A few weeks back I mentioned Randy Nesse in the context of his aside about ageing. Long story short, I was so impressed by this guy’s discussion that I bought his book Good Reasons for Bad Feelings. His angle is to look at how evolution accounts for the most complex aspects of human biology. I’m loving it. His focus is looking for evolutionary reasons for psychological conditions. You might think that would be nothing new, though he points out that it was something very new when he picked up his interest in it half a century ago. Surprisingly, it still is a relatively uncommon way of looking at psychological disorders. And thirdly people often misunderstand the mechanism in ways I will refer to. 

Something I admire – try to aspire to myself and routinely find tough – is finding simple metaphors to illustrate complex things in a clear way. And I would give Nesse at least eight out ten for this. What he is dealing with is fearsomely complicated, and he comes up with some beautiful metaphors, perhaps the smoke alarm is his best one. However complexity still rises like the morning mist to blur the light of dawn (see what I did there?) Anyway – the discussions make so many turns that it’s still fairly easy to get tangled up. 

So I’ll cover the smoke alarm illustration since I have mentioned it. He’s talking here about anxiety. Anxiety is universally seen as a problem, but he points out that people without anxiety die young – and maybe back in the day that might have meant too young to reproduce, so it’s a good trait to have at least a bit of. Then he points out that smoke detectors sometimes give false alarms. They give false alarms more often than they fail to operate when there is a fire. If they never gave false positives then the range at which they are sensitive would have to be set artificially high on the risk spectrum. That might, or probably would, allow more fires to start without setting off the siren at all. Thinking about it, a false positive alarm is a minor annoyance, a false negative (ie a failure to sound the alarm at all) can be a disaster. 

Now,  think of your ancestor at the water hole. If she was anxious and thought that the rabbit in a shrub was a tiger, she might have wasted a few calories running away. But if she is so laid back that she assumes the tiger is a rabbit or even a really cool stripey cat, then she becomes lunch. That your ancestor survived means she was, let’s say, anxious enough, and quite likely a bit too anxious, but not far too anxious, otherwise she’d have died of thirst. Viewed in this way we should be grateful that evolution has gifted us the ability to be anxious, and hardly be surprised if it has left us with more false alarms than we would like.

Apart from giving us a neat academic explanation for one of the ways stuff might be as it is, he points out that it can be surprisingly therapeutic for someone suffering from chronic anxiety to be able to see their own situation as a poorly adjusted but necessary alarm mechanism rather than (wholly) as a pointless damaging disease. 

So, what about the ancestor who would have died of thirst if her anxiety was tuned so high as to make her nothing but a bag of nerves? Well there will always be outliers on the bell curve in the generations that evolved since waterhole days, and secondly in the modern era or actually at any time when there were social groups, maybe someone else would bring the water. And so it remains that the evolution of anxiety has every incentive to raise alarms at least as often as necessary, and it doesn’t have much incentive to care about being cool.

Another way he illustrates that anxiety may be a positive is by examining why women live longer than men. He suggests that women don’t actually live longer, it’s just that men tend to die young. He has written a paper about this which mentions ‘Being male is now the single largest demographic risk factor for early mortality in developed countries.’ Old men, he explains, don’t actually peg out much before old women. What happens is that silly young men accidentally kill themselves because they don’t have enough anxiety, and this brings the average down. (Women in these terms have about the right amount of anxiety.)

Now, sex and drugs and rock and roll are all most exciting for men at the same age as violence and extreme sports, so by the time our hero tops himself by jumping off a cliff in a batsuit, he has probably already done more than enough mating to propagate his lack of anxiety. 

I tried to check this thesis out by downloading life expectancy tables from the UK Office for National Statistics and they didn’t seem to confirm it. I graphed life expectancy as a percentage differential between male and female by age. Having taken account of Nesse’s statement, I expected the lines to start widely separated and then to sweep together just after the age when men stop being recruited to the armed forces. After that I thought that the small remaining  differential would perhaps taper away to zero just before the few remaining centenarians died. 

The difference doesn’t seem to behave like that though. Maybe there are other factors, maybe men don’t stop being life-threateningly silly until they are in middle age, or maybe my understanding of statistics is rubbish. As observed by Mark Twain in a famous statement generously attributed by him to Benjamin Disraeli – The study of statistics is a notoriously difficult area of basic maths to interpret correctly. If anyone would like to clarify this is a comment to me I’d be really grateful. I should mention that anxiety or the lack of it is not the only reason for early male mortality mentioned in Nesse’s paper. Maybe if I can’t work it out myself I’ll submit a query to my favourite statistician Tim Harford and report back here if I get a response.

Meanwhile three of Nesse’s recurrent threads are, 

• Avoiding what he calls VSAD or viewing symptoms as diseases.
• Avoiding the temptation to search for what gene causes what disorder. Better ask what environmental situation may have led to the evolution of a pattern of behaviours that increases evolutionary ‘fitness’ – inevitably by the incalculable interaction of multiple genes influencing emotions and hence behaviour.
• And his third recurrent thread is speculating on how what may have been a good evolutionary response has evolved into what are some of today’s most debilitating disorders. 

I have already given an example of the third one, so what about the other two?

That first one about viewing symptoms as if they are diseases provides a nice illustration of how he clarifies stuff, but it still remains fearsomely complicated. I don’t blame Nesse for this. If he oversimplified the subject with the risk of misinterpretation, that would be much worse. 

So on the subject of VSAD, he points out that psychological difficulties are widely considered to be diseases or disorders, but say coughing, or pain, or running a temperature are considered as symptoms. It’s easy to understand that physical symptoms have benefits. Pain helps keep you out of danger, coughing expels the mucus that your body makes to trap bugs, and fevers provide a better environment for your immune system to work fast. Once we realise that mental pain has a function similar to physical pain then it’s possible to consider where it came from and how to deal with it, maybe even whether to deal with it. 

But it’s still complicated. In physical medicine for example, there aren’t just symptoms and diseases, there are whole syndromes or collections of chronic symptoms again which don’t map neatly one to one against diseases. This muddies the water. And so it is with mental problems. The water here is already muddy, so it’s not an easy thing to clarify.

On the second line, that one about mapping mental problems to genes. He shows how a great deal of work has proven fruitless, and it shouldn’t come as a surprise. There is no gene for something as measurable as height, why should there be one for something that we can’t even classify? It would be like looking for a gene for coughing. 

So the questions he asks are more along the lines of ‘what response would have helped evolutionary fitness in what circumstances?’ How do those circumstances map risk? Given that we aren’t automata, there are plenty of physical behaviours that aren’t hard-wired, so our emotions and moods act as a kind of middleman in making us feel like doing something, and that something will always be what benefits the transmission of relevant genes. 

In passing, I should mention that the mechanism of evolution doesn’t care if we suffer from pain or depression or anxiety, it cares about whether we survive long enough and behave in the right way to pass the characteristic on to the next generation. Often our genes require us to suffer pain for our own survival. No. Sometimes not even for our survival, just for our survival long enough to pass on the characteristic. The benefit to what Richard Dawkin called the Selfish Gene in his book of that name always trumps my comfort or your wellbeing.

On a positive tack Nesse considers fruit gathering and the question of when to leave one shrub and look for another, and then when to stop gathering for the day and go home. He shows that we instinctively know this stuff and the mechanism is that we will naturally lose interest in a fruit bush before it is completely empty. We will actually move on when the scarcity of fruit means we waste more time in searching for the last ones on it, than we would spend in looking for a new bush. So he establishes that instinctive mood affects behaviour in a way to maximise efficiency, and for once our interests align with those of our genes. We both just want a good fruit salad. 

Then he talks about how having the ability for a wide variety of moods might benefit a species in times of scarcity, in times of plenty and in times when scarcity and plenty fluctuate predictably and unpredictably. Now these things aren’t easy to calculate, but they are comparatively easy to model. And sure enough that’s exactly what evolution does; it throws some mud at the wall and sees what sticks. 

How has evolution moulded our emotions and feelings and moods? Maybe responses that helped survival would have been passed down in one gene, or in a combination of the physical or behavioural forms that were produced by numerous genes. And sure enough it’s pretty much always the latter. Genetic evolution has to be gradual to avoid throwing the baby out with the bathwater. It takes many generations, so it has the capacity to deal with combinations and subtlety that would be impossible to calculate by pen and paper.

I like this way he moves forward in this discussion. In fact I wish he were a bit more logical in building his structure of the argument. I rather feel as if I’m sitting in front of a bonfire watching sparks of initiative arise from a hotbed of wisdom. I love seeing what he has to say but I yearn for all that to be put into even more of a logical structure. I’m only half way through the book at the moment; perhaps it will be.

Depression isn’t as simple a thing to account for as anxiety. Nesse softens our expectations a bit by pointing out that clinical diagnosis of depression has fluctuated wildly over the past half century – between whether or not to take account of temporary situations and/or life experience for example – however he settles on a kind of definition where depression is like chronic low mood and he speculates about how that could be useful and how and why it can be unbalanced.

He points out first how an infant will cry for its mother immediately after separation, but then will become quiet and withdrawn, and speculates that this is good survival instinct to conserve resources and not attract predators. But that’s not really a good enough foundation for a whole messy branch of psychiatry as the smoke alarm was for anxiety. So his discussion gets more complicated and certainly too complicated for me to summarise here, but always beautifully and sympathetically discussed.

Nesse constantly reminds us that what’s good for the propagation of a genotype may actually hurt the living animal – that’s you and me, and it certainly hurt our mothers at the moment of our birth. And so again and again Richard Dawkins pops into my mind. I have to admit that I find that guy unbelievably smug and hence rather annoying, and brilliant. It’s a great thing to look at complex stuff from a totally new angle and The Selfish Gene changed our perspective on evolution as surely as Copernicus changed our perspective on the solar system.

The concept that animals are what genes are for is so intuitively obvious that even the name of the book is often misunderstood to mean that animals are selfish because they need to be to pass on their genes. But it’s the other way around. The Genes are selfish and we animals are just the carriers. That’s all that our physical characteristics and our behaviours do.  What I love about Nesse is how well he explores how those selfish genes use our psychology to pull our behavioural strings. And the other thing I love about Nesse is that he doesn’t come across as smug, just wise. It makes his work so much nicer to read!