The Ghost in the Machine (11 page)
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 mitochondria 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 stabilisedThe hypothesis is in keeping with all we know about that ubiquitous
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]
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 cells 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
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