Janus (27 page)

 

But another wasp,
Eumenes amedei
, goes still one better. The somewhat
gruesome description which follows is borrowed from
Darwin Retried
by Norman Macbeth: *

 

The egg is not laid upon or among the caterpillars, as in many allied
species. These caterpillars are only partially paralysed, and can
still move their claws and champ their jaws. Should one of them feel
the nibblings of the tiny grub, it might writhe about and injure the
grub. Both the egg and the grub must be protected, and to this end the
egg is suspended by a tiny thread of silk fastened to the roof. The
caterpillars may wriggle and writhe, but they cannot come near it.
When the grub emerges from the egg, it devours its eggshell, then
spins for itself a tiny silken ribbon-sheath in which it is enfolded
tail-uppermost and with head hanging down. In this retreat it is
suspended above the pile of living food. It can lower itself far
enough to nibble at the caterpillars. If they stir too violently
it can withdraw into its silken sheath, wait until the commotion
has subsided, then descend again to its meal. As the grub grows
in size and strength, it becomes bolder; the silken retreat is no
longer required; it can venture down and live at its ease among the
remains of its food. [31]
* This brilliant treatise by a Harvard lawyer highlights the
shortcomings and inconsistencies of the neo-Darwinian theory. Sir
Karl Popper called it a 'most meritorious and really important
contribution to the debate'.

 

At this point, I think, the mantra loses its hypnotic power even over
pious neo-Darwinists. As Tinbergen said: 'A genetics of behaviour still
has to be developed.' But the synthetic theory is unable to provide the
tools for it.

 

 

 

5

 

 

How could a doctrine which in effect begged all the basic questions gain
general acceptance among biologists and be considered as gospel truth by
the public? (The same question might be asked about behaviourism.) Part
of the answer is again found in von Bertalanffy:

 

I think the fact that a theory so vague, so insufficiently verifiable
and so far from the criteria otherwise applied in 'hard 'science, has
become a dogma, can only be explained on sociological grounds. Society
and science have been so steeped in the ideas of mechanism,
utilitarianism and the economic concept of free competition, that
instead of God Selection was enthroned as ultimate reality. [32]

 

This is no doubt part of the answer, but other factors also enter into it.
First, the theory contained a basic truth: the fossil record testified that
evolution was a fact, that Darwin was right and Bishop Wilberforce was wrong,
so Darwinism became something of a credo for all enlightened, progressive
people, while the details of the theory could be left to the experts.

 

 

The experts, however, including Darwin himself, soon ran into trouble.
There is a little-known episode in the early history of Darwinism which
is pertinent to our theme.* In 1867, eight years after the publication
of
The Origin of Species
, a professor of engineering at Edinburgh
University, Fleeming Jenkin, published an article which amounted to
a complete refutation of Darwin's theory.
^[33]
Jenkin demonstrated,
by an astonishingly simple logical deduction, that
no new species
could ever arise from chance variations
by the mechanisms of heredity
accepted at the time. For the theory of heredity, in Darwin's day, was
based on the assumption that the native endowment of the newborn was an
alloy or 'blend' of the characteristics of the parents, to which blend
each parent contributed approximately one half. Darwin's own cousin,
Francis Galton, gave a mathematical formulation to this 'law of ancestral
inheritance', as it was called. Assuming now that an individual endowed
with a useful chance variation (later to be called a random mutation)
cropped up within the species, and mated with a normal partner (i.e.,
with one of the vast majority of the population), then their offspring
would inherit only 50 per cent of the useful new characteristic, the
grandchildren only 25 per cent, the great-grandchildren 12.5 per cent,
and so on, until the hopeful novelty vanished like a drop in the ocean,
long before natural selection had a chance to make it spread.

 

* The following is a condensed version of the account of this episode
in The Case of the Midwife Toad, pp. 52 f.

 

It is remarkable, as Sir Alister Hardy wrote
^[34]
, that 'the
great brains of the Victorian era' did not notice the basic logical
fallacy which Jenkin pointed out. Darwin himself was so shaken that he
inserted a whole new chapter in the sixth edition of
The Origin
,
in which he resuscitated the Lamarckian theory of evolution through the
inheritance of acquired characteristics which earlier he had described
as 'a load of rubbish', and which is still anathema to Darwinists. As
his letters to Wallace indicate, he saw no other way out.* But Darwin's
followers ignored the master's relapse into the Lamarckian heresy (which,
anyway, did not provide the required answers), and during the last
decades of the nineteenth century Darwinism had run into a dead end --
although the public was unaware of it. The leading English Darwinist
at the time, William Bateson, wrote in retrospect: 'In the study of
evolution progress had well-nigh stopped. The more vigorous, perhaps
the more prudent, had left this field of science.'
^[36]

 

* His son, Francis Darwin, later commented: 'It is not a little
remarkable that the criticisms, which my father, as I believe, felt
to be the most valuable ever made on his views, should have come,
not from a professed naturalist but from a Professor of Engineering,
Mr Fleeming Jenkin.' [35]
Yet the sixth edition does not even mention his name.

 

In the year 1900, however, by an unexpected and dramatic turn of events,
the crisis was resolved -- or so it seemed at the time; the clouds vanished,
and Darwinisin became transformed into neo-Darwinism.

 

 

This crucial event was the rediscovery of a paper called 'Experiments in
Plant Hybridisation' by the Augustine monk Gregor Mendel, published
in 1865, in the
Proceedings of the Natural History Society of Brünn
(now Brno) in Moravia. Thirty-five years later, long after Mendel's
death, this paper was unearthed almost simultaneously and independently,
by three biologists in three different countries (Tschermak in Vienna,
de Vries in Leyden, Correns in Berlin). Each had been searching the
literature for some clue to indicate the way out of the cul-de-sac,
and each saw immediately the significance of Mendel's hybrid garden
peas -- which, like Newton's apple, were to become an integral part of
science-lore. Mendel's experiments showed that the 'units of heredity'
-- later to be called genes -- which determined the colour, size, and
other features of his plants, did not 'blend' and thus become diluted;
they were rather like hard, stable marbles which combined into a variety
of mosaic patterns, but preserved their identity and were transmitted
unchanged and intact to subsequent generations -- even though the effect
of 'recessive' genes was masked if they were paired with 'dominant' ones.

 

 

Here, at long last, was the answer to Jenkin's crucial objection. For it
could now be assumed that whenever a chance mutation occurred it would not
be whittled away through blendings, but would be preserved in successive
generations and thus give 'natural selection' a chance to pick and choose.

 

 

Now everything was falling into place. Every single factor determining
a hereditary trait was contained in a Mendelian gene, and every gene had
its allotted place in the chromosomes in the cell-nucleus, like beads
on a string. Evolution no longer had any secrets -- or so it seemed.
Bateson, instantly cured of his despair when he read Mendel's paper in
a railway carriage, gave his youngest son the name Gregory, in honour
of the Bohemian monk. 'Only those', he wrote twenty years later, 'who
remember the utter darkness before the Mendelian dawn, can appreciate
what happened.' [36]

 

 

The details of Mendelism do not concern us here, only its impact on the
theory of evolution. It turned out to be decisive.

 

 

Bateson was the first to show that Mendel's laws of inheritance applied
to plant and animal alike. He experimented on poultry; but the favourite
experimental subject of the new science of genetics was the small
fruit-fly
Drosophila melanogaster
, which propagates very fast
and has only four pairs of chromosomes. This made it possible to apply
statistical methods to the study of hereditary variations among large
populations of the fly caused by spontaneous or artificially induced
mutations (by irradiation, heat, etc.). In its own limited field, the
science of genetics was immensely successful, and still is. But it took
a long time for the more thoughtful among its practitioners to realize
that their labours, while providing new insights into the mechanisms
of minor hereditary
variations
, had little or no relevance to
the basic problem of
evolution
: the origin and why and how of
the major steps up the evolutionary ladder, the emergence of higher
life-forms and new life-styles. In the words of Pierre Grassé
who, let us remember, held the chair of evolution for thirty years at
the Sorbonne (italics in the original):

 

Variation is one thing, evolution quite another: this cannot
be emphasised strongly enough . . . [37]
Let us repeat it once more: mutations do not provide an explanation
for the nature or temporal order of the phenomena of evolution; they
do not create evolutionary novelties; they cannot account for the
precise fitting together of the parts of an organ, and the mutual
co-ordination of organs . . . [38]
Mutations provide change, but not progress . . . [39]
The repertory of mutations, or mutation-spectrum of a species
has nothing to do with evolution. The 'Jordanons' (equivalents of
mutations) of the whitlow grass (Erophila verna); of the
wild pansy (Viola tricolor); of the Plantains (Plantago); of
the candytuft (Iberis), which add up to a rich and well-catalogued
assortment, are the irrefutable proof of it. When all is said,
Erophila verna, Viola tricolor, etc., despite their
numerous mutations, do not evolve. This is a fact.
The various races of dogs, and of all the other domesticated animals,
represent merely the mutation spectrum of the species, manipulated
by artificial selection. The same applies to garden plants. Nothing
in all this amounts to an evolution. [40]

 

Nor, we may add, do Mendel's garden peas or the geneticist's fruit flies
have any real bearing on 'evolution by natural selection'. Mendel's
observations referred to such single traits as yellow seeds or green
seeds, purple flowers or white flowers, etc., which were dependent on
a single gene and were 'trivial' in the sense that they did not have
any evolutionary significance. Similarly, all the mutations observed or
induced in more than half a century of experimentation with
Drosophila
were either deleterious or trivial -- variations in the pattern of
bristles on the fly's body, in the colour of the eyes, etc. Such isolated
features which do not interact or interfere with the functioning of the
organism as a whole, can indeed be safely left to the roulette wheel. In
fact none of the mutations observed in millions of
Drosophila
have
produced offspring showing any evolutionary advantage.

 

 

Once more the Darwinian theory, in spite of the invigorating injection
of Mendelism, had come to a dead end. Bateson, who had been the first
in England to greet the 'Mendelian dawn', was also among the first to
express his disillusionment. Two years before his death in 1926, he
told his son Gregory that it was a mistake to have committed his life to
Mendelism, that this was a blind alley which would not throw any light
on the differentiation of species, nor on evolution in general. [41]

 

 

Even earlier he wrote in
Problems of Genetics
:

 

The many converging lines of evidence point so clearly to the central
fact of the origin of the forms of life by an evolutionary process
that we are compelled to accept this deduction, but as to almost all
the essential features . . . we have to confess an ignorance nearly
total. The transformation of masses of population by imperceptible
steps guided by selection is, as most of us now see, so inapplicable
to the facts, whether of variation or of specificity, that we can only
marvel both at the want of penetration displayed by the advocates
of such a proposition, and at the forensic skill by which it was
made to appear acceptable even for a time. [42]

 

Bateson coined the term 'genetics' and occupied the first university
chair devoted to the new field in Cambridge. Wilhelm Johannsen, the
Danish pioneer of neo-Darwinism, coined the term 'gene'. By 1923 he, too,
realized that all the experimental evidence spoke against the theory:
'The Problem of Species, Evolution, does not seem to be approached
seriously through Mendelism nor through the related modern experiences
in mutations.' [43]

 

 

Yet the upholders of the theory, steeped in the mechanistic tradition,
were apparently unable to see that random mutations of single factors
-- 'atoms' of heredity -- were irrelevant to the central problem of
evolutionary progress, which requires simultaneous, coordinated changes
of all the relevant components in the structure and function of the
organic holarchy. The geneticists' obsession with the bristles of the
fruit-fly, and the behaviourists' obsession with the lever-pressing
of the rat, show a more than superficial analogy: both derive from a
reductionist philosophy which regards the living creature as a collection
of elementary bits of heredity (Mendelian genes) or bits of behaviour
(conditioned reflexes or operant responses).