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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Personal experiences – not just biology – shape who you find attractive

Researchers find past experiences play a role in identifying why people are attracted to certain individuals.

A new study suggests personal experiences influence our attraction to our preferred partners. It was previously thought genes played a bigger role, as they do in forming other examples of behaviour and character traits. Just reflect on the number of times you've been singled out by a family member for acting like one of your parents, either offensively or in a praiseworthy way.

There are certain characteristics that lead people to judge particular faces as more attractive than others, such as the level of symmetry. However, people still dispute others' opinions when judging facial attractiveness – it's subjective. After all, what else is the purpose of the romantic lead's sassy best friend in any rom-com or book? Or just think how boring conversations with your friends would be without such intense and passionate disagreements.

The researchers used twins as participants in the study in order to monitor these differences and disagreements in opinion. This was necessary because twins are, by definition, genetically identical, allowing the scientists to rule out genetic differences as a reason in explaining their findings.

A total of 547 sets of identical twins and 214 sets of fraternal twins (siblings sharing half of their DNA) were asked to judge the facial attractiveness of 102 female faces and 98 male faces, and give each face a rating based on preference. The results showed, on average, the twins agreed with each other 48 per cent of the time, and disagreed on facial attractiveness 52 per cent. Had the numbers been closer for both the identical and fraternal groups, this would have shown genes were more influential in determining our levels of attraction to others.

The study concluded the reason behind this difference was primarily based on an individual's unique environmental factors (the scientific phrase for "past experiences"), at 78 per cent.

Previous studies have shown aesthetic preferences are based on a range of other factors too, including socioeconomic and cultural features, the rater's own facial features and also personality. (See, it's not always about looks.) The authors were also able to determine how our genes influence facial recognition during this same experiment, if not our preferences.

Discovering that a personality characteristic is influenced by our environment is another highlight in the field of behavioural genetics, as it was previously thought "nature beats nurture" in many aspects of an individual's behaviour. However, this study shows that a person's experiences are unique even between family members.