For humans at least, to live is to experience. How can we understand
this? One thing is clear: experience is grounded in matter. The connection
is there for us to draw. But drawing it is quite a complicated task.
And, alas, complexity is uncomfortable, so we are inclined to ignore
it. That tends to happen, for instance, when we try to tease out the
linkage between human experience and material reality. We say, ‘It’s
pretty simple, really’. But it isn't’t.

Introducing the Silmans

Consider an example. Before writing this page, I relaxed by listening
for the first time for a long time to one of my favourite pieces of
music: the piano trio in E-flat major by Schubert. I put the CD into
my player and lay down on the sofa. As the music entered the slow
movement, I cried.

The emotional effect of this piece of music, which I first heard live
in a concert, is always very strong. We must all have our favourite
pieces that have this effect on us. The effect does not always depend
on the music itself. It can also depend on the context, the people we
were with, and the significance of the event in our lives.
So, what caused me to cry?

Imagine some space travellers watching this scene. They are creatures
from a world in which silicon replaces carbon. So let’s call them
Silmans. They have some of the characteristics associated in science
fiction with ‘androids’. They notice the crying. They record the
sound waves in the room. As scientists, they trace the sequence of
cause and effect, back through the loudspeakers, the amplifiers, the
laser disc reader, right down to the CD itself.

One of them does a Silman version of ‘Eureka!’ ‘I’ve found it’, he
says, as he explains to his colleagues that the whole effect is caused by
some highly specific digital information on the CD. Another of the
Silmans is nevertheless sceptical. ‘How’, he says, ‘could just a bunch of
numbers have this effect?’

The discoverer counters the scepticism by pointing out that this is
the lowest level of the chain of cause and effect. Without the digital
information, there would be no music, no emotion. Moreover, if you
play around with that information, ‘mutate’ it as it were, by playing it
too fast or too slow, or playing it backwards, transposing sections, or
even transposing bits from another CD, then the person in the room
no longer cries. In fact he may angrily turn the machine off and even
throw the disc away.

There is an inevitable and mechanical chain of cause and effect
here. Any experiment the Silmans might do would reinforce the oneway
nature of this chain. Different amplifiers, speakers, and other
gadgetry can replace everything except the highly specific digital
information on the CD. Surely, then, they conclude that this is the
cause of me crying.

Of course, we know better. We would say that the causes of my
crying include:
• Schubert, because he wrote the music;
• the piano trio, because they played it with such heart-tugging
inspiration;
• and the beautiful context in which I first heard the music and
first cried as a result of it. This, we would say, is in my memory
and forms the emotional context.

We would say that the digital information on the CD is just a way of
capturing the moment, as accurately as possible, and making it
possible for me to recreate, partially at least, the original moment. We
know also that the information could be coded in many different
ways, including analogue encoding in the form of a vinyl disc. It is just
a database that enables the music to be stored and recreated.
In short, we would have no difficulty at all in laughing at the
stupidity of our Silman visitors from another planet. They saw a
simple explanation, we would say, and grabbed at it. How stupid!
Well, we should be careful whom we laugh at. For we, too, get trapped
in simplistic explanations.

DNA-mania

Indeed, there is a popular dogma that is reinforced daily in the
media––and, it must be said, by many scientists––that rests on a crude
mistake, just like the Silmans’. André Pichot1 has called this DNAmania.
It is the delusion that the DNA code ‘causes’ life in much the
same way as the CD ‘caused’ my experience of the Schubert piano
trio.

The analogy is obvious. The human genome is in some ways a little
like a CD. It carries digital information. Let’s quickly summarise how.
The genome is all the chromosomes in a cell. A chromosome is a long
DNA molecule and some associated proteins. It is conventionally
divided into genes. A gene is a section of DNA that is used in
producing a particular protein.

DNA is composed of four chemicals (nucleotides), generally
referred to by the letters A, T, G, and C.2 There are two strands of
DNA in each chromosome, wrapped around each other in a
double helix. It was the discovery of this double helical structure that
formed Watson and Crick’s Nobel Prize-winning work in 1953. The
nucleotides in one strand always lie opposite those in the other
according to the rule: A goes opposite T, G opposite C. Two such
complementary nucleotides make a base pair. The genome is 3 billion
base pairs long. These form 20 000–30 000 genes.

In each gene, the chemicals are arranged in specific ways to
facilitate the production of specific proteins. Every time a protein is
needed, the appropriate chemical ‘code’ is ‘read off’ the gene; this
gives the pattern of chemical elements that will make that protein
what it is. Our genes encode the sequences of the 100 000 or so
proteins that make up the human body. No protein is made that is not
coded for by a gene. So the genome is important. After all, proteins
are crucial for life.

A living cell is a continuing, action-packed drama. Molecules
interact and change. One change triggers another, and so on and on.
Complex chains of molecular interaction happen again and again. We
call them ‘pathways’. There are cell cycle pathways, which correspond
to the cell ‘ticking over’. There are developmental pathways,
because cells grow, divide, and form more cells. There are all sorts of
regulatory pathways. And proteins form the backbone of all these
biochemical pathways.

Cells organise into tissues, such as skin, bone, muscle, to form
organs such as the heart and kidneys, and finally, all these, together
with the immune and hormonal systems, form the organism, the
whole animal. This operates in many different ways, at various levels
of organisation. And all of this ‘function’, as biologists say, involves
proteins.

The causality seems to be entirely one-way. The DNA causes the
proteins, the proteins cause the cells, and so on. The organism itself is
just what shows on the outside; what is really happening, the inside
story, is that the information coded in the genes is being expressed. In
biologist-speak, the phenotype is ‘created by’ the genotype. The story
is seductive.

We have fitted ourselves out with a magnificent set of blinkers. We
have rendered ourselves incapable of looking at the relationships
between the genetic code and living systems in any other way.
This chapter asks why.

• Why are we so fond of the gene-centred view? We can explore
this question by examining a classic and very popular statement
of this view––Dawkins’ 1976 description of the ‘selfish gene’.

• How did so many people come to interpret this view as genetic
determinism? That question is particularly important since, as I
will show, it is not that of Dawkins himself. Let us then explore
the historical context, out of which DNA-mania has developed.
We start with the reductionist causal chain. This is the ‘inside story’
that we have just discussed.

The chain runs upwards. It is a ‘one-way’ system, from the genes to
the organism. The idea is that, if we knew all about the lowest-level
elements, genes and proteins, then everything about the organism
would be clear to us. We could work out what happens at the higher
levels, and explain it completely, in terms of our low-level knowledge.
We could reconstruct the whole organism from the bottom up.

The first step in the chain is fainter than the others because it
represents a rather different causal relationship. At each stage above
this one, we are talking about physical causes––how one chemical
reaction leads to another. But at the first stage something different is
happening, over and above the physical causation of the chemical
reactions involved. It is generally described as the reading of a
code. There is transcription and translation of the code. This code is
sometimes called the blueprint of life, or the program of life, following
Monod and Jacob’s colourful idea of ‘le programme génétique’
(Monod and Jacob 1961; Jacob 1970).

So much for the diagram. The problem with it is that it shows only
half the story. When we get to Chapter 4, we shall see how much it
misses out. But for the moment let us assume it is as comprehensive as
it is supposed to be.

On that assumption, then, let us ask: does the causal mechanism
work in the way that is represented here? By no means!

Problems with genetic determinism

Genes are coded as DNA sequences. It is these sequences that are
replicated and passed on to future generations. So biologists also call
genes replicators. Gene determinism somehow sees them as causal
agents. How can that be? After all, what does DNA do? As biological
molecules go, not much. The real players in the action of life are the
proteins. They are the really active molecules. They indulge most in
the biochemical processes necessary for life to occur. DNA is in
comparison rather passive.

Proteins are produced in tiny factories inside the cells of the body.
Biologists call them ribosomes. These factories get going when they
receive a message that ‘tells’ them to make a certain protein. Each
such message is generated using DNA. A DNA sequence that corresponds
to the relevant protein sequence is copied onto another molecule,
appropriately called a ‘messenger’, which transmits a form of
the sequence to the ribosomes. The messenger molecules, called messenger
RNA (ribonucleic acid), are another kind of nucleic acid
sequence. The DNA sequences are therefore a kind of template, a
specific sequence of nucleotides that can be transcribed to produce
the message that is then translated into an amino-acid sequence when
the protein is made. (Amino acids are the units of which protein is
composed, just as nucleotides are the units of which DNA is
composed.)

That process is called ‘gene expression’. This terminology gives the
impression that the whole process is implicit in the gene, or at least in
the information that the gene holds, which simply needs to be
‘expressed’.

But it is a little odd to say, as we often do, that the DNA sequence
‘determines’ the protein. In fact, the DNA just sits there, and
occasionally the cell reads off from it a sequence that it needs, in order
to get some protein produced. This looks very much like my hi-fi
equipment reading the digital information on a CD to generate the
real ‘action’: the music. So the first step in the reductionist chain of
cause and effect is not a simple causal event at all. When a sequence is
read off, that is an important event, which initiates a whole series of
subsequent events. These are physical events. True. But it is the
process of reading that matters, as well as the object that is read.
This process involves certain systems of proteins. If we wish to
identify an agent of the action, it must be those systems. They ‘read’
the DNA code. DNA does nothing outside the context of a cell3
containing these protein systems, just as the CD can do nothing
without the CD reader. So, we have the paradox that proteins are
required for the machinery to read the code to produce the proteins. I
will return to this paradox in later chapters.

From "the Music of Life - Biology beyond the genome" Denis Noble