Is intelligence genetically determined? You might think so, if you saw the headline-grabbing from UK education advisor Dominic Cummings. The 240-page essay was a parting gift to his boss, education minister Michael Gove. In claiming that educational ability is largely inherited, he reignited an old controversy that many thought had been put to rest.

The heritability claim depends on two assumptions: that we can define and measure intelligence; and that we can unpick the contributions of genes and environment.

Attempts to measure intelligence stretch back to early last century, when the French psychologist Alfred Binet devised a series of tests for schoolchildren of different ages, to help teachers identify those who could benefit from extra help. Defining the average score for each age as 100, he then compared the performance of each child with the average for their age group to calculate the child’s Intelligence Quotient, or IQ.

By the 1920s, however, tests had been developed for adults and their purpose had changed. They were now believed to provide a fixed measure by which a person’s capacity could be rated against others – no longer a way of helping, but of defining.

IQ had become a surrogate measure, a linear scale along which everyone could be grouped as if by height. IQ theorists insisted that it captured a genuine and fixed unitary property, located somehow in the brain.

Elastic IQ

However, unlike height, which can be measured absolutely with a ruler, the IQ scale is more like a piece of elastic, to be stretched to fit social expectations and adjusted accordingly. Despite attempts to develop tests that apply across all cultures, they inevitably reflect assumptions about what constitutes “correct” answers and about how people should perform.

Thus test questions are devised to ensure that on average boys and girls score similarly, but when in the same tests middle class children scored better than working class, and in the US white students outperformed African-American, this was assumed to reflect real differences. It didn’t.

Unsurprisingly, IQ test scores correlate with school performance (and with parental socio-economic status), because this is what they are designed to do, but they only weakly predict a person’s future career success. This, as critics were quick to point out, is because IQ doesn’t capture such elusive features as practical intelligence, creativity, emotional intelligence, social intelligence, musical or artistic talent… the list goes on.

Less rigid psychometricians began to speak of multiple intelligences. Furthermore, neuroscientists, well aware that the processes involved in intelligent behaviour must include perception, attention, memory and reaction speed, have always been sceptical that it can be reduced to a single measure or brain process.

Does intelligence, however we define it, depend on genes? The answer is trivially obvious: yes, absolutely – as does everything else in a living organism. But, as with everything else, it also depends on the environment within which the developing child grows. The question which has obsessed genetic determinists is whether it is possible to partition out the effects of genes and environment.

Heritability equation

Before modern genetics, researchers developed an equation, dubbed heritability, which attempted to do just this. As with IQ, heritability isn’t an absolute measure. Instead, it describes the contribution that genes and environment make to the variance of some trait – for instance IQ – around the mean for the population. To put it in the form of an equation, if V is the variance, G the genetic contribution and E the environmental one, then V = G + E + (GXE). Put simply, genes and environment are supposed to work additively with a small component (GXE) for their interaction.

It is from this formula, and comparisons of IQ scores between identical and non-identical twins, that psychometricians have by and large settled on a figure of 50 per cent for heritability. , Gove’s behavioural genetics advisor and a prominent spokesman for this technique, puts it higher, at around 70 per cent. This is the figure cited by Cummings.

However, the calculation is almost meaningless. It depends on there being a uniform environment – fine if you are studying crop or milk yields, where you can control the environment and for which the measure was originally derived, but pretty useless when human environments vary so much.

Thus some studies give a heritability estimate of 70 per cent for children in middle class families, but less than 10 per cent for those from poor families, where the environment is presumably less stable. And it is a changing environment, rather than changing genes, which must account for the fact that the average IQ scores across the developed world have increased by some 15 points over the past century, to the puzzlement of the determinists.

Untenable assumptions

But even more importantly, the calculation only works if the interaction between genes and environment, GXE, is small. Forty years ago this might have been a reasonable assumption. But despite the efforts of Plomin and his colleagues, it has become untenable in the light of the new genetics that arose from the sequencing of the human genome.

Not only are complex behavioural traits affected by many hundreds of genes, but there are multiple interactions between them and with the environment during development – the burgeoning science of epigenetics. This is why attempts to locate significant genes through scanning techniques called genome-wide association studies, which cannot trace these developmental interactions, have failed.

Earlier this year, a attempted to find genes associated with educational attainment. Their conclusion? The genes they located accounted for a mere 0.02 per cent of the difference in attainment – about 1 month of schooling.

DNA samples from some of Plomin’s subjects have now been sent to the world’s biggest DNA facility, the Beijing Genetics Institute in China, for full genome sequencing, but the failure of previous gene scanning studies to yield anything of genetic or educational interest suggests that this too will prove a vain hope. Leading geneticists have begun to speak of “missing heritability”, of a “black hole” in heritability studies.

Whatever intelligence is, these failures show that to hunt for it in the genes is an endeavour driven more by ideological commitment than either biological or social scientific judgement. To suggest that identifying such genes will enable schools to develop personalised educational programmes to match them, as Cummings does, is sheer fantasy, perhaps masking a desire to return to the old days of the 11 plus. Heritability neither defines nor limits educability.

THESE days we can’t escape from molecular biology—neither its
achievements nor its hype. From cloned sheep to sterile corn, we are surrounded
by more or less informed debates about what its effects will be. So I often have
to remind myself just how young a science it really is. As recently as the
1960s, biochemists regarded it as a cuckoo in their nest—a contempt
immortalised by nucleic acid pioneer Erwin Chargaff, who referred to Crick,
Watson and their successors as “practising biochemistry without a licence”.

Molecular biology is growing so rapidly that the half-life of papers is but a
few months, and students and postdocs rarely read or refer to anything published
more than three years ago. Not surprisingly, a science that has grown so fast
needs, but has rarely found, time to understand its own history. Instead, it
trades in myths about its past. So three new books written by biologists, rather
than professional historians, that attempt to get beyond these myths are
welcome.

While all three cover the same ground, their approaches could hardly be more
different. Traditionally, scientists writing about the history of their subject
describe a steady progress from darkness and mystery into the light of reason,
achieved by men (sic) of brilliance conducting crucial experiments. Such
complacent accounts are interspersed with random and often apocryphal anecdotes
about the researchers themselves. Worse still, they are largely
“internalist”—that is, they treat the science as self-contained, as if it
were not influenced by wider social currents or by funding priorities, although
they accept the importance of technical advances, such as the ultracentrifuge,
electron microscope and electrophoresis.

Ulf Lagerkvist is a medical biochemist, and DNA Pioneers and Their
Legacy is very much in this mould. It begins with a claim for the
traditional values of science as the pure search for truth by dedicated and
poorly rewarded individuals. It ends with a personal account of working with
Arthur Kornberg, who discovered DNA polymerase, a key enzyme in DNA metabolism.
I found this an unchallenging read, designed to inspire young (male—women
appear only insofar as they are wives and helpmeets to the great men)
researchers to enter the field. Crucially, for me, Lagerkvist’s internalist
account is untouched by the more critical approach to the growth of scientific
knowledge that comes from historians, philosophers and sociologists.

The other offerings are quite different. Both Stanley Shostak, a
developmental biologist, and Michel Morange, a biochemist, have spent a great
deal of time immersed in the writings of science’s critics. From the historian
and philosopher Thomas Kuhn to French postmodernists, these critics have
challenged science’s claims to be a way of determining definite (if revisable)
truths about the world. They, in turn, have been vociferously counterattacked by
the defenders of the “true faith” of science.

In Death of Life Shostak has produced an impassioned polemic against
the “chemists and physicists” who have entered biology. In the name of molecular
biology, they have destroyed what is to him the essence of our
science—respect for and understanding of living processes. He scolds
“reductionists” as those who, in the words of William Wordsworth, “murder to
dissect” and lambasts those who are more interested in payoffs in the forms of
Nobel prizes, money and power than in scientific advance.

He argues that molecular biologists suffer from a delusion (he calls it
“delirium genetica”) that the unfolding of living processes in the four
dimensions of space and time can be read off the one-dimensional strand of DNA.
To cure molecular biology’s illness, he argues for a form of neo-Lamarckism,
drawing on ideas ranging from Stuart Kauffman’s self-organising networks of
mutually-catalysing reactions, James Lovelock’s Gaia hypothesis, to the
postmodernist philosophy of Jacques Derrida.

As I share much of Shostak’s distaste for crude reductionist ideology, I had
expected to be much more in sympathy with his account than with Lagerkvist’s.
Sadly, this is the kind of book which gives this kind of book a bad name.
Shostak is so angry he is incoherent. He fails to explain the relevance of the
postmodern stuff, and jumps from context-free internalist descriptions of key
experiments into what are frankly just tirades. His editors have served him
poorly; words are misspelt and material repeated and sometimes contradicted from
chapter to chapter. A pity, because there are important themes buried here.

It was with relief, then, that I turned to Morange’s well-researched and
clearly written A History of Molecular Biology, which appeared in French
in 1994 (elegantly translated by Matthew Cobb). Morange begins his story later
than the others: after a brief establishing chapter, he opens with the
hypothesis, proposed by George Beadle and Edward Tatum in 1941 that each gene
produces precisely one enzyme, and concludes with Kary Mullis’s 1983 invention
of PCR, the polymerase chain reaction which makes multiple copies of a DNA
strand.

Like Shoskak, Morange is critical of the triumphalist and reductionist claims
of molecular biology, and ends the book by reflecting on its place in the life
sciences. Writing from Paris, he is able to stand back from the orthodox story
with its focus on “les Anglo-Saxons”, giving credit to others such as Nobel
prizewinners such as André Lwoff, Jacques Monod and François
Jacob.

His method is to separate out particular themes in the history of molecular
biology—the breaking of the DNA code, the influence of the Rockefeller
Foundation’s funding priorities, or the school of non-biologists grouped around
Max Delbruck, who shared his conviction that the way to study biology was to
examine the simplest possible systems, the phages which infect bacteria. Some
chapters tell an orthodox internalist story, some are punctuated with historical
vignettes, and others are more socially and philosophically framed. The result
is a bit disjointed, but where there are so many different styles of history to
be told, this may be the only way for a nonhistorian to do it.

En route Morange makes some interesting re-evaluations. He discounts the
experimental achievements of the Delbruck school, claiming that their
findings—even the famous Hershey-Chase experiment identifying DNA and not
protein as the hereditary material—were either minor or merely
confirmations of what was known already. What he praises is their role in
setting a research style and bringing the physicists’ confident reductionist
clarity of thought to biology. And he re-establishes the prophetic significance
of Erwin Schrödinger’s famous 1945 essay “What is Life?” in which he
claimed that the hereditary material would turn out to be a “giant aperiodic
ł¦°ů˛â˛őłŮ˛ą±ô”.

Altogether, for a sophisticated theoretical and technical account of the
strengths and weaknesses of the claims and the history of molecular biology,
Morange’s book will take some beating.

THIS is not a modest title, and How the Mind Works is not a modest book. But you’ll have to read it. Its author, Steven Pinker, is a cognitive psychologist, and was once a disciple of the linguist Noam Chomsky but has long since dropped his pilot. His present guides, as he tells us frankly, are the evangelists of the new school of evolutionary psychology, a field still more familiarly known by the name its protagonists disavow, sociobiology.

Pinker’s 660 pages aim to convince his readers of two distinct theses. First, that the human “mind” has evolved as a device for enhancing human survival and reproductive success according to the ultra-Darwinian principles adopted by his new gurus; and secondly, that it is best conceived of not as a single coherent unity, but as an interacting community of distinct modules, each specialised for a particular function. As he makes clear, neither idea is original; rather they synthesise themes derived from his past and present mentors.

No biologist will have much trouble with the claim that humans, with all our attributes – behavioural as well as physical – have been honed to our present form at least in good part by natural selection. The devil, as usual, is in the detail.

Pinker’s approach is straightforwardly mechanistic. If you regard “the mind” as a machine, you can apply the technique used by engineers to discover how a rival firm has built its equipment – so-called reverse engineering. The trouble with reverse engineering “the mind” is that we have to agree what this ambiguous term means. Also – unlike with any human artefact – when we have constructed a story about how the mind might have arisen, we have no way of testing it out. Evolutionary stories are, almost by definition, Just So stories, like Rudyard Kipling’s explanation of how the elephant got its trunk.

Although Pinker is aware of the fallacy of assuming that every biological feature is adaptively designed through an infinitely flexible, all-wise natural selection, he frequently ignores his own caveats. Considering the tortuous route human seminal ducts take from the testes, up through the body and across the urethra to the penis, he explains this on the well-known (but Kiplingesque) grounds that “the testes of our reptilian ancestors were inside their bodies. The bodies of mammals are too hot for the production of sperm, so the testes gradually descended into a scrotum.”

I’m reminded of the joke: if Superman is so clever, why does he wear his underpants outside his trousers? If natural selection is so clever, why not evolve sperm that survive at the higher temperatures, rather than the ungainly and hazardous physical control system that was adopted? Almost certainly either because of contingency – the chance events that Stephen Jay Gould evokes in his rich account of evolutionary processes in Wonderful Life – or because there are other design constraints on what can or cannot be achieved by natural selection. That is, natural selection does not operate in a world without restrictions, à la carte, but is limited to a table d’hôte choice from a few options.

Minds are inextricably connected to brains, and biologists approaching Pinker’s questions find themselves discussing the structure, function and evolution of the brain, about which it is possible to obtain more empirical evidence than can be discovered through Just So reverse engineering.

Pinker is not very interested in actual brains: as he says, his mental “modules” may or may not map onto actual neuronal ensembles. His “mind” is constructed not as a unified coherent centre of conscious thought, emotion and action, a product of the inextricable interplay of biology and culture, but as a sort of Swiss Army knife. It is a compressed miracle of pull-out devices, if not for taking stones from horses’ hooves, then for seeing stereoscopically (a large section of the book, and in many ways its best, is concerned with visual perception) or speaking grammatically. Each module, Pinker argues, extending a theme from his earlier book, The Language Instinct, has evolved separately and operates semi-autonomously, although in the interests of the genes that created it.

The megaphone diplomacy of the dustjacket proclaims this “the best book ever written on the human mind”. So vulgar a dismissal of several thousand years of human science and philosophy reflects only the intellectual and cultural impoverishment of this way of thinking. Pinker’s “mind” is definitely a machine, a point echoed on the book jacket with its design of little springs, cogs, nuts and widgets. It is the sort of abstraction that computer engineers used to program into their machines when exploring artificial intelligence and, like a computer, deals with “information”. But real brains deal with meaning, meaning given to sensory inputs by the working of the brain, based on experience provided through evolutionary and developmental history.

Similarly, his “genes” have little to do with real strands of DNA: they are the theoretical entities made notorious by Richard Dawkins. Hence, just as for his mentors, each module or piece of behaviour is constructed by and in the interests of genes. But real humans, like all other living organisms, grow and develop, creating themselves through the dynamic interplay of DNA, the cellular orchestra in which DNA is embedded, and the larger world outside. Modularity, if it exists, emerges dynamically. Pinker’s organisms are biological abstractions: his mental modules spring fully formed and unmediated from preformative genes, each presumably containing a miniature blueprint for a particular implement within the Swiss Army knife ensemble.

So what are these modules? Pinker, following the Californian duo Leda Cosmides and John Tooby, argue that they evolved to suit humanity’s Stone Age existence, to help our ancestors to survive as social animals, to lie and swindle convincingly, while being able to detect lying and swindling in our neighbours, and by murdering our stepchildren but protecting our genetic kin. The Stone Age they portray has something of the Flintstones about it – American suburban mores transported into the dim past. Indeed, he argues that evolution of brains and behaviour stopped in the Stone Age, even though elsewhere he points out that the time that has elapsed since then would be adequate for dramatic changes to both.

The evidence for these claims is limited to a couple of overinterpreted anthropological observations and a rhetorical attack on all those who dispute them, a series of straw people variously identified as Marxists and feminists. In so far as I am familiar with the work of those Pinker derides (including my own), his caricatures suggests that he has scarcely read, still less attempted to understand anything we have ever written.

What I find very odd about all this macho evolutionary talk, with its wild speculative finale on “The meaning of life”, is the extent to which, in the last analysis, it wants to have its cake and eat it. We are, evolutionary psychology argues, merely the deterministically driven products of our selfish genes and their sole interest, replication. All our deepest desires and emotions, our abjectly selfish failures, as well as our most selfless ambitions to create a more beautiful world, are simply shadow play. Yet at times Pinker, like Dawkins and others, recoils from this bleak vision. He is in some unexplained way independent of his genes: as he puts it, if they don’t like what he does, his genes can go jump in the lake.

But where then does this autonomy come from? A richer understanding of biology than Pinker’s helps us understand that it is indeed our genes, as part of the living dynamic processes in which they are embedded, which enable us to be free, albeit in circumstances not of our own choosing.