In science, no work is completed until it has been picked to pieces

Dangerous dithering.

What does a scientist have to do to convince you? The answer used to be “wait until his critics die” – hence the physicist Max Planck’s assertion that science advances one funeral at a time.

But sometimes even that is not enough. Late last month, the smell researcher Luca Turin published striking new evidence supporting an idea first put forward by Sir Malcolm Dyson in 1938. Dyson presented his “vibrational” theory of how our sense of smell works to universal apathy. Three generations later, scientists are still saying “meh”.

That year, 1938, was also when it was first argued that pumping carbon dioxide into the atmosphere would raise global temperatures. The idea came from the steam engineer Guy Stewart Callendar; the broad response was “implausible”. Today, in 2013, scientists have shifted: they generally agree that Callendar was right. Yet there remains a dangerous level of disagreement about the detail.

At least Turin’s scientific peers have presented him with a clear path to follow. Dyson’s idea was that when a molecule gets up our nose, its characteristic smell is created by the way the bonds within that molecule vibrate. In a clever piece of experimental work, Turin has shown that human beings can distinguish between two molecules that differ only in the way they vibrate. The two molecules tested were both cyclopentadecanone, but while one contained normal hydrogen atoms the other contained “deuterated” hydrogen, which has an added neutron in its atomic nucleus. The additional particle creates a difference in the way the molecules vibrate. And that is why, according to Turin, they smell different to us.

The experiment punches a hole in the accepted theory of smell, which says that smell experiences are triggered by differently shaped molecules fitting different receptors in the nose. This “lock and key” idea can’t explain why two identically shaped molecules smell different. But Turin’s critics said last month that before they will even consider accepting his theory, they want him to show exactly what goes on in human smell receptors.

They are right to make such demands. This is science, where no work is finished until it has been picked to pieces. But that is exactly why it has been so easy to do so little about climate change since 1938. Later this year, the Intergovernmental Panel on Climate Change will make some highly equivocal, backtracking announcements. In a report due for release in December, the IPCC will concede that we can’t be sure tropical cyclones will become more frequent, or that droughts will get worse. Worries that the Gulf Stream will collapse, tentatively raised in the 2007 IPCC report, are allayed: such an event is “unlikely” to occur in the foreseeable future.

Concern over details can have an unhelpful effect, masking the big picture on climate change – the one that Nicholas Stern, who wrote the UK government’s 2006 review on the science, said at Davos last month is “far, far worse” than we were led to believe originally. Until that, rather than the detail, becomes the focus, we can continue to dither over whether to do anything, let alone deciding what course we might take.

It does not matter a great deal that no one is willing to risk his career by backing Luca Turin – but to wait for absolute certainty over the details of climate change before we do anything about it will spell life or death for many. If science continues to advance one funeral at a time, its acceleration is assured; and there will be no shortage of funerals in a world that’s 4° warmer.

Michael Brooks holds a PhD in quantum physics. He writes a weekly science column for the New Statesman, and his most recent book is At the Edge of Uncertainty: 11 Discoveries Taking Science by Surprise.

This article first appeared in the 11 February 2013 issue of the New Statesman, Assange Alone

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Scientists have finally said it: alcohol causes cancer

Enough of "linked" and "attributable": a new paper concludes that alcohol directly causes seven types of cancer.

I don't blame you if you switch off completely at the words "causes cancer". If you pay attention to certain publications, everything from sunbeds, to fish, to not getting enough sun, can all cause cancer. But this time, it's worth listening.

The journal Addiction has published a paper that makes a simple, yet startling, claim: 

"Evidence can support the judgement that alcohol causes cancer of the oropharynx [part of the throat], larynx, oesophagus, liver, colon, rectum and [female] breast"

So what's especially significant about this? 

First, scientists, unlike journalists, are very wary of the word "causes". It's hard to ever prove that one action directly led to another, rather than that both happened to occur within the same scenario. And yet Jennie Connor, author of the paper and professor in the Preventive and Social Medicine department at the University of Otago, New Zealand, has taken the leap.

Second, alcohol not only causes cancer of one kind – the evidence supports the claim that it causes cancer at seven different sites in our bodies. There was weaker evidence that it may also cause skin, prostate and pancreatic cancer, while the link between mouth cancers and alcohol consumption was the strongest. 

What did we know about alcohol and cancer before?

Many, many studies have "linked" cancer to alcohol, or argued that some cases may be "attributable" to alcohol consumption. 

This paper loooks back over a decade's worth of research into alcohol and cancer, and Connor concludes that all this evidence, taken together, proves that alcohol "increases the incidence of [cancer] in the population".

However, as Connor notes in her paper, "alcohol’s causal role is perceived to be more complex than tobacco's", partly because we still don't know exactly how alcohol causes cancer at these sites. Yet she argues that the evidence alone is enough to prove the cause, even if we don't know exactly how the "biologial mechanisms" work. 

Does this mean that drinking = cancer, then?

No. A causal link doesn't mean one thing always leads to the other. Also, cancer in these seven sites was shown to have what's called a "dose-response" relationship, which means the more you drink, the more you increase your chances of cancer.

On the bright side, scientists have also found that if you stop drinking altogether, you can reduce your chances back down again.

Are moderate drinkers off the hook?

Nope. Rather devastatingly, Connor notes that moderate drinkers bear a "considerable" portion of the cancer risk, and that targeting only heavy drinkers with alcohol risk reduction campaigns would have "limited" impact. 

What does this mean for public health? 

This is the tricky bit. In the paper, Connor points out that, given what we know about lung cancer and tobacco, the general advice is simply not to smoke. Now, a strong link proven over years of research may suggest the same about drinking, an activity society views as a bit risky but generally harmless.

Yet in 2012, it's estimated that alcohol-attributable cancers killed half a million people, which made up 5.8 per cent of cancer deaths worldwide. As we better understand the links between the two, it's possible that this proportion may turn out to be a lot higher. 

As she was doing the research, Connor commented:

"We've grown up with thinking cancer is very mysterious, we don't know what causes it and it's frightening, so to think that something as ordinary as drinking is associated with cancer I think is quite difficult."

What do we do now?

Drink less. The one semi-silver lining in the study is that the quantity of alcohol you consume has a real bearing on your risk of developing these cancers. 

On a wider scale, it looks like we need to recalibrate society's perspective on drinking. Drug campaigners have long pointed out that alcohol, while legal, is one of the most toxic and harmful drugs available  an argument that this study will bolster.

In January, England's chief medical officer Sally Davies introduced some of the strictest guidelines on alcohol consumption in the world, and later shocked a parliamentary hearing by saying that drinking could cause breast cancer.

"I would like people to take their choice knowing the issues," she told the hearing, "And do as I do when I reach for my glass of wine and think... do I want to raise my risk of breast cancer?"

Now, it's beginning to look like she was ahead of the curve. 

Barbara Speed is a technology and digital culture writer at the New Statesman and a staff writer at CityMetric.