know that self-consciousness has grown: a mouse is manifestly more self-aware than a minnow; we are more self-aware than a monkey. So it is pertinent to ask whether there were indeed periods in prehistory and history when man's view of the world and of himself evolved faster than usual. A tenuous clue, perhaps, comes from the Sumerian folk legend known as the Epic of Gilgamesh, which in its oldest surviving form comes to us on twelve five-thousand-year-old clay tablets from the library of Ashurnasirpal at Ninevah. In this ancient tale we read that the death of Gilgamesh's companion, Enkidu, has stunned the hero. Gilgamesh laments: "Enkidu, I weep for you like a wailing woman. You were the axe by my side, the sword in my belt, the shield before me. I also will die and worms will eat my flesh. I now fear death and have lost all my courage."
It is the man, the self-aware ego, that is lamenting here. And we are left with the impression that his grief reflects a newly acquired and painful sense of personal isolation in the people in general of this time. The myth goes on to tell how Gilgamesh, by performing certain rituals, wins permission from the gods of the underworld for the spirit of Enkidu to return to tell him about the state of the dead. Enkidu speaks of a House of Darkness in which the inhabitants are compelled to stay forever, feeding on dust and clay and wearing wings like birds for garments. And, again, we are struck by the acute loss of community, a loss tempered by a new hope – that each man and woman has an immortal spirit of his and her own. Just as the consciousness of the tribe has fragmented into separate selves within the city-state, so apparently the collective, tribal soul has been perceived as broken apart into the souls of individuals.
Opinions may differ. We may never know when and over what length of time man, unlike other animals, became fully ego-conscious. But of this we can be certain: when self-awareness did finally arrive it inevitably led to the quest for the survival of self after death.
Related books by David Darling (click on a cover to begin reading):
