Darwin, Genes and Determinism
Steven Rose
Darwin is everywhere these days. We have Darwinian cosmology, Darwinian
medicine, Darwinian psychology, Darwinian psychiatry, Darwinian economics,
Darwinian computing, 'neural Darwinism,' even Darwinian models for cultural
change and the history of science. And we have genes for everything too.
Not just things we all know about, like eye colour, or diseases like sickle
cell anaemia or Huntingtons. there are, we are told, genes for
intelligence, sexual orientation, depression, criminal violence,
alcoholism, even 'compulsive shopping.' Whether we vote Labour or Tory, are
happily married or go in for mid-life divorce, are all claimed to be
somehow 'in our genes.' We are, the story goes, lumbering robots programmed
by our genes, which 'created us, body and mind' (the phrases are Richard
Dawkins'). Individual genes, 'naked replicators,' have become the basic
building blocks of life, and chickens merely the egg's way of making more
eggs. I doubt very much whether either Charles Darwin himself, or William
Bateson, who invented the term genetics, would recognise their ideas or
theories in the way the terms are being bandied about today.
Why this extraordinary upsurge? What we might call fundamentalist
Darwinism, in the hands of its popular exponents, has become a sort of all
purpose explanation for every aspect of our lives - indeed the philosopher
Daniel Dennett called it a 'universal acid' that eats through every area of
human thought. Perhaps it is because the deep fatalism which lies behind
the belief that our human nature is for good or ill somehow 'fixed,'
determined by our genes, suits a society in which we have lost the belief
that it is possible to create a more socially just world, and where that
other great 19th century explanatory principle, Marxism, has been almost
fatally damaged by the experience of the collapse of communism. If we seek
certainty in the world, the choices seem to lie between fundamentalist
religions like Christianity and Islam, and the seemingly scientific
fundamentalism of this version of Darwinism. Indeed there is something of
the religious in the way fundamentalist Darwinians cling to their
certainties. Invoking the name of Darwin to talk about changes in
cosmology, culture, or economic modelling, almost always misunderstands and
trivialises what remains one of the most important principles in biology.
How can I as a biologist possibly sound so hostile? It is because I want to
rescue both Darwin and the ideas about evolutionary and developmental
change, the nature of living processes, from the arms of the
fundamentalists who in my view abuse them.
That species have evolved is not a theory: it is a central fact of biology.
What is at issue is the mechanism of that evolution. Darwinian natural
selection is based on three simple and irrefutable propositions:
Like begets like, with minor variations
Some of these varieties are fitter - better able to survive - than others
All creatures produce more offspring than can survive to breed in their turn
It follows that:
the fitter varieties are thus more likely to breed than the less fit, and
hence to spread in successive generations.
And therefore that species evolve over time.
However, whilst this is a mechanism of evolution, it is, as Darwin himself
recognised, not the only one. It is good at explaining how species get
better at doing their species thing, but bad at explaining how new species
emerge. For this one needs other factors, like founder effects, and above
all sheer contingency - chance. Evolution cannot predict the future, and
the future may contain the asteroid which wiped out the dinosaurs, or the
catastrophes that overwhelmed the weird and wonderful creatures found
fossilised in the Burgess shale, which Steven Jay Gould writes about so
well in his book Wonderful Life. Fundamentalist Darwinism sees individual
genes as distinct, selfish units, beans in a bag. Yet selection can occur
at many levels: gene and genome, population and entire ecosystem, all
evolve. And there are constraints given by the laws of physics and
chemistry. No assembly of genes can produce a human with wings to fly, not
because we aren't capable of angelic behaviour but because you can't build
a flesh, muscle and bone structure capable of providing enough lift.
Furthermore, fundamentalist Darwinism operates as if there is a simple
linear relationship between 'a gene' and 'a phenotype.' Not so. You can't
read off the complex four dimensions of a living organism (three of space
and one of time) from the single dimension of DNA. Modern molecular biology
knows that genes are not beads on the chromosome chain. they are segments
of DNA, separated by intervening nucleotide sequences without known
function, 'read' by the RNA and protein synthesizing machinery in
complicated ways, with alternative splicing, different reading frames,
editing and post-translational modification to produce the dynamic
constituents of the living cell. in fact DNA is rather an inert substance.
It is not the 'master molecule,' the 'blueprint of life,' the 'code of
codes' or whatever other grandiose metaphor has been proposed. It is
brought to life only in the context of the cellular orchestra of enzymes,
energy flow and the membranes which contain them, the properties studied so
painstakingly by generations of biochemists and now swept to one side by
theoreticians who prefer to model life on a computer than study the real
thing. the DNA egg definitely needs the cellular chicken to function.
Understanding life in four dimensions means that we need to appreciate the
rules of development, why it is that no-one mistakes a human for a
chimpanzee even though we are said to share over 98% of our genes.
Development, by which the single fertilised egg becomes the fully formed
adult, requires that we understand process and dynamism rather than just
the static properties of models. Every molecule in our bodies is
synthesised, broken down and replaced at rates varying from thousands of
times a second to a few times a year, and yet you will instantly recognise
a friend that you saw many weeks ago, and your brain will store memories of
events that occurred decades past. This is why as opposed to the term
homeostasis, a physiological principle you will find in almost every
biology text book, I prefer homeodynamics, to capture this sense of
movement through life's trajectory, which I call a lifeline. the paradox of
development is that at every instant an organism is both being and
becoming. An example: a new born baby has a suckling reflex, by which it
draws milk from its mothers breast. Within months it turns into a child,
with teeth, and eats solid food by chewing. Chewing isn't simply grown-up
suckling. It involves a quite different set of muscles, and the food needs
different enzymes to digest it. Thus the baby has both to be a competent
suckler, and to be at the same time on its developmental way to becoming a
capable chewer. This process of self-construction, sometimes called
autopoiesis, is the antithesis of beanbag theories of genes 'for' this or
that - one of those shorthand phrases which is so easily misunderstood.
the great evolutionary biologist theodosius Dobzhansky once said 'Nothing
in biology makes sense except in the light of evolution.' I think he was
absolutely right, but I want to extent his claim. Nothing, I argue, makes
sense in biology except in the context of history - by which I mean
evolutionary history, developmental history, personal history, and for our
own human species, social and cultural history as well. And in order to
understand it at all we must take into account the history and
presuppositions of our own science, biology.
Don't get me wrong. Take as an example the claim that there are genes 'for'
criminal behaviour. there can be no doubt that there is a relationship
between a person's behaviour and what is going on inside their bodies and
brains. A person committing a crime will experience particular surges of
hormones, particular patterns of neural activity, and these will differ
from person to person and type of act to type of act. Part of this
difference will be accounted for by any person's unique genotype. But what
makes a particular act 'criminal' depends on social conventions, context,
the state of the law and many other features. Was private Lee Clegg,
shooting a teenage joyrider in Ulster when she crossed an army roadblock, a
murderer (as the court found him) or a soldier doing his duty (as those who
argued for his pardon insisted) ? Whichever he was, the genetic, hormonal
and brain processes involved in his aiming and shooting his rifle were the
same. And if we want to know why there are so many vodka-soaked drunks on
the streets of Moscow, it is more relevant to enquire into the poverty and
desperation of living conditions in that society than to study the
molecular genetics of alcoholism.
Good science requires that we ask appropriate questions, which relate to
the determining level for any phenomenon we want to understand. Genes are
not selfish, and cells don't have memory. these are properties that belong
to individuals, not molecules, and the metaphors that pretend otherwise
serve only to confuse.
Steven Rose is Professor of Biology and Director of the Brain and Behaviour
Research Group at the Open University.
http://www.bbc.co.uk/education/darwin/leghist/rose.htm
