13 September 2010
ByAppeared in BioNews 575
It Takes a Genome: How a Clash Between Our Genes and Modern Life Is Making Us Sick
ISBN-10: 013713746X, ISBN-13: 978-0137137466
Buy this book from Amazon UK
I'll admit right from the start that I'm a bit of a waste of time when it comes to science: I dropped most of it at 14 in favour of Latin, and the remainder of my school science was taught by an ageing physicist who spent most of the following 18 months telling a very involved shaggy-dog story about an octopus and some bagpipes. Hence, if I read a science book and understand it, it's either well-written or utterly simplistic. When Greg Gibson, on page two of this book, encourages us to consider a 'simplistic' way of thinking about biology, I hoped he'd made a small mistake and actually means 'simple'. But it's sadly apparent over the course of the next hundred and fifty-or-so pages that he's let the cat out of the bag.
Gibson's hypothesis is the way our species now lives makes us vulnerable to a number of illnesses, which have a genetic component. As Gibson puts it, our genes are out of equilibrium with our lives. That's fair enough at first glance - until a couple of question arise: what is the genetic component of illnesses? And what does it mean to say that our genes and lifestyle are out of equilibrium anyway?
I'll leave that second question for now. Gibson's approach to the first question is to explain how a range of maladies can be tied to certain clear genetic factors. He explains how, for example, a person who inherits a mutated version of the tumour-suppressing gene Rb has a significantly elevated chance of developing retinoblastoma. In other cases of cancer, genes that code for enzymes that could repair 'broken' DNA are themselves broken. Familial colon cancer fits into this group.
So far so good. Gibson's explanation is perhaps a bit basic, but it is reasonable. Things begin to get harder to swallow when he turns his attention to other illnesses. For example, he devotes a chapter to AIDS. But it's not clear what this has to do with genetics or how it's a 'clash between our genes and modern life' making people ill in this case. Gibson's line here is - in a nutshell - that HIV (human immunodeficiency virus) exploits certain vulnerabilities, but some people seem to carry genes that have mutated to minimise the vulnerability.
Of course, this is great news for the people in question; and it would seem hard to deny this insight is likely to prove useful in the hunt for vaccines, treatments and cures for HIV and AIDS (acquired immunodeficiency syndrome). But this doesn't really justify the title of the chapter: 'Genetic AIDS'. It might be that people with a certain gene or mutation can resist HIV infection, but it does not follow that AIDS is a genetic illness any more than it would to say smallpox is a genetic illness because Europeans have a certain resistance the Incas lacked. Without the virus, even the most genetically vulnerable people will not develop AIDS. So it's not a genetic illness or even genetically related in any meaningful sense.
Things are worse still when the discussion turns to depression. The idea there might be a genetic component to mental illnesses like depression is prima facie attractive - but the problem is, as Gibson tells it, investigations into the genetic basis of depression have given us very little. This leads him to claim, bafflingly, that 'Depression is one of the most genetic illnesses there is; yet paradoxically no one has yet found a gene for depression' (p 109). To my admittedly uneducated mind, the second clause of that sentence seems to give us a reason to suspend our judgement on the first.
Maybe he means depression displays heritability - but you can have non-genetic heritability. Wealth is frequently heritable, but that's not genetic. Gibson tries to dig himself out of the hole by saying 'identical twins have about a 70 per cent concordance rate' for bipolar disorder. 'That's maybe a fifty fold increase in susceptibility', he continues, 'by sharing all your genes […] with your twin. Even nonidentical twins have a 1 in 4 chance of bipolar disorder if their twin is afflicted, also heavily implicating the genome' (p 109).
Unfortunately, his argument doesn't work. Genetically, nonidentical twins are no more similar than any other people who share the same parents so it's not obvious what difference is made by being a twin. Maybe things are different for non-twin siblings? But that seems to torpedo the gene hypothesis. After all, what makes a non-twin sibling different from nonidentical twins is not genetic inheritance, but the conditions of gestation and upbringing. Gibson admits this: the words I omitted in the quotation above were: 'and the womb and upbringing'.
Where does this leave identical twins and their concordance rate? Well, perhaps a gene they share - when combined with conditions in the womb and the home - dispose them to bipolar disorder. But that's a long way from saying the disorder is genetic in the everyday sense of the word. Unless and until a gene is identified that's both a necessary and sufficient condition for bipolar disorder, the noise-to-signal ratio will be much too high.
Reading this, my fear is what Gibson means when he says our genes and the environment are out of equilibrium is that our environments and lifestyles frequently cause us to be ill. But that claim - while straightforward enough - doesn't need a discussion of genes at all. Someone who has a variation of a gene may be more vulnerable to certain environmental pathogens another person who doesn't. But that doesn't mean the person's genes are out of balance with his environment - there's no balance to be had at all.
This is a curious book. It's hard to know who it's pitched at. Maybe it's directed at Craig Venter of who Gibson seems to be very fond - he wonders why the Human Genome Project required 'millions of taxpayers' dollars [when the project] turned out to be doable by private initiative' (p 14), without questioning why a private consortium should be allowed to get its mitts on - and privatise - the commons represented by the human genome, and without noting that it was the public project that won the race. But Venter would know all this stuff and Gibson presumably wants to shift more than one copy.
Maybe it's aimed at university-educated adult readers, but he does seem to talk down to them. For example, he feels the need to define 'kindling' as 'the dried small sticks and twigs that we used [to light fires]' (p 119). Wow! Who knew? Elsewhere, though, he assumes a great deal of us: on p 127 he tells us to go and look Notch proteins on the Internet for ourselves. I did, and having understood barely a word Wikipedia told me, am curious to know how Gibson's instruction would be received by people who needed the word 'kindling' defined for them.
Maybe it's aimed at the curious lay reader - people like me. But then his airy, hand-waving explanation of the genetic code as 'consist[ing] of four letters, A, T, G and C, strung together in long molecules of DNA' (p 15) is not enough. Really? Actual letters? Or maybe those letters stand for something?
It'd be nice to have at least a rudimentary explanation of what that something is and how it works - especially when there's so much elsewhere in the book that's pointless. For example, the chapter on diabetes devotes almost 10 per cent of its space to potted biographies of the baseballer Jackie Robinson and of Ella Fitzgerald. Just about every illness considered is prefaced with a list of celebrity sufferers. So what? Shouldn't we have less of this stuff, and much more science? But maybe we have identified the target audience of the book: people who're secretly interested in the diseases of the rich and famous, but who want to look like they're interested in biology.
Buy It Takes a Genome: How a Clash Between Our Genes and Modern Life Is Making Us Sick from Amazon UK.