What Scientists Think

Jeremy Stangroom, Jeremy Stangroom

• Publisher: Routledge
• Year: 2005
• ISBN:
  9781134314263
• Edition: 1
• Topic: Philosophie
• Subtopic: Geschichte & Theorie der Philosophie

What are scientists working on today? What do they worry about? What do they think about the working of the brain, climate change, animal experimentation, cancer, and mental illness? Is science progressing or in retreat? Is this century humankind's last?These are just some of the compelling and provocative questions tackled here by twelve of the world's leading scientists and scientific thinkers. In engaging and lucid discussion, they clarify many of the most urgent scientific challenges and dilemmas facing science today.

Essential reading for anyone interested in popular science, What Scientists Think is edited and written by Jeremy Stangroom of the highly successful The Philosopher's Magazine and includes a foreword by Marek Kohn, author of A Reason for Everything: Natural Selection and the British Imagination.

1
Darwinism and Genes

In conversation with Steve Jones

In his book The Blind Watchmaker, Richard Dawkins argues that prior to 1859 it was not really possible to be an intellectually fulfilled atheist. The difficulty for atheism was that the complexity of the living world, in the absence of an alternative explanation, suggested the hand of a designer at work. However, this all changed in 1859 with the publication of Charles Darwin’s The Origin of Species, which brought to the world’s attention perhaps the most powerful single idea in the history of science: namely, the idea of the evolution of species by the mechanism of natural selection.

Broadly speaking, this idea has it that natural selection works on the variations in the inherited traits of organisms, by ensuring that those traits which are most likely to promote reproductive success–for example, by helping an organism stay alive long enough to breed–are those which are most likely to be passed on to offspring, and which will, therefore, become predominant. However, in 1859, a problem for Darwin’s theory was that the mechanisms of inheritance were not yet understood.

‘Darwin got inheritance fundamentally wrong,’ says Steve Jones, Professor of Genetics at University College London (UCL). ‘In fact, it’s actually rather hard to know precisely what he thought about it. Nineteenth-century biologists weren’t really that interested in theories of inheritance. They were more interested in development; how, for example, an elephant’s egg, which is a small formless piece of protoplasm, develops into an elephant.

‘But Darwin did have this idea that there were gemmules, bits of information, which floated in the blood, and which were mixed at conception and then passed on. But after the publication of the first edition of the Origin, a Scottish engineer, Fleeming Jenkin, wrote to him, and pointed out, roughly speaking, that if you mix red and blue, you get purple. You can never get either red or blue back again. So if it were advantageous to be red, the advantage would be lost as soon as it was mixed; any advantageous character would be diluted out.

‘Darwin was that rare thing, an honest scientist, and he saw at once that this was a fatal flaw in his argument. So you find that the later editions of the Origin are less sure, less mature. But, of course, it turned out that the flaw wasn’t a flaw at all. Just a couple of years after the Origin, Mendel showed that inheritance was based on particles, not fluids, and that inheritance is detached from the physical structure of the people who pass on the genes. And this rescued Darwinism, because you can get the red gene back, even from a purple individual.’

We now know that genes are the units of biological inheritance. People often talk as if genes code for particular characteristics in a straightforward way. So, for example, the media have made much of the possibility of a ‘gay gene’; and people will talk about genes for particular illnesses, for instance a gene for schizophrenia. But aren’t things actually a lot more complicated than that?

‘Yes, they are,’ Jones replies. ‘In some ways, this is to go back to the nineteenth-century question about development; it is about the relationship between genotype and phenotype. Every geneticist knows that there is not a straightforward mapping between genotype and phenotype; we know this so well that we don’t talk about it. But the general public don’t realise it, and they use the most dangerous word in genetics, which is the three letter word, ‘for’: a gene for this and a gene for that.

‘There is something right about this way of talking. If, for example, a person has one particular DNA chain, then they will grow up as an achondroplastic dwarf. In shorthand, that DNA chain is a gene for dwarfism. But this is unusual. For most of the attributes which we find interesting–for example, things like personality and appearance–there are very few single genes where there will be a direct relationship between a genetic change and a phenotypic change.’

If that’s the case, how is it possible to specify an individual gene? What actually gives a particular DNA chain its reality as a gene?

‘That is not an easy question; it’s a technical issue, and there isn’t necessarily a right answer,’ says Jones. ‘Roughly speaking, a gene can be defined as a unit of information. That’s how Mendel saw it. Biochemically, it’s a segment of DNA, which produces an RNA message which is read off it. But now that we know more about the genome, the old central dogma, that genes make RNA makes protein, is by no means straightforward. For example, there are genes within genes, some genes overlap with each other, and there are great acres of DNA, called “junk DNA”, which doesn’t seem to do much at all. So “gene” is a convenient shorthand for what may turn out to be a rather complicated phenomenon.’

Are those philosophers who claim that there is a lot of confusion in the use of the word ‘gene’ then right in their criticisms?

‘I don’t think biochemists are going to be the least bit interested in what philosophers think about genes,’ Jones replies. ‘As I’ve said in the past, philosophy is to science as pornography is to sex: it’s cheaper, easier and some people prefer it. But there is this rather philosophical point in biology that the more you find out, the more complicated things get. We’re very much in the position of finding out stuff, and then finding the exceptions to what we think we know. So at the moment what a gene is isn’t exactly clear.’

The language of ‘genes for’ particular characteristics causes quite a lot of friction. Both Richard Dawkins and Ed Wilson, for example, have felt the need to defend its use. Does Jones think that it is a sensible way of talking or does it involve the potential for too much misunderstanding?

‘I think it is a useful shorthand, and so long as you have your fingers crossed when you use it, then it’s probably OK,’ he answers. ‘There are certainly genes for lung cancer, for example. If everybody smoked, then lung cancer would be a genetic disease; a person’s ability to cope with the poisons in tobacco is very much a matter of the genes which they’ve inherited. But it would be foolish to say that the genes for lung cancer are independent of people’s smoking habits. They interact. So the word “for” has a nimbus of other meanings around it. Matt Ridley, in his book Nature via Nurture, makes the point that geneticists don’t actually talk about the nature/nurture controversy, because they know it’s not a controversy; there is both nature and nurture, and it is very difficult, if not impossible, to untangle the two.’

In his book Almost Like a Whale, Jones argues that ‘every part of Darwin’s thesis is open to test. The clues–from fossils, genes or geography–differ in each case, but from all of them comes the conclusion that the whole of life is kin.’ How, I ask, does our understanding of genes contribute to this conclusion? Is the key point that we can identify genes, or at least chains of nucleic acids, which different species or organisms share in common?

‘Well, that’s one of the key things, but there are others,’ he replies. ‘Modern molecular genetics is really just comparative anatomy plus a huge amount of money. Darwin’s arguments were underpinned by his undoubted skills as an anatomist. He looked, for instance, at many kinds of barnacles, and he found that despite a huge variation in their appearance, they are built fundamentally the same way. With much less skill you can now do this with any group of creatures. For example, if you’re looking at the genes which increase life expectancy in the dros-ophila, it is possible to go to a database to look for the same genes in humans, and what you find is that in humans they function to repair DNA damage. So you know that life expectancy and DNA damage are related. This tells you that the plans for building things as different as a fruit fly and a human being are actually quite similar. So what genetics has done is to introduce improved weapons to the Darwinian argument.’

A resolute anti-Darwinian, of course, is unlikely to be convinced by this line of argument. If they were a creationist, for example, then likely they’d say that it would be expected that God would use similar mechanisms to build different organisms.

‘That’s a different kind of point,’ says Jones, when I put it to him. ‘I’m like Richard Dawkins in that I won’t debate with creationists, because they’re not engaging in rational argument. Certainly it is possible to say, “Well, God would have done that”, but that’s the equivalent of Philip Gosse’s argument that fossils might have been put into rocks by God in order to test the faithful. Well, maybe that’s right, but until there is some evidence to support the view, I’m not going to believe it.’

A different kind of challenge to Darwin’s idea of natural selection comes from those people who claim that the fossil record suggests that evolution proceeds in fits and starts rather than by means of slow, gradual change.

‘This is a real argument, and happily it’s one which takes place between biologists,’ Jones says. ‘Steve Gould wrote a paper called “Is a new and more general theory of evolution emerging”, in which he pointed out that even the best fossil records show apparent leaps from one form of organism to the next. Darwin had made a real song and dance about the fact that nature does not make leaps. He did this in order to avoid the creationist model which allows that a species might turn instantly into another species. Darwin’s claim was that the incompleteness of the fossil record explained the kind of thing which Gould identified. But Gould insisted that it was a real phenomenon; that once you get a particular form, it is very hard to get from that form to another one. You had to go through a revolution, which would involve all kinds of disruption, gene interactions, bottlenecks, and so on. This is an interesting argument. Gould certainly made the point that people’s blind assumption that the best fossil records were always gradual was just wrong. It is clear that they do show discontinuities.

‘However, there’s a two-part difficulty with the argument. The first is that what is a jerk to a palaeontologist like Gould is a creep to a biologist. So there’s a mind-set difference. And second, even the most traditional of Darwinists don’t deny the fact that some things stay the same for a long time, especially where the environment stays the same.’

Despite overwhelming evidence for the truth of Darwinism, opinion surveys in the United States consistently show that less than 50 per cent of people think that human beings are evolved animals. What does Jones think of the situation in the States? Is it a cause for serious concern?

‘There is a kind of new ignorance out there which is depressing,’ he replies. ‘There is a deep intellectual dishonesty about creationism which I really despise. There is dishonesty in that they lie to themselves. But what’s more important is that they’re lying to a new generation of children. They’re using a false claim of intellectual honesty to spread intellectual dishonesty.

‘You don’t start every geography lesson with a proof of the fact that the Earth is round; we’ve gone beyond that. And we should have gone beyond having to prove Darwinism every time we talk about evolution. But in the US, a lot of biologists in universities have to spend a large part of their time putting the kids right about the fundamental facts of biology, things which they should have been taught at school, but weren’t.

‘Although philosophy is largely useless, I think there is some interesting philosophy of science. I’ve always liked Karl Popper’s view that science is about disproving things. If we find Neanderthal man wearing a Rolex watch, then I’m going to give up the theory of evolution. But so far that evidence has not appeared. Or take the fact that the Sun is at the centre of the Solar System. If astronomers were suddenly to find that the Sun went around the Earth, they might moan and groan, but they would admit that they were wrong. They’ve done this before, in 1905, with Einstein’s theory of relativity; they threw everything out of the window, and effectively started again. But creationists don’t think like this. They think that unless it is possible to prove Darwinism beyond all doubt, then it isn’t true. But ironically, of course, what they’ve committed to themselves is both entirely beyond proof and also unfalsifiable.

‘It’s also interesting that if you look at the literature on evolution, it is full of disagreement. Indeed, there is a lot of bitter disagreement: creeps and jerks, as we discussed, for example. Biologists spend their time quarrelling. If you go to a church, you just don’t see the same kind of disagreement. They all think God is marvellous, and that Jesus was a great bloke. So, if you’re very naïve, it sounds as if the creationists have a stronger case than we do, when, of course, the opposite is the case.’

It isn’t only creationists who are made nervous by talk of Darwinism and genes. Many people working in the humanities and social sciences, for example, are suspicious of theories which appeal to innate factors in order to explain particular behaviours or particular characteristics of the social world. This becomes especially controversial when it involves the comparison of different groups of people with each other. The classic example of this is the in-fighting which has surrounded those studies which have compared the IQ levels of different racial groups, and which have found that there are systematic differences. What does Jones make of this kind of work? Does it have scientific merit?

‘This has always been a messy issue, because obviously there are political implications,’ he answers. ‘This sort of research has been used, post-Galton, for various things which we don’t even want to think about. But nevertheless, there is a scientific issue here which is worth considering. It isn’t out of the question that one population group is smarter than another for genetic reasons.

‘There has been a lot of debate in the United States recently about the use of racial categories in medicine. In the literature, there has been much discussion about whether black people respond better than other groups to particular drugs or treatments. A recent paper looked at all the studies. The first thing that was found was that skin colour is a proxy for poverty. This is so obvious that people tend to forget it. But if you take it away, whilst the difference between racial groups narrows, it is still there. In particular, there’s a heart medicine which apparently works better for blacks than it does for other people. And this sparked a controversy. When it was first suggested, three or four years ago, a whole load of angry lefties wrote to say that people shouldn’t say this kind of thing. But this is silly; if there are differences, then we need to know.

‘But what was really interesting was that when a group here looked at differences around the world, they found that whilst there were indeed differences in how population groups responded to particular drugs, these differences did not coincide with traditional racial classifications. For example, West Africans don’t respond in the same way as East Africans. So the traditional racial groups, which appear to the naked eye to be distinct, perhaps rather surprisingly are not.’

‘Even so,’ Jones continues, ‘it is still possible that there are genetic differences between groups which have an effect on IQ scores. But actually the data does not support this conclusion. Let’s assume that the heritability of IQ is 0.6; that is, that the proportion of total variation in IQ due to genetic variation is 0.6. Let’s accept, though I wouldn’t, that there is a difference of 15 points between the IQs of black and white Americans. It might seem to follow that given that most of the variation in IQ is due to inherited factors that this difference between black and white scores must be due to genetic factors. But this is a fundamental misunderstanding of the meaning of the word heritability.

‘The way I often illustrate this is to talk about blood pressure. If you measure the blood pressure of middle-aged black men in the US, you find that, on average, they have a higher blood pressure than white men. This causes quite a lot of mortality. If you look at the heritability of blood pressure it’s around 0.4. So doctors then say, “Oh dear, it’s the lifestyles of black people, they smoke too much, they don’t do enough exercise, their environment must be pushing up their blood pressure. We should do something about this.” But, on the basis of exactly the same data, educationalists say, “Oh, it must be genetic, there is no point in doing anything about it.” But, of course, they’re both wrong. We know that there is some genetic predisposition among some Africans towards high blood pressure; they have high levels of salt in their blood, which pushes up their blood pressure. But there are also environmental factors–too many cheeseburgers, for example–which increase their blood pressure.

‘So the data simply doesn’t support the case that any difference in the IQ levels of different racial groups is a function of genetic differences. Geneticists have made this point over and over again, but still some people refuse to accept it.’

Perhaps the aspect of the science of genetics which worries people most in the UK has to do with genetically modified crops. However, this worry does not seem to be shared by most scientists. Ed Wilson, for example, argues that whilst there are legitimate concerns about GMOs, the potential benefits outweigh the risks, so we should continue to use the technology. What’s Jones’s view about this?

‘Actually, I think that the whole GM debate in the UK has been lamentable,’ he replies. ‘First of all, there was the blithe assumption on the part of scientists that they could go ahead without consulting the public. This, of course, just shouldn’t be true; I don’t think any serious scientist would ever claim that it ought to be true.

‘The Greens for their part have just been totally dishonest about the whole thing. A little while ago, I was booed by 3,000 people at Central Hall in Westminster, after I asked which political party had been the greenest in Europe; there’s no doubt about the answer, it was the Nazis. They were completely green. They were interested in the purity of blood. They didn’t like smoking. They wanted forests. They were all for exercise. They didn’t like cars. A lot of this anti-GM food stuff has a strange atavistic purity of blood thing going on. I don’t want to overstate it, but it is definitely there.

‘The Greens have been absolutely cynical in manipulating public concern about GM foods. It’s the dishonesty of their approach which annoys me. If they don’t like industrial agriculture or the common food policy, then I’m in agreement with them. But to muddy the water with completely spurious arguments about GM food and human health, for example, is a disgrace.’

So does Jones then share Ed Wilson’s view that it is the potential for increased crop yields...