The Ghost in the Machine (24 page)

 

* Cf. The Act of Creation, Book Two, Chapter Eight.

 

The exploratory drive has a direct bearing on the theory of evolution.
This was realised by at least two eminent biologists at the turn of the
century -- Baldwin and Lloyd Morgan -- but was promptly and conveniently
forgotten. In recent years, however, this so-called 'Baldwin effect'
was rediscovered, independently, by Hardy and Waddington. Let me explain
what is meant by an amusing example which Hardy gave at a meeting of the
Linnaean Society in 1956. A few years earlier, some clever blue-tits had
noticed that the bottles which the milkman left at the doorstep contained
a puzzling white liquid, and they discovered a way of getting at it by
removing the tops of the bottles with their beaks. The liquid proved to
be rather delicious. So the birds learned to deal with cardboard tops,
and soon also with metal tops. This new skill soon spread, apparently
by imitation, 'right through the tit population of Europe' [6]

 

 

Never again will our milk bottles be safe. However, Hardy continued,
if the bottles were living organisms -- a species of clams with an odd
cylindrical shell; and if the tits continued to feed on them, then after
a while only the 'bottles' with thicker caps would survive, and natural
selection would produce a species of 'thick-capped bottles' -- but also
perhaps a species of tits with 'more specialised, tin-opener-like beaks
for dealing with them'. [7]

 

 

The emergence of thick-capped 'bottle' creatures would illustrate
the
passive
, Darwinian type of evolution through the selective
pressure of predators in the environment. But the evolution of tits with
more efficient beaks is meant to illustrate a quite different type of
evolutionary process, based on the
initiative
of some enterprising
individuals in the species. These discover a new method of feeding, a
new skill which, spreading by imitation, becomes incorporated into the
species' ways of life. The lucky mutation (or re-combination of genes)
which produces beaks appropriate to the new skill comes only afterwards,
as a kind of genetic endorsement of the discovery. The initial act in the
process, the evolutionary pioneer work, so to speak, was done by the tit's
exploratory activities, its curiosity which led it to investigate the
environment -- and not merely submit to its pressures. We have seen that
the famous typewriter of the monkey is controlled by internal selection;
now the machine has been further programmed: the monkey merely has to
go on trying until he hits a certain pre-specified key.

 

 

The example of the tin-opener beak is of course imaginary, but the
conclusions are supported by many observations. Thus one of 'Darwin's
finches' on the Galapagos Isles, C. pallidus, pecks holes or crevices
into the tree bark, and 'having excavated, it picks up a cactus spine
or twig, one or two inches long, and holding it lengthwise in its beak,
pokes it up the crack, dropping the twig to seize the insect as it
emerges. . . . Sometimes the bird carries a spine or twig about with
it, poking it into cracks and crannies as it searches one tree after
another. This remarkable habit . . . is one of the few recorded uses of
tools in birds' (Hardy [8]).

 

 

According to the orthodox theory, we would have to believe that some
random mutation, by modifying the shape of the bird's beak (which,
however, is not very different from the beaks of other finches) caused it
to develop its ingenious way of hunting insects. And we would also have
to believe that it was the same
deus ex machina
which forced
the tit to open milk bottles. Let us rather agree with Hardy that 'the
emphasis in the present-day view must be false'; and that the main
causative factor of evolutionary progress is
not
the selective
pressure of the environment, but the initiative of the living organism,
'the restless, exploring and perceiving animal that discovers new ways
of living, new sources of food, just as the tits have discovered the
value of the milk bottles. . . . It is adaptations which are due to the
animal's behaviour, to its restless exploration of its surroundings, to
its initiative, that distinguish the main diverging lines of evolution;
it is these dynamic qualities which led to the different roles of life
that open up to a newly emerging group of animals in that phase of their
expansion technically known as adaptive radiation -- giving the lines
of runners, climbers, burrowets, swimmers, and conquerors of the air.' [9]

 

 

One might call this the 'progress by initiative', or do-it-yourself
theory of evolution. It does not do away with chance mutations, but
further narrows down the part played by them in the total picture to that
of a lucky hit at a pre-set target, which is sooner or later bound to
occur. Once it has occurred, the spontaneously acquired habit or skill
becomes hereditary, incorporated into the animal's native repertory:
it has no longer to be invented or learned, it has become an instinct,
endorsed by the gene-complex.* In fact, the range and importance of
random mutations has been so much whittled down by the various factors
mentioned in this and the previous chapter, that the whole Darwin-Lamarck
controversy loses much of its importance.

 

* In a series of experiments with Drosophila, Waddington has
demonstrated that such 'genetic assimilation' (as he called it)
of acquired characters becoming hereditary does indeed occur. This
does not necessarily mean, however, that Lamarck was right and
that the acquired feature (in this case a change in the fly's
wing-structure, produced by exposure of the pupae to heat) was the
direct cause of the mutation which made it hereditary after
a few generations, so that the wing-change occurred even without
heat-exposure. It could be that a few mutant flies were already
present in the stock, and were then selected for survival on a
Darwinian basis; it could also be that the appropriate mutation
arose by chance in the process.  Waddington leaves the question open
whether he had produced an experimental confirmation of Lamarck,
or an imitation of Lamarckian inheritance by means of a Darwinian
mechanism; he concludes that 'it would be unsafe to consider that
the occurrence of directed mutation related to the environment can
be ruled out of court a priori', and that 'it seems wisest
to keep an open mind on the subject'. [10]  That is a far cry from
the almost fanatical attitude of the neo-Darwinian citadel.

 

Waddington has gone even further by maintaining that if natural
selection works primarily in favour of plastic, adaptable behaviour,
then the process of canalisation during development will become so
flexible in itself that it no longer requires any particular gene
mutation to endorse the new feature, merely 'some random mutation
to take over the switching function of the original environmental
stimulus. The type of hereditary change envisaged by Baldwin is,
therefore, much more likely than he could have realised.' [11]

 

 

The point will perhaps become clearer if we draw a parallel between the
role of chance in evolution and in scientific discovery. Behaviourists
tend to ascribe any original idea to pure chance. But the history
of science teaches that most discoveries were made by several people
independently from each other, at more or less the same time;* and this
fact alone (apart from all other considerations) is sufficient to show
that when the time is ripe for a given type of invention or discovery,
the favourable chance event which sparks it off is bound to occur sooner
or later. 'Fortune fayours the prepared mind', wrote Pasteur, and we
may add: fortunate mutations favour the prepared animal.

 

* See The Act of Creation, pp. 109 ff.

 

A stupid and industrious scholar could indeed write a history of science
as a history of lucky hazards: Archimedes' overspilling bath-water,
Galileo's swinging chandelier, Newton's apple, James Watt's tea-kettle,
Harvey's fish-heart, Gutenberg's wine-press, Pasteur's spoilt culture,
Fleming's nose-drip -- and so on and so forth, whether apocryphal or
true does not matter. But he would have to be very stupid indeed not to
realise that if that particular chance event had not occurred, a hundred
others might have had the same triggering effect on the prepared mind
-- -or on some other contemporary mind working in the same direction;
and only a very perverse historian could fail to see that the primary
cause and directing force of scientific progress is the curiosity and
initiative of scientists, and not the random appearance of chandeliers,
apples, tea-kettles and nose-drips 'in all and every direction'.

 

 

Yet it is precisely this perverse view which determines the orthodox
interpretation not only of the evolution of new animal forms, but
also of new patterns of animal behaviour. The only explanation that
neo-Darwinian theory has to offer is that new forms of behaviour, too,
arise from chance mutations affecting the nervous system, preserved
by natural selection. If, apart from a few tentative studies, the
evolution of behaviour (as distinct from the evolution of physical
structures) is still an uncharted territory, the reason may perhaps be an
unconscious reluctance to put the already strained theoretical framework
of neo-Darwinian genetics to an additional test. To quote a very trivial
example: an individual song-bird or jackdaw or sparrow, on spotting a
predator, will give an alarm call, warning the whole flock. 'These alarm
calls', Tinbergen points out, 'are a clear example of an activity which
serves the group but endangers the individual.' [12] Are we really to
assume that the 'wiring diagram' in the sparrow's nervous system, which
releases the alarm call in response to a stimulus of predatory shape,
arose by random mutation and was perpetuated by natural selection in spite
of its negative survival value for the mutant? The same question could be
asked concerning the phylogenetic origin of the ritualised mock-fights
in a great variety of animals, including stags, iguanas, birds, dogs,
fish. Dogs, for instance, sprawl on their backs as a token of defeat and
surrender, exposing their vulnerable bellies and jugular veins to the
victor's fangs. One is inclined to call this a rather risky attitude;
and what is the
individual
survival value of
not
hitting
(or biting, goring) below the belt?

 

 

One could add a whole volume of examples of complex, purposeful animal
activities that defy any explanation by chance mutation and natural
selection; and the list would actually have to start with a single-celled
sea animal, a relative to the amoeba, which builds elaborate houses out of
the needle-like spiculae of sponges. From this simple protozoan, without
eyes or a nervous system, which is but a gelatinous mass of flowing
protoplasm, through the architectural skill of spiders and insects,
through bottle-raiding birds, tool-making chimpanzees and up to man,
we find the same lesson repeated -- a display of patterns of instinctive
and learned behaviour which cannot be explained by any twist of logic
as the result of random changes in bodily structure. To quote Dr. Ewer:
'Behaviour will tend to be always a jump ahead of structure and so
play a decisive role in the evolutionary process.' [13] In this light,
evolution no longer appears as a tale told by an idiot, but rather as
an epic recited by a stutterer -- at times haltingly and painfully,
then precipitating in bursts.

 

 

 

Once More Darwin and Lamarck

 

 

There remains a hard core of phenomena that seems to defy explanation by
any of the processes discussed so far, and to cry out for a Lamarckian
explanation in terms of the inheritance of acquired characters. There
is, for example, the hoary problem why the skin on the soles of our
feet is so much thicker than elsewhere. If the thickening occurred
after birth, as a result of stress, wear and tear, there would be no
problem. But the skin of the sole is already thickened in the embryo
which has never walked, bare-foot or otherwise. A similar, even more
striking phenomenon are the callosities on the Africa warthog's wrists
and forelegs, on which the animal leans while feeding; on the knees of
camels; and, oddest of all, the two bulbous thickenings on the ostrich's
undercarriage, one fore, one aft, on which that ungainly bird squats. All
these callosities make their appearance, as the skin on our feet does,
in the embryo. They are inherited characters. But is it conceivable that
these callosities should have evolved by chance mutations just exactly
where the animal needed them? Or must we assume that there is a causal,
Lamarckian connection between the animal's needs and the mutation which
provides them? Even Waddington, who does not completely rule out the
possibility of Lamarckian inheritance, prefers to invoke the Baldwin
effect and developmental canalisation though it is not easy to see how
they can satisfactorily explain phenomena of this kind.

 

 

But on the other hand, it is equally difficult to see how an acquired
callosity could conceivably produce changes in the gene-complex. Difficult,
but not entirely impossible. It is true that the germ cells are set apart
from other body cells in splendid isolation, but their isolation is not
absolute: they are affected by radiation, heat and certain chemicals.
It would indeed, as Waddington says, be 'unsafe to rule
a priori
out of court' the possibility that changes in the gene activities of
body cells could, under certain circumstances, also cause changes in the
gene activities of germ cells by means of hormones or enzymes. Herrick
[14] has also kept an open mind on the problem. Waddington has actually
produced a tentative model of directive mutation to indicate that at
the present stage of biochemistry such a process is conceivable. [15]