Richard Dawkins on the nature of the gene
Andy Denis
January 2003
This note argues that the charge of reductionism levelled against Richard Dawkins is
false. It does so by examining the development of his notion of the genes in his books
The Selfish Gene (TSG), and The Extended Phenotype (TEP).
In the history of the last three centuries or so, reductionism has done well by piggybacking on the spectacular success of the natural sciences – a success founded on the
materialist standpoint of those sciences. Holism, on the other hand, has done very
poorly – perhaps in part because of its link with idealism. These associations lead to a
tension in the reflective practice of scientific investigators. The tension can be seen in
Dawkins in the way he looks for some substrate element to which he can reduce
complex phenomena.
We start with Dawkins’s definition of the gene in TSG:
“A gene is any portion of chromosomal material that potentially lasts for enough
generations to serve as a unit of natural selection...a gene has to be a portion of
chromosome. The question is, how big a portion...? Imagine any sequence... Call the
sequence a genetic unit. It might be a unit of only ten letters within one cistron1; it might
be a sequence of eight cistrons; it might start and end in mid-cistron. It will overlap with
other genetic units. It will include smaller units, and it will form part of larger units. No
matter how long or short it is ... this is what we are calling a genetic unit. It is just a
length of chromosome, not physically differentiated from the rest of the chromosome in
any way.” (TSG: 28-9)
We may note two things here: firstly, Dawkins’s desire to find a basic unit to which
all else can be reduced; and, secondly, the fact that his ‘gene’ is physically indistinct
from the rest of the world: it is characterised by what it does, not what it is. Dawkins
proceeds:
“The average life-expectancy of a genetic unit can be conveniently expressed in
generations ... If we take a whole chromosome as our presumptive genetic unit, its life
story lasts for only one generation... If we trace the ancestry of a small genetic unit back
far enough, we will come to its original creator ... The smaller sub-units which make up
the genetic unit we are considering may have existed long before [the creation of the
genetic unit]. Our genetic unit was created at a particular moment ... in ... that the
particular arrangement of sub-units by which it is defined did not exist before that
moment.... But if we consider a very small genetic unit, it may have been first assembled
in a ... distant ancestor, perhaps an ape-like pre-human ancestor.” (TSG: 29-30)
Dawkins concludes his discussion of the gene thus:
“I am using the word gene to mean a genetic unit that is small enough to last for a large
number of generations ... This is not a rigid all-or-nothing definition but a kind of fadingout definition, like the definition of ‘big’ or ‘old’. The more likely a length of
chromosome is to be split by crossing-over, or altered by mutations ... the less it qualifies
to be called a gene... A cistron presumably qualifies, but so also do larger units. A dozen
1
Cistron: a length of chromosome responsible for encoding one chain of amino acids in a protein.
cistrons may be so close to each other on a chromosome that ... they constitute a single
long-lived genetic unit. To be strict, this book should be called not The Selfish Cistron
nor The Selfish Chromosome, but The slightly selfish big bit of chromosome and the even
more selfish little bit of chromosome.” (TSG: 32-3)
So, for Dawkins, what is required is the idea of an atom - ‘indivisible and independent
particles’, and he spends several pages of TSG wrestling with this notion. But at the
end he is unable to locate an ‘indivisible and independent particle’:
“Even a cistron is occasionally divisible and any two genes on the same chromosome are
not wholly independent. What I have done is to define a gene as a unit which ...
approaches the ideal of indivisible particulateness.” (TSG: 33)
“The gene is defined as a piece of chromosome which is sufficiently short for it to last,
potentially, for long enough for it to function as a significant unit of natural selection.
“Exactly how long is ‘long enough’? There is no hard and fast answer.... This is a matter
of quantitative detail which will vary ... The largest practical unit of natural selection - the
gene - will usually be found to lie somewhere on the scale between cistron and
chromosome.” (TSG: 35-6)
So the goal of the independent substrate atom is now simply an ‘ideal’ to be
‘approached’.
We now move on to the connection between the basic unit, the gene, which Dawkins
has defined, and selfishness:
“[A]t the gene level, altruism must be bad and selfishness good. This follows inexorably
from our definitions of altruism and selfishness. Genes are competing directly with their
alleles for survival, since their alleles in the gene pool are rivals for their slot on the
chromosomes of future generations. Any gene that behaves in such a way as to increase
its own survival chances in the gene pool at the expense of its alleles will, by definition,
tautologously, tend to survive. The gene is the basic unit of selfishness.” (TSG: 36)
Having said that, Dawkins steps back to consider the environment of the gene. And
of course, that environment critically contains … other genes. The ‘independence’
which the atomic gene was supposed to ‘approach’ now vanishes completely:
“As far as a gene is concerned ... other genes are just a part of its environment ... the
effect of the gene depends on its environment and this includes other genes. Sometimes a
gene has one effect in the presence of a particular other gene, and a completely different
effect in the presence of another set of companion genes. The whole set of genes in a
body constitutes a kind of genetic climate or background, modifying and influencing the
effects of any particular gene.” (TSG: 37)
This has nothing to do with physical proximity. The effects, and consequently the
fate, of a gene can depend on the presence or absence of genes on different
chromosomes, genes borne by different individuals, and even the genes of other
species:
“[T]here is also a sense in which genes which are in no way linked to each other
physically can be selected for their mutual compatibility. A gene that cooperates well
with most of the other genes ... in ... the rest of the gene pool, will tend to have an
advantage... [T]he ‘environment’ of a gene consists largely of other genes, each of which
is itself being selected for its ability to cooperate with its environment of other genes.”
(TSG: 39)
The goals of ‘indivisibility’ and ‘independence’ are completely abandoned in TEP:
“My unit of selection, whether I called it a gene or a replicator, never had any pretensions
to unitariness ... unitariness is not an important consideration.” (TEP: 86)
“If chromosomes were like bead necklaces... with crossing-over always breaking the
necklace between beads and not within them, you might hope to define discrete
replicators ... containing an integral number of cistrons. But since crossover can occur
anywhere ... all hope of defining discrete units disappears... [W]e are not looking for
discrete units but for pieces of chromosome of indeterminate length which become more
or less numerous than alternatives.”
“Natural selection can cause changes in frequency only at nucleotide loci ... It is changes
at the single nucleotide level that are responsible for evolutionarily significant phenotypic
changes ...”
But, he says, it would ‘absurdly reductionistic’ to ‘write a book called The Selfish
Nucleotide’.
So much for discreteness, indivisibility, particulateness. What about Independence?
RD goes out of his way to stress that when we speak of ‘a gene for’ something, such
as tying your shoelaces (TEP: 22) we really mean ‘a genetic contribution to variation
in’ tying shoelaces. ‘Variation’ is a key point here:
“a genetic replicator is defined by reference to its alleles ... It is a fundamental truth ...
that whenever a geneticist studies a gene ‘for’ any phenotypic character, he is always
referring to a difference between two alleles.”
There is no presumption that the contribution just mentioned resides at a specific
locus on a specific chromosome and that that is what that bit of chromosome is “for”.
On the contrary, talk of genes ‘for something’ is just convenient language:
“the use of single-locus models is just a conceptual convenience... When we use singlegene language ... we do not intend to make a point about single-gene models as against
multi-gene models... Of course we shall eventually have to face up to multi-locus
complexity.” (TEP:21-22)
Hence what a gene does, what it is a gene for, is function of its relationship with the
rest of the genome: it is a social relation between nucleotide sequences. So we can
say good-bye to any mechanistic, reductionist reading of function from particular
sequences of nucleotides taken in isolation. We cannot say ‘Ooh look, adenine
instead of cytosine at location number 30,004: that’s the gene for homosexuality.’ But
we might be able to say: this particular constellation of nucleotide sequences at
various locations on a number of chromosomes, given the rest of the genome is
unchanged (ie invoking the ceteris paribus condition), and in contrast to a specific
alternative constellation, is a gene for homosexuality. But change the rest of the
genome, or the allele you are comparing it with, and the constellation might generate
wholly different phenotypic effects.
All this says that a gene is not something tangible that you can point to
unambiguously under the microscope. On the contrary, it is a relation, indeed, a
teleological entity:
“The whole purpose of our search for a ‘unit of selection’ is to discover a suitable actor to
play the leading role in our metaphors of purpose. We look at an adaptation and want to
say ‘It is for the good of ...’. Our quest ... is for the right way to complete that sentence...
I am suggesting here that, since we must speak of adaptations as being for the good of
something, the correct something is the active, germ-line replicator.”