It may be useful to repeat at this point that the search for properties or laws which all these varied kinds of hierarchies have in common is more than a play on superficial analogies. It could rather be called an exercise in 'general systems theory' -- a relatively recent branch of science, whose aim is to construct theoretical models and 'logically homologous laws' (v. Bertalanffy) which are universally applicable to inorganic, biological and social systems of any kind.
Inanimate Systems
As we move downward in the hierarchy which constitutes the living organism, from organs to tissues, cells, organelles, macro- molecules, and so on, we nowhere strike rock bottom, find nowhere those ultimate constituents which the old mechanistic* approach to life led us to expect. The hierarchy is open-ended in the downward, as it is in the upward direction. The atom, itself, although its name is derived from the Greek for 'indivisible' has turned out to be a very complex, Janus-faced holon. Facing outward, it associates with other atoms as if it were a single unitary whole; and the regularity of the atomic weights of elements, closely approximating to integral numbers, seemed to confirm the belief in that indivisibility. But since we have learned to look inside it, we can observe the rule-governed interactions between nucleus and outer electron-shells, and of a variety of particles within the nucleus. The rules can be expressed in sets of mathematical equations which define each particular type of atom as a holon. But here again, the rules which govern the interactions of the sub-nuclear particles in the hierarchy are not the same rules which govern the chemical interactions between atoms as wholes. The subject is too technical to be pursued here; the interested reader will find a good summary in H. Simon's paper, which I have quoted before. [1]
* Throughout this book, the term 'mechanistic' is used in its general sense, and not in the technical sense of an alternative to 'vitalistic' theories in biology.
When we turn from the universe in miniature to the universe at large, we again find hierarchic order. Moons go round planets, planets round stars, stars round the centres of their galaxies, galaxies form clusters. Wherever we find orderly, stable systems in Nature, we find that they are hierarchically structured, for the simple reason that without such structuring of complex systems into subassemblies, there could be no order and stability -- except the order of a dead universe filled with a uniformly distributed gas. And even so, each discrete gas molecule would be a microscopic hierarchy. If this sounds by now like a tautology, all the better.*
* Often, however, we fail to recognise hierarchic structure, for example in a crystal, because it has a very shallow hierarchy consisting of only three levels (as far as our knowledge goes) -- molecules -- atoms -- sub-atomic particles; and also because the molecular level has an enormous 'span' of near-identical holons.
It would, of course, be grossly anthropomorphic to speak of 'self-assertive' and 'integrative' tendencies in inanimate nature, or of 'flexible strategies'. It is nevertheless true that in all stable dynamic systems, stability is maintained by the equilibration of opposite forces, one of which may be centrifugal or separative or inertial, representing the quasi-independent, holistic properties of the part, and the other a centripetal or attractive or cohesive force which keeps the part in its place in the larger whole, and holds it together. On different levels of the inorganic and organic hierarchies, the polarisation of 'particularistic' and 'holistic' forces takes different forms, but it is observable on every level. This is not the reflection of any metaphysical dualism, but rather of Newton's Third Law of Motion ('to every action there is an equal and opposite reaction') applied to hierarchic systems.
There is also a significant analogy in physics to the distinction between fixed rules and flexible strategies. The geometrical structure of a crystal is represented by fixed rules; but crystals growing in a saturated solution will reach the same final shape by different pathways, i.e., although their growth processes differ in detail; and even if artificially damaged in the process, the growing crystal may correct the blemish. In this and many other well-known phenomena we find the self-regulatory properties of biological holons foreshadowed on an elementary level.
The Organism and its Spares
As we ascend to the hierarchies of living matter, we find, even on the lowest level observable through the electron microscope, sub-cellular structures -- organelles -- of staggering complexity. And the most striking fact is that these minuscule parts of the cell function as self-governing wholes in their own right, each following its own statute-book of rules. One type of organelles look as quasi-independent agencies after the cell's growth; others after its energy supply, reproduction, communications, and so on. The ribosomes, for instance, which manufacture proteins, rival in complexity any chemical factory. The mitochondria are power plants which extract energy from food by a complicated chain of chemical reactions involving some fifty different steps; a single cell may have up to five thousand such power plants. Then there are the centrosomes, with their spindle apparatus, which organises the incredible choreography of the cell dividing into two; and the DNA spirals of heredity, coiled up in the inner sanctum of the chromosomes, working their even more potent magic.
I do not intend to wax lyrical about matters which can be found in any popular science book; I am trying to stress a point which they do not sufficiently emphasise, or tend to overlook altogether -- namely, that the organism is not a mosaic aggregate of elementary physico-chemical processes, but a hierarchy in which each member, from the sub-cellular level upward, is a closely integrated structure, equipped with self-regulatory devices, and enjoys an advanced form of self-government. The activity of an organelle, such as the mitochondrion, can be switched on and off; but once triggered into action it will follow its own course. No higher echelon in the hierarchy can interfere with the order of its operations, laid down by its own canon of rules. The organelle is a law unto itself, an autonomous holon with its characteristic pattern of structure and function, which it tends to assert, even if the cell around it is dying.
The same observations apply to the larger units in the organism. Cells, tissues, nerves, muscles, organs, all have their intrinsic rhythm and pattern, often manifested spontaneously without external stimulation. When the physiologist looks at any organ from 'above', from the apex of the hierarchy, he sees it as a dependent part. When he looks at it from 'below', from the level of its constituents, he sees a whole of remarkable self-sufficiency. The heart has its own 'pacemakers' -- in fact three pacemakers, capable of taking over from each other when the need arises. Other major organs have different types of co-ordinating centres and self-regulating devices. Their character as autonomous holons is most convincingly demonstrated by culture experiments and spare-part surgery. Since Carrell demonstrated in a famous experiment that a strip of tissue from the heart of a chicken embryo will go on beating indefinitely in vitro, we have learnt that whole organs -- kidneys, hearts, even brains -- are capable of continued functioning as quasi-independent wholes when isolated from the organism and supplied with the proper nutrients, or transplanted into another organism. At the time of writing, Russian and American experimenters have succeeded in keeping the brains of dogs and monkeys alive (judged by the brain's electrical activities) in apparatus outside the animal and in transplanting one dog's brain into another live animal's tissues. The Frankensteinian horror of these experiments need not be stressed -- and they are only a beginning.
Yet spare-part surgery has, of course, its beneficial uses, and from a theoretical point of view it is a striking confirmation of the hierarchic concept. It demonstrates, in a rather literal sense, the 'dissectibility' of the organism -- viewed in its bodily aspect -- into autonomous sub-assemblies which function as wholes in their own right. It also sheds added light on the evolutionary process -- on the principles which guided Bios in putting together the sub-assemblies of his watches.
The Integrative Powers of Life
Let us go back for a moment to the organelles which operate inside the cell. The mitocho
ndria transform food -- glucose, fat, proteins -- into the chemical substance adrenosin-triphosphate, ATP for short, which all animal cells utilise as fuel. It is the only type of fuel used throughout the animal kingdom to provide the necessary energy for muscle cells, nerve cells and so on; and there is only this one type of organelle throughout the animal kingdom which produces it. The mitochondria have been called 'the power plants of all life on earth'. Moreover, each mitochondrion carries not only its set of instructions how to make ATP, but also its own hereditary blueprint, which enables it to reproduce itself independently from the reproduction of the cell as a whole.
Until a few years ago, it was thought that the only carriers of heredity were the chromosomes in the nucleus of the cell. At present we know that the mitochondria, and also some other organelles located in the cytoplasm (the fluid surrounding the nucleus) are equipped with their own genetic apparatus, which enables them to reproduce independently. In view of this, it has been suggested that these organelles may have evolved independently from each other at the dawn of life on this planet, but at a later stage had entered into a kind of symbiosis.
This plausible hypothesis sounds like another illustration of the watchmakers' parable; we may regard the stepwise building up of complex hierarchies out of simpler holons as a basic manifestation of the integrative tendency of living matter. It seems indeed very likely that the single cell, once considered the atom of life, originated in the coming together of molecular structures which were the primitive forerunners of the organelles, and which had come into existence independently, each endowed with a different characteristic property of life -- such as self-replication, metabolism, motility. When they entered into symbiotic partnership, the emergent whole -- perhaps some ancestral form of amoeba -- proved to be an incomparably more stable, versatile and adaptable entity than a mere summation of the parts would imply. To quote Ruth Sager:
Life began, I would speculate, with the emergence of a stabilised tri-partite system: nucleic acids for replication, a photosynthetic or chemosynthetic system for energy conversion, and protein enzymes to catalyse the two processes. Such a tripartite system could have been the ancestor of chloroplasts and mitochondria and perhaps of the cell itself. In the course of evolution, these primitive systems might have coalesced into the larger framework of the cell. . . . [2]
The hypothesis is in keeping with all we know about that ubiquitous manifestation of the integrative tendency: symbiosis, the varied forms of parmership between organisms. It ranges from the mutually indispensable association of algae and fungi in lichens, to the less intimate but no less vital inter-dependence of animals, plants and bacteria in ecological communities ("biocoenosis"). Where different species are involved, the partnership may take the form of 'commensualism' -- barnacles travelling on the sides of the whale; or of 'mutualism', as between flowering plant and pollinating insects, or between ants and aphides -- a kind of insect 'cattle' which the ants protect and 'milk' for their secretions in return. Equally varied are the forms of co-operation within the same species, from colonial animals upward. The Portuguese man-of-war is a colony of polyps, each specialised for a particular function; but to decide whether its tentacles, floats and reproductive units are individual animals, or mere organs, is a matter of semantics; every polyp is a holon, combining the characteristics of independent wholes and dependent parts.
The same dilemma confronts us, on a higher turn of the spiral, in the insect societies of ants, bees, termites. Social insects are physically separate entities, but none can survive if separated from its group; their existence is completely controlled by the interests of the group as a whole; all members of the group are descendants from the same pair of parents, interchangeable and indistinguishable, not only to the human eye but also probably to the insects themselves, which are supposed to recognise members of their group by their smell, but not to discriminate between individuals. Moreover, many social insects exchange their secretions, which form some kind of chemical bond between them.
An individual is usually defined as an indivisible, self-contained unit, with a separate, independent existence of its own. But individuals in this absolute sense are nowhere found in Nature or society, just as we nowhere find absolute wholes. Instead of separateness and independence, there is co-operation and interdependence, running through the whole gamut, from physical symbiosis to the cohesive bonds of the swarm, hive, shoal, flock, herd, family, society. The picture becomes even more blurred when we consider the criterion of 'indivisibility'. The word 'individual' originally means just that; it is derived from the Latin in-dividuus -- as atom is derived from the Greek a-tomos. But on every level, indivisibility turns out to be a relative affair. Protozoa, sponges, hydra and flatworms can multiply by simple fission or budding: that is, by the breaking up of one individual into two or more, and so on, ad infinitum. As von Bertalanffy wrote: 'How can we call these creatures individuals when they are in fact "dividua," and their multiplication arises precisely from division? . . . Can we insist on calling a hydra or a turbelerian flatworm an individual, when these animals can be cut into as many pieces as we like, each capable of growing into a complete organism? . . . The notion of the individual is, biologically, only to be defined as a limiting concept.' [3]
A flatworm, cut into six slices, will actually regenerate a complete individual from each slice within a matter of weeks. If the wheel of rebirth transforms me into a flatworm meeting a similar fate, must I then assume that my immortal soul has split into six immortal solons? Christian theologians will find an easy way out of this dilemma by denying that animals have souls; but Hindus and Buddhists take a different view. And secular-minded philosophers, who do not talk about souls, but affirm the existence of a conscious ego, also refuse to draw a boundary line between creatures with and without consciousness. But if we assume that there exists a continuous scale of gradations, from the sentience of primitive creatures, through various degrees of consciousness, to full self-awareness, then the experimental biologist's challenge to the concept of individuality poses a genuine dilemma. The only solution seems to be (see Chapter XIV) to get away from the concept of the individual as a monolithic structure, and to replace it by the concept of the individual as an open hierarchy whose apex is forever receding, striving towards a state of complete integration which is never achieved.
The regeneration of a complete individual from a small fragment of a primitive animal is an impressive manifestation of the integrative powers of living matter. But there are even more striking examples. Nearly a generation ago, Wilson and Child showed that if the tissues of a living sponge -- or a hydra -- are crushed to pulp, passed through a free filter, and the pulp is then poured into water, the dissociated cells will soon begin to associate, to aggregate first into flat sheets, then round up into a sphere, differentiate progressively and end up 'as adult individuals with characteristic mouth, tentacles and so forth' (Dunbar [4]). More recently, P. Weiss and his associates have demonstrated that the developing organs in animal embryos are also capable, just like sponges, of re-forming, after having been pulped. Weiss and James cut out bits of tissue from eight to fourteen day old chick embryos, minced and filtered the tissues through nylon sheets, re-compacted them by centrifuging, and transplanted them to the membrane of another growing embryo. After nine days, the scrambled liver cells had started forming a liver, the kidney cells a kidney, the skin cells to form feathers. More than that: the experimenters were also able to produce normal embryonic kidneys by mincing, pooling and scrambling kidney tissues from several different embryos. The holistic properties of these tissues survived not only disintegration but also fusion. [5]
Fusion can even be induced between different species. Thus Spemann combined two half newt-embryos in their early, gastrular stage -- one a striped newt, the other a crested newt. The result was a well-formed animal, one side striped, the other crested. Even more spooky are recent experiments by Professor Harris at Oxford, who developed a technique for making human cell
s fuse with mouse cells. During mitosis, the cell-nuclei of man and mouse also fused, 'and the two sets of chromosomes were found to be growing and multiplying quite happily within the same nuclear membrane. . . . Such phenomena', one commentator wrote, 'will surely affect our concept of organism in some degree. . . . There are obviously sufficient possibilities along these lines to encourage or terrify everyone for some time to come' (Pollock [6]).
In the light of such experimental data, the homely concept of the individual vanishes in the mist. If the crushed and re-formed sponge possesses individuality, so does the embryonic kidney. From organelles to organs, from organisms living in symbiosis to societies with more complex forms of inter-dependence, we nowhere find completely self-contained wholes, only holons -- double-faced entities which display the characteristics both of independent units and of inter-dependent parts.
In the previous pages I have emphasised the phenomena of inter-dependence and partnership, the integrative potential of holons to behave as parts of a more complex whole. The other side of the story reveals, instead of co-operation, competition between the parts of the whole, reflecting the self-assertive tendency of holons on every level. Even plants, which are mostly green and not 'red in tooth and claw', compete for light, water and soil. Animal species compete with each other for ecological niches, predator and prey compete for survival, and within each species there is competition for territory, food, mates and dominance.