Biology of the soul.

In 1972, the eminent theologian John Hick published a treatise entitled "Biology and the Soul," which he had earlier delivered as the Eddington Memorial Lecture at Cambridge University. As a biologist interested in issues at the interface between science and religion, I thought that now, at last, I would learn what the biological basis of the soul might really be. Hick's paper summarized in an informed way the mounting evidence that a lot of what we are (including much of our behavior) is dictated by the genes we randomly inherit from our parents. Yet if that is all there is to it, what is left for a divinely infused soul to be responsible for?

Hick didn't consider the possibility that there may be no soul at all. He shed no light on when or how during prenatal development ensoulment supposedly takes place. He quite unaccountably ignored the soul's phylogenetic history during human evolution. He was remiss not only in failing to connect the supernatural soul with the natural world of biology but in neglecting even to identify where such connections might logically be sought.

Disappointed, I went back and reread the title. It said, "Biology and the Soul," not "Biology of the Soul." How, I wondered, could such a recognized scholar have ignored ad, dressing this obviously crucial relationship? Such is the state of the theological mind: it tends automatically to compartmentalize issues to avoid asking the hard questions. The present account is intended to redress some of John Hick's sins of omission.

Few tenets of religion strike so close to home as does the concept of soul. The soul is not off in some never-never land outside the universe, at least not until it takes up residence in the kingdom of heaven; it is right here inside each one of us, where we can keep an eye on it. If the soul is not identical to our mind or consciousness, it is very close to it. Its proximity renders it more amenable to verification than other theological concepts, as the anecdotes below testify.

Following the discovery of animal regeneration by Spallanzani in 1768, it became fashionable among the intellectual elite of Europe to chop off the heads of snails to observe their subsequent regrowth. Ever the philosopher, Voltaire speculated on the theological ramifications if human beings were someday to be able to replace their heads (a change which might not always be for the worse, he implied). If the pineal gland were in fact the seat of the soul, as Voltaire suggested, would a replacement endowed with a new soul also be regenerated?

When Admiral Lord Horatio Nelson lost his arm in the battle of Teneriffe in 1797, he later experienced phantom-limb sensations. If he could still feel his arm after it was gone, he reasoned, then perhaps his soul could survive the eventual demise of his body.

And there is the apocryphal story (from before the laws about informed consent) of weighing a terminally ill patient's body at the moment of death and recording a 14-ounce decrease in weight--the implication being that the soul is not so insubstantial after all!

These crude attempts to understand the concept of soul bear witness to our insatiable curiosity about the unexplained. They also betray a deep-seated skepticism about the super, natural, as if it could be proven or disproven by rational argument or empirical experiment.

Before embarking upon further experiments on this elusive entity, perhaps it would be prudent to give some thought to the very nature of that which we would investigate. The natural history of the soul--or the concept thereof--leads to some provocative ideas, especially where the scientific and the ecclesiastic, the real and unreal. supposedly intersect. Proponents of the existence of an immortal soul bear the burden of proof as to its provenance and prospects, its relationship to human ontogeny and phylogeny, and how it may be bound up with other difficult-to-understand concepts such as consciousness and free will.

Nonsensical Essences

Belief in a soul is a form of animism. There is a long history of endowing both animate and inanimate objects with spirits appropriate to their kind. Such dualism underlies the general concept of the supernatural: the notion that there is more than one world. The real world of matter and energy is supposedly paralleled by a world of immaterial essences, the natures of which cannot be known but which intuitively must be there. The supernatural--or as I prefer to call it, the extranatural--can neither be proved nor disproved owing to its ineffable character. Indeed, there could be as many extranatural worlds as there are intellects to conceive them, and others no one ever thought of. Their prevalence suggests that they must serve some deep-seated purpose in the human psyche. Perhaps it is our innate fascination with the unknown that renders their mystique so appealing. Everyone loves a mystery, so by ascribing the riddle of the universe to some esoteric source we are in no danger of solving the problem and thereby depriving ourselves of its fascination.

Not unrelated to animism is the notion of vitalism. Based on the belief that living things are fundamentally different from nonliving ones, vitalism was supposed to explain the spark of life (if only by assigning a name to it). We now know that there is no essential difference between living things and the non, living materials to which they can be reduced. The animate world is simply a matter of organization and negative entropy. Yet mystery still surrounds life--especially when the spark goes out.

Soul is a subset of vitalism. It is said to be immortal only in the human species, although other animals (but not plants, I think) are allowed to possess mortal souls. Heaven (or hell), it would seem, is the exclusive province of human souls. The basic rationale for having invented souls was probably to provide conveyance into the hereafter, or into another organism in the case of reincarnation. The soul presumably lived on after death the way it did while we were asleep--not an unreasonable assumption in pre-scientific times. Every, one worries about what happens to them after they die (the most important event in any, one's life), so the idea of an immortal soul departing the dying body for a better world found wide appeal. It is interesting that few people seem to be concerned about where our souls came from in the first place. Explaining one mystery in terms of another, the usual answer is from God, who purportedly infuses one into each human egg as it is fertilized, or into each fetus at birth, or somewhere in between, depending upon one's religious denomination. There is probably an infinite supply of souls, judging from the exponential rate of human population growth.

The Ontogeny of Identity

The ontogeny of the soul--or the history of its inception, development, and disappearance in each individual--involves a lot of guesswork. Not surprisingly, it closely parallels the self. Whatever it may be called, it is subjectively the most important part of our identity, that which each of us protects at all costs and without which we are nothing but flesh and bones.

Biological identity comes in two forms. One has a molecular basis, being responsible for the genetic uniqueness of each individual organism. The other is psychological, the memory, dependent awareness of self. It is one of the hallmarks of life that no two animals or plants are exactly alike, in contrast to the inanimate world in which each atom, molecule, or crystal is indistinguishable from every other of its kind. The uniqueness of individual life forms, as expressed antigenically and immunologically, for example, is attributable to the fact that their complexity exceeds their numbers. Even viruses, the simplest of all forms of life, are nevertheless enormously complex and mutable and therefore unique. But this kind of identity is not what inspired the concept of soul.

Even identical twins, though capable of exchanging tissues or organs with impunity, are nevertheless separate entities. Despite their uncanny similarities, they each possess a separate self or soul, if you will. It is this form of biological identity upon which the notion of soul depends. Closely related to self-awareness, the existence of a soul has even been extrapolated to include those with potential self-awareness, as in the case of prenatal life.

Fertilization is the earliest conceivable (pun intended) time for the divine infusion of a soul. Not until it becomes a zygote does the egg possess the genetic wherewithal to begin its development. Although it is a long way from acquiring awareness of its perceived surroundings (not to mention becoming cognizant of its awareness), the acknowledged possibility of its so doing justifies recognition of the fertilized egg as a human being. This approach also avoids the con, fusion of pinpointing ensoulment at later stages of embryonic or fetal development, all of which--with the exception of implantation and parturition--are gradual processes not lending themselves to unambiguous identification. Little wonder that opponents of abortion draw the line at fertilization.

Although anti-abortionists are genuinely concerned about the destruction of defenseless life in the womb, they are equally opposed to the loss of human souls. This explains why the abortion controversy is not so much a medical debate as it is a religious dispute. A procedure that should be decided on moral grounds has instead become a religious issue. Whether the Bible approves or disapproves of abortion, it is silent on the question of when in the course of gestation the soul may have been acquired. The existence of sperm and eggs were unknown in biblical times, not to be discovered until after the invention of the microscope. Therefore, the current insistence that the soul takes up residence at fertilization was an arbitrary decision based on science, not religion. It was also a sexist decision, implying that the male sperm is responsible for bringing the soul into the female ovum, for surely it could be no coincidence that the two events took place at exactly the same moment.

As every biologist knows, fertilization is not necessarily essential to the initiation of development. Although there are apparently no known exceptions in the human species, parthenogenesis (or virgin birth) is not an uncommon phenomenon in other animals, even in birds and reptiles. There, fore, it is at least hypothetically possible in placental mammals, including Homo sapiens. One wonders how or when the soul would be acquired without the benefit of fertilization if parthenogenesis were proven to occur, however rarely, in our own species.

Thus, fertilization may be important, but it is not the beginning of life. It is a mechanism of genetic recombination ensuring diversity in a population. And it somehow also triggers the onset of embryonic development (although a pin prick may suffice in lower forms). But fertilization is not how life began. Ever since 1893, when August Weismann formulated his theory of the continuity of all life through the germ plasm, it has been universally recognized that the beginning of life dates back to the very origin of life on earth. It follows that all organisms are related, as the prevalence of their similiarities over their differences testifies. The germ line transcends generations, the individuals of which grow old and die but live on in the biological sense through their progeny. If one subscribes to the idea of souls, then these are but transient things intermittently residing in individual members of a single species in the vast continuum of life. They are a latecomer in the course of organic evolution, not appearing until there evolved sentient creatures aware of their own mortality and able to concoct a scheme of how to live forever.

A Soul Gene?

It is incumbent on the theologian proposing the existence of souls to explain how they may have evolved. For more fundamentalist types who do not believe in evolution, this is not a problem. But for the majority of clergy who accept scientific discoveries, including evolution, there are serious inconsistencies to be explained. Few people bother to think about these matters, but the inquiring mind cannot ignore the incompatibilities implicit in considering the phylogeny of the soul. Indeed, this is the main reason why religion and evolution cannot be reconciled, even by those religious liberals who would have us believe that evolution was itself part of the divine handiwork of the creator.

If all organisms possessed souls, it would be simple enough to propose that these disembodied spirits evolved hand in hand with the plants and animals in which they dwelt. But religions tripped themselves up when they reserved their souls for human beings alone. This dogma requires that there must be a sharp distinction between people and other primates. Yet evolution is a gradual process. Our distant ancestors developed from their distant ancestors, who came from still more distant precursors intermediate between them and more ape--like antecedents. Little by little, generation by generation, the backbone became more erect, the arms shortened, the body hair thinned, the thumb became more opposed to the fingers, vocalization blossomed into speech and language, and the brain enlarged. There was no specific point during this transition when a pair of ape parents begat a human baby. And even if they did, the entire human race would have had to descend from that one infant. Alternatively, ensoulment might have taken place throughout the entire population of incipient humans, young and old alike, at some particular moment in the dim past. On the other hand, perhaps soulness is a matter of degree, such that, as the future human species evolved, it just as gradually acquired increasing amounts of soul. Maybe subsequent evolution will continue this trend of increasing the amount or quality of souls in the millennia ahead. All of these speculations raise interesting questions about the nature of the soul--questions which really should be addressed by a responsible clergy.

In any case, if the biological differences between humans and beasts are genetic, then their so-called spiritual differences must also have a genetic basis. This implies that there ought to be a gene for soul in human DNA--a gene that arose by mutation at that landmark in primate evolution when the first human being made its appearance amongst a population of astonished apes. Yet even if the soul gene were dominant, it would still have taken many generations for it to have spread throughout the population. And this presupposes that it was such an advantageous adaptation that it would have been favored by natural selection. One wonders if possession of a soul might really have enhanced survival in the struggle for existence, thereby promoting greater reproduction by those with a soul over those without.

I can imagine some clergy attributing the selective advantage of the evolving soul to its relationship with morality. After all, morality is what separites humans from beasts, and it is what determines where one's immortal soul is to spend eternity. This line of reasoning might explain spiritual survival in the hereafter but not bodily survival in the heretofore.

Obviously, the unabashed speculations above are enough to make a self-respecting biologist blush. They would probably be considered blasphemous by certain clergy, for they go far beyond anything ever intended by church dogma. Either way, they are scientifically ridiculous because they attempt to explain the extranatural in material terms, and they are theologically nonsensical because such nebulous concepts as spirit or soul were never meant to be subjected to rational explanations in the first place. Therein lies the problem whenever extranatural worlds encounter the natural one. Something has to give because the two, by definition, are incompatible.

Let there be as many "other worlds" as peoples' creative imaginations can conjure, but let them intersect the material world of science at their peril. If one asks why these concepts persist, it is simply because people in general believe whatever they want to believe and their religious leaders do not feel it is dishonest (or immoral) to believe something without evidence. In fact, we are told again and again that faith is a virtue, especially when it is blind. Alas, articles of faith unsupported by evidence are by their very nature arbitrary.

The Selfish Soul

Realistically, what is commonly referred to as soul is felt to reside in our minds (although its more visceral attributes may lead some to position it in the heart). When we speak of spirit, we usually mean emotion, al feelings. Of all the dimensions of our mentality, emotions are the most mystical as well as the most important. Life would indeed be empty (and, dare I say, meaningless?) were it not for the kaleidoscope of feelings we experience in reaction to its ups and downs. Our emotions sweep over us, sui generis, often with no apparent cause. No wonder they are interpreted as evidence of spirits or of an extranatural soul.

Of no less importance, however, is our sense of self. It is the very basis of our personal identity, remaining unchanged from infancy to old age. If anything is equivalent to what theologians call soul, it is what psychologists call self-awareness. Human animals are remarkably endowed with the knowledge that they are conscious. We cannot be entirely certain whether or not lower animals, while well aware of their environment through sensory impressions, are also cognizant of their own awareness. Such a concept may be too abstract for their limited intellects, and this is undoubtedly the reason why the concept of soul has been restricted to human beings. Therefore, to understand soul we need to understand consciousness, and this is almost as slippery a subject'

A major part of consciousness is sensation and perception. Our minds are constantly bombarded with sensory inputs which are translated into the mental impressions we have of our environment. However convincing it may be to experience blueness, loudness, or softness--or to know the feelings of beauty, love, or panic--these are not what the real world out there is like. These are mental constructs, either pleasant or painful, which are in the eye (so to speak) of the beholder.

Philosophers have long debated whether or not there would be any mental activity without sensory impressions; for if the mind were in fact a tabula rasa, it would have nothing to think about or to be conscious of. But even in a hypothetical state of total sensory deprivation, there might still be one thing a mind might be aware of: namely, itself. If awareness of the environment depends upon the traditional five senses, awareness of the mind itself must involve the perceptions of the mind by the mind--a kind of cerebral proprioception, as it were. This "sixth sense," by which we are able to think about our thoughts, to be conscious of our consciousness, is contingent upon a certain amount of innate intelligence and may therefore be a property of the human mind alone. It is probably no coincidence that this sense of self has been interpreted by those possessing it as something that is not only unexplainable but also of divine origin, like the soul.

Psychologists and neuroscientists alike are admittedly stumped by the phenomenon of consciousness. This is because it is strictly subjective and therefore not amenable to objective investigation by the scientist. It is said to be without location in space, which renders it too elusive to pin down. Our thoughts and volitions have been referred to as "causal primaries," a euphemism for uncaused events which are per-force not subject to scientific exploration. That which is beyond the realm of scientific research is in danger of being assigned to the extranatural, as if this were better than admitting our ignorance. So it is that our consciousness has been anointed with divine qualities which serve more to obfuscate than to illuminate its true nature.

Proponents of the soul hypothesis would have us believe that consciousness transcends the existence of the brain in time and space. Its transcendental quality, adorned with ecclesiastical embellishments, equips the consciousness for eternal survival in paradise long after its material substrate is gone. Too often, even scientists who should know better subscribe to this hypothesis, though it is impossible to prove or disprove.

Yet consciousness is not so far beyond the bounds of science as some would have us believe. As an emergent quality of the brain, it should be reducible to cerebral physiology and, ultimately, to molecular reactions, electrical depolarizations, and synaptic transmissions. Yet reduction is a difficult concept for most philosophers to accept because it smacks a bit too much of determinism.

Most people, when asked what causes their thoughts, reply, "I do'." This is because most people would sooner give up belief in God than abandon their conviction of free will. It is too much even for the scientific ego to deny the freedom its volition, lest it relinquish control of its most valuable piece of equipment--that situated between the ears. If our volition, like our thoughts and our consciousness, is not determined even in the statistical randomness of quantum physics, then its purported freedom must derive from something extranatural, like the soul.

The above reasoning leads us down a blind alley, and all because some philosophers and scientists are reluctant to admit that consciousness might just be amenable to objective investigation. For example, consciousness does in fact exist in space. That space is in the brain, or parts thereof. In point of fact, studies of split-brain subjects produced by prefrontal lobotomy suggest that each hemisphere may have a separate consciousness. Such an interpretation is consistent with the phenomenon of twinning, whereby a single fertilized egg, if it separates early enough into two embryos, develops two minds (and souls?) from what was originally a single individual. Experimental embryologists have also succeeded in the reverse operation, in which two early mouse embryos can be merged into one and then allowed to develop into a single creature. What can be achieved in one mammalian species is hypothetically possible in another, including our own, suggesting that, if souls can be split, they can also be fused.

That consciousness resides in and depends upon the brain is supported by much evidence, not the least of which involves the effects of traumatic injuries. If you are knocked out by concussion, you lose consciousness. If you suffer a cerebral stroke, your consciousness may be deprived of some of its important dimensions. If you take certain drugs, you may be transported into an altered state of consciousness. If you are afflicted with Alzheimer's disease, you may eventually lose your memory, including the memory of who you are. What you do to the brain, you do to consciousness. What more convincing evidence do we require in order to conclude that consciousness is to the brain what contraction is to muscle or excretion is to the kidneys?

By positron-emission tomography (PET scanning), it is possible to visualize on a screen what is going on in the brain in terms of glucose localization, for example, and metabolic activity. Studies have shown that certain aspects of brain physiology change with shifting mental activities. Theoretically, such supposedly nebulous events as consciousness, thinking, and emoting are metabolic processes that consume energy. They are therefore not beyond the scope of scientific measurement. Just as our urges and appetites may be generated by hormones, so the very thoughts I am putting down on paper may well be the result of a long concatenation of prior thoughts all produced by shifting constellations of physiological activities in my brain. Subjectively, I have the feeling that they are my own ideas, but intellectually 1 know they come only from metabolic activity, self-organized but nevertheless subject to the rules of causality.

Those who are horrified at the idea of a deterministic brain will find it difficult to conceive how its various modalities can be without deeper meaning. The appreciation of beauty, the thrill of romantic love, the exaltation of discovery, the anguish of pain: can these be reduced to nothing more than stimulus, response reactions, enzymatic activities, electrical impulses, or the rush of endorphins? To explain the very basis of our mental being in mechanistic terms is like abolishing a beautiful emotion by stopping in full ecstasy to analyze it. It has been said that virtue, like ignorance, is diminished by becoming aware of it, and the same may be true of the illusion of innocence, which can be sustained only by denying ourselves the right to understand and explain it. Assuming that the noblest human endeavor is to seek the truth, even when the results are iconoclastic, then the delicate sensitivities of those who cling to more mystical interpretations of what goes on in our brains may be offended by the honest attempts of neuroscientists to explain away their most cherished delusions. But if the alternative is belief in a divine soul that by definition cannot be understood, then surely the human race must abandon hope of saving itself, not from perdition but from extinction. Theologian Hick and his ilk seem more interested in saving souls than in saving humanity, without which there would have been no souls in the first place.

Richard J. Goss is a former dean and professor emeritus of biology at Brown University in Providence (RI). As an embryologist, he has devoted his professional career to the study of regeneration.