Evolutionary insights for public policy

The significance of an evolutionary approach to public health is increasingly being recognised. The negative effects of poverty and inequality are also being recognised as a huge burden on health. Occasionally, the two are even combined to acknowledge our evolved responses to inequality.

Overall though the various efforts seem to have stopped short of explicitly proposing an evolutionary explanation to the Spirit Level evidence between countries. Understandably, the focus has been on measures like teenage pregnancy and breastfeeding rates that directly measure life history (LH) strategy (see this post on LH theory). But other outcomes may be the result of a faster LH strategy too: infant mortality may be higher in more unequal countries because of a reduced biological investment in each child, leading to low birthweight and prematurity.

The other outcomes in the Spirit Level can be brought under the life history strategy umbrella too, with its general principle of short-termism. The harsher and more unequal the social environment, the more uncertainty there is over long-term prospects. This would have been true in our ancestral environment too, and with morbidity and mortality rates so much higher, the selection pressure on behavioural strategies would have been extremely strong. The danger of dying before or during reproductive years made early reproduction paramount. As a result, we evolved a comprehensive response to harshness, which speeds up the course and development of key life stages, and prioritises reproduction over growth.

The response is evident in various domains:

Biologically, periods of growth are shortened, and puberty is brought forward. As in Barker’s thrifty phenotype hypothesis, where less important organs like the pancreas get less energetic investment when energy is scarce, physical size is sacrificed to allow reproduction to occur earlier. This under-investment early on in life may lead to the various health problems that develop later. Of course middle-aged health problems wouldn’t have been a major problem evolutionarily, if the early reproduction meant that your genes had been passed on in a difficult environment. They may not even have developed, with an environment of low calorie availability and an active lifestyle avoiding the metabolic disorders seen today. The molecular symptom of quicker development is oxidative stress, which is a measure of the biological stress on an individual. It is linked with chronic low-level inflammation and suppression of the immune system. Heightened cortisol levels, and activation of the hypothalamic-pituitary-adrenal axis which releases adrenaline, are also implicated. The response to stress is complex, but the various measures are consistently related to low socioeconomic status, and so can be argued to be part of the fast LH strategy.

Cognitively, people show a higher rate of a cognitive bias known as future discounting. This involves taking smaller, short-term gains at the expense of larger, long-term ones. Delaying gratification and impulse control require a low rate of future discounting.

Behaviourally, this bias could be argued to underlie almost any of the behavioural problems in the Spirit Level – drop-out rates from high school and low educational attainment, unsustainable environmental practices, addiction of any kind, from gambling to alcohol and drugs. Public goods problems (like climate change) require a long-term assessment of costs and benefits, so a bias to discount the future is disastrous for agreements on action. Hierarchy also encourages conspicuous consumption to signal status – another unsustainable practice. Future discounting may explain why trust is lower in more unequal countries, as a long-term view is needed to help someone today, when you may not be paid back for a while.

Parental investment is another feature which is sacrificed in the fast LH strategy. This is seen in harsher parenting styles. Parental inconsistency has been linked with elevated levels of stress hormones in children. And one of the parents may not even be there – 26% of families in 2011 were single-parent households. Absent fathers account for the vast majority of these. The effect on boys is the development of excessively masculine traits; girls hit puberty earlier. Both genders are more likely than average to repeat their parent’s lifestyle. The UNICEF index of child wellbeing correlates negatively with inequality, as do childhood behavioural problems.

Consequently, mental health suffers in unequal societies – especially anxiety. This can’t be said to be adaptive in modern society, but as with chronic stress, it is possible to theorise how it could have helped in an ancestral environment. In small doses, anxiety and low mood may have been one way of avoiding conflict, by avoiding aggression from others. But as with stress, constant exposure is pathological.

Inequality, by stratifying the social hierarchy, favours competition over cooperation as the way we interact with each other. Status becomes more important, as it has always signalled an ability to access resources, including mates. Excessive inequality means that those at the top can monopolise resources, and those at the bottom have nothing to lose when they try to climb the ladder. This manifests itself in higher rates of violence and homicide. Men may go to greater lengths to keep partners as well as compete for them, using violence and sexual coercion. The violence statistics don’t include sexual violence due to international differences in definitions, but (not unrelatedly) the status of women and gender equality are better in more equal countries.

In order to bring about the policy changes necessary to reduce inequality, disparate interest groups need to be made aware of the wide-ranging effects of inequality and the associated LH traits, in order to campaign with a louder voice together. This means physical and mental health organisations, alcohol and drugs charities, violence reduction schemes and so on could benefit from coming together to work for something that would tackle all of their respective issues at source. It’s not about creating a ‘natural’ environment – there’s no such thing, as we adapt to vastly different societies. It’s recognising that a more equal society brings out the best of our nature.


Discounting an Independent Scotland

In one year, Scotland will vote on whether to become an independent country. The campaigns for both the Yes and No votes are getting into full swing. Crucial to reaching the right target audience is understanding the profile of voters for each side. Studies like the Scottish Social Attitudes Survey allow people’s voting preferences to be analysed alongside a wealth of other information about them, to see if any trends emerge.

What Scotland thinks

So which sections of the population are more likely to vote Yes? First up, there’s a well-established trend for younger people to be more likely to support independence. Critics argue that the SNP are exploiting this by lowering the voting age from 18 to 16. Another finding from various polls is ‘the Braveheart effect’ –  men are more likely to support independence than women. And those in working class occupations are more likely to support independence than their middle class compatriots.

It’s easy to construct reasons why each group of people might be more inclined to vote Yes. But could there be a common, underlying factor that unites these seemingly disparate groups? One theory states that it is the consequences of independence that are foremost in people’s minds – a hard-headed analysis of the likely economic changes under independence, rather than an ideological attachment to either independence or the union. A telling survey question ‘would you vote for independence if you would be £500 per year better off?’ finds that a majority would do so.

Delayed gratification

Such a commercial offer is reminiscent of a psychology experiment that explores how people think about the future. It asks a series of questions on whether you would prefer to get, for example:

£10 today


£20 in a month’s time.

Preferences vary widely from strongly preferring the immediate reward, to always holding out for the bigger payout. In the jargon, the trait is known as future discounting: if you take the money and run, you have a steep discounting rate, whereas if you delay your gratification, you have a shallow discounting rate. The idea is that the more you think about the long term, the further away are your time horizons and the more importance you assign to future outcomes. Conversely, if you are more present-oriented, you discount the future and value present resources more highly.

To the extent that future discounting can be applied to the independence debate, it might be used to assess the accusations on both sides of not thinking through the long-term consequences of a Yes or No vote. The evidence on future discounting suggests a controversial conclusion – those groups more likely to vote for independence are the same groups that discount the future more steeply.

Living for today

Men on average prefer immediate rewards to a greater extent than women. This has been linked to sex differences in competitive behaviour, and the general tendency for men to be more likely to ‘live fast and die young’. Similarly, younger people show more short-term thinking in future discounting experiments. One study found the opposite, however. But evidence on impulsivity seems to suggest that younger people favour immediate returns while disregarding the consequences – the majority of crimes are committed by young males.

Those in lower socioeconomic status (SES) groups also show a steep rate of future discounting. Groups with more education or a professional occupation have a more future-oriented time perspective. Another study found that people who grew up in poverty react to mortality risk by valuing the present and discounting the future more.

All of the above doesn’t necessarily mean that those people who say they’ll vote yes have steeper future discounting rates. It would be extremely easy to test this though, simply by inserting a future discounting test on one of the numerous surveys on independence. And even if this returned a positive result, it doesn’t mean that their decision to vote yes is a result of their steeper rate of future discounting. If it is though, it could be a rational response to having less to lose and more to gain in a shake-up of the economy, as younger people and those in lower SES groups do.

The interest of all this to the Yes and No camps would be little more than academic, if it simply spells out who will vote for each side next September. But if it could be used to influence people’s voting preference…

Nudge, nudge

Recent research in the field has gone from looking at how individuals differ in their preference, to actually trying to change it. This usually takes the form of showing relevant cues to participants, and seeing what effect this has on their discount preference.

For instance, even just being shown pictures of poverty leads to favouring the immediate reward in a classic discounting experiment. Our adaptive response to a lack of resources is also triggered by physical shortage – having a low-calorie drink with artificial sweeteners primes us to take the ‘smaller but sooner’ reward. In contrast, having a sugary drink actually decreases our rate of future discounting. The more food there seems to be in the environment, the more we can plan for the long term without worrying where our next meal is coming from. Men are susceptible to another cue – pictures of attractive women.

Independence polling itself has found evidence of an analogous ‘priming’ effect. Asking Scots first whether they think that the Scottish Parliament does a good job (which the majority do), and then asking whether they support independence, increases the proportion who say yes.

From theory to practice

So could the insights on future discounting be used to prime people to be more likely to vote for one side? Again, a study could use established cues to induce a discounting bias, and then ask participants for their opinion on independence. The campaigns would be advised to make use of appropriate cues to elicit their desired bias. This would create an implicit meaning in campaign materials and communications that reinforces their explicit message.

A tendency to discount the future may be the common factor that unites the sections of the population who are more inclined to vote Yes. But to the extent that future discounting is malleable, attitudes towards independence could be influenced. Given that more than one million voters are undecided, the opportunity is there.

Inequality and life history theory

Societal problems cluster together. This was true when squalor, want, idleness, disease and ignorance were Beveridge’s five great evils, and it is true now when an index of multiple deprivation is used to measure social disadvantage, and health co-morbidities are a dominant issue. That these problems are concentrated in one section of society is taken as read – how could it be any other way? But compare different rich countries on their average performance, and some consistently outperform others on a wide range of outcomes. Wealth can’t explain this as the countries are all at the top table. Inequality is coming to be recognised as the cardinal factor.

While the stats don’t lie on this, they beg the question why inequality has so many nefarious consequences. To explain problem behaviours, a theory of how the social environment affects people psychologically is needed. The explanations that are put forward are usually at the proximate level – psychosocial effects for instance. These explanations are entirely valid, providing potential causes of poorer health and wellbeing. The ‘why’ question can always be asked again, though: why does inequality have such a negative psychosocial effect on us? Answering this question involves moving to the grandly titled ‘ultimate’ level of explanation – the adaptive value of behaviours.

This is a big change in the context of explaining problematic behaviours like violence and teenage pregnancy, which are understandably usually seen as maladaptive responses. But variation in such traits can be seen as adaptive, according to life history (LH) theory. While the idea is lodged in evolutionary psychology, it has little interest in genes or innate predispositions, though acknowledging they exist. Rather the emphasis is on how we adapt our behaviour to the living environment we find ourselves in.

LH theory originally dealt only with differences between species. It sought to explain why some species mature quickly, produce large numbers of offspring, and invest little parental care in them, and other species follow the opposite pattern. These LH strategies are seen as being on a fast-slow continuum, with different species occupying different places on it. Energy can be invested in growth or reproduction – fast LH traits make the most of current resources to prioritise reproduction. This makes sense in an environment where survival is uncertain – i.e. if individuals of a species can’t be sure that they’ll live through their reproductive years, strategically they should reproduce earlier to ensure their genes are passed on. If they followed a slow strategy, they would risk dying before reproducing.

Humans occupy the extreme slow end of the LH continuum. We take decades to mature and reproduce, and invest heavily in caring for a small number of offspring. But there is individual variation. LH theory can been applied to these differences using the same logic as what influences between-species differences – how amenable the environment is to investing in long-term growth. Mortality is much lower now than in our evolutionary past. Disease, famine, lethal violence, death in childbirth and infant mortality made survival difficult until very recently in our evolution. Although these threats are greatly reduced, cues of these threats to survival, or environmental stress, will still be salient psychologically. These cues may not accurately predict threats in modern society, leading to a mismatch between what we’ve evolved to react to and what is important to survival today.

The ideal environment to grow up in is one where access to resources is assured. It is clear that people in developing countries follow a faster LH strategy – this underlies the demographic transition of women having fewer children as a country gets richer. And in developed countries, those lower down on the income distribution follow a fast LH strategy. Social status is key. Primates are hierarchical, and high-ranking individuals can monopolise resources. This is one reason why not only material deprivation, but relative deprivation is so nefarious psychologically. In addition, more unequal societies have more stratified hierarchies, which exacerbates the social cost of being at the bottom. And even those further up the ladder seem to be affected by excess inequality.

It looks like even among rich countries, the more unequal countries engender a faster average LH strategy. This wouldn’t be a big surprise, as those problems which are worse in more unequal countries are also those which show a strong social gradient. It is well established that more unequal countries do have more of these problems – LH strategies could be driving this. This suggests that inequality is a salient cue for environmental harshness.

The fast LH strategy is based on the uncertainty of long-term resources. Someone learning that they can’t rely on long-term access to resources develops a cognitive bias towards discounting the future. This means that when offered a certain amount of money today or a larger amount in a week’s time, they prefer the immediate reward. It encourages short-termism, and discourages investing in the future. The fast LH strategy’s associated behaviours are all based on discounting the future, and making the most of current resources.

They are also all seen as social problems: teenage pregnancy, unhealthy eating, alcohol abuse. Future discounting leads to risky behaviours like driving dangerously, and risky sexual behaviour. Education campaigns are often used to try to reduce problem behaviours. Their effectiveness may be limited as they appeal to people directly, whereas LH theory suggests that subconscious influences are the main driver of variation in behaviour.

A LH theory informed approach would seek to get to the root cause of problem behaviours. Inequality is chief amongst them, with a large body of evidence behind it. There are other, more specific factors which act as cues of environmental harshness, and so speed up LH strategies. Father absence leads to girls developing and maturing more quickly, and increases masculine traits in boys. Urban decay, lack of social support and the stream of tragic news stories of people dying young must all have an effect.

As if all of the above wasn’t enough, the fast LH strategy is bad for the environment. Immediate consumption of available resources is what has led to global warming and climate change. And by discounting the future more steeply, people on the fast LH strategy may even be less able or willing to see the long-term consequences of their actions. More equal countries recycle more, and have proved more willing to act on climate change.

Because the range of problems that LH strategies influence is so wide, slowing down average LH strategies would bring multiple benefits to society. This  could even be achieved without additional expenditure, simply by redistribution to reduce inequality.

Did Labour’s amendment scupper the Government’s Syria vote?

Before the crucial vote on military action in Syria on Thursday night, an amendment to the bill was tabled by Labour. It was defeated heavily, but it may have swung the subsequent vote against the government.

The amendment advised caution, and argued that it was necessary to wait for more evidence to come out about the chemical weapon attack before military action could be considered. As such it was the more anti-intervention motion of the two. 332 MPs voted against it, 112 more than supported it. Some voting against the motion who were staunchly against intervention, such as Labour shadow cabinet minister Jim Fitzpatrick, who voted against both motions and resigned in protest.

But the voting was mainly along party lines. The motion’s defeat could be seen as a blow for the doves and a boost for the hawks. If Labour’s amendment had failed, the coalition’s motion should easily be passed, which was the consensus beforehand.

Immediately following the amendment’s shock defeat, the vote was held for the government’s motion. Given the timing it would be a surprise if one had no effect on the outcome of the other. And, though counterintuitive, Labour’s defeat may have condemned to the coalition too.

Many coalition MPs were uneasy about military intervention, and the signal from the previous vote may have made them think that they could rebel without jeopardising the result – they assumed they would be on the losing side. Any undecided MPs may have inferred that Labour’s amendment stood as an alternative to the government’s plan.

The idea of ‘anchoring’ describes how being exposed to even completely arbitrary numbers skews guesses of amounts, towards the arbitrary number. Estate agents use it with asking prices, which even if they are unrealistic drag the eventual selling price up. In this case, the number wasn’t arbitrary but an extremely relevant indication of the opinion of parliament on the issue at hand. MPs could be forgiven for thinking that the result of the first vote would predict the second.

Even if the result of the first vote was largely predictable, its salience would have been high going into the second vote. Any estimation of the likely outcome of the second vote may have been anchored by the first.

Another popular science idea which is relevant is the wisdom of crowds – the idea that collectively, a large group of people come to the right amount  when their guesses are averaged out. This has been found to occur only when the individuals are acting independently, and are using all available information. The consensus that the government motion would be passed failed to take into account the narrowness of the immediate influences on MPs – they were all attuned to the result of the previous vote.

The first vote also framed the second one differently. Having voted against the amendment, voting for the government motion meant twice supporting military action. This takes more conviction than simply having to make one choice. Voting against both would be seen as the more moderate choice. It’s like a car salesman offering more expensive added extras, just to make the cheaper ones seem more reasonable.

Only a fraction of MPs need to have been swayed to change the result. It was defeated by 13 votes – a margin of 2.3%. If 7 MPs, or 1.25% of MPs had voted yes instead of no, the motion would have been passed. The 30 Tory and 9 Lib Dem rebels more than account for the outcome. On top of this, the 32 Tory and 15 Lib Dem abstentions could easily have changed the result. The shock that met the result, especially inside the Conservative party, shows that the party leaders thought they had their party behind them in the run-up to the vote. It may have been a spur of the moment decision for many of the rebels.

Given the slim margin, was the PM right to claim that ‘it is clear parliament doesn’t want action’? Compare this with the coalition’s confidence that it was the Assad regime that carried out the attack. Earlier on in the day BBC News reported that the UN report said it was 80% confident that it was the Assad regime. Scientific findings require 95%, or preferably 99% certainty in a result before it can be published.

Surprise results are by definition rare and unpredictable, but by tabling amendments that change the ‘choice architecture’ of an issue, could political parties influence the outcome of key votes in their favour?

Life History Theory and Inequality

Here’s a longer piece on how inequality is activating an evolved strategy of living fast and dying young. It’s a theory of the evolutionary logic behind the seemingly maladaptive behavioural responses to inequality which cause so many health and social problems. A great article along the same lines can be found here.



Life history theory has been used to explain clusters of socially problematic behaviour, which are often theorised to be a response to deprivation. In social epidemiology, income inequality has repeatedly been posited as a contributing factor in a wide range of negative health outcomes, independently of average income. Various other social problems have been linked with income inequality at a population level. Both life history strategy and outcomes associated with inequality show a social gradient – strategies are faster and outcomes are worse in lower socioeconomic status groups. The evolutionary rationale of life history strategy is to use behavioural flexibility to respond appropriately to the environment. Harshness and unpredictability engender faster strategies, and inequality may be a signal of these properties. Inequality manifests itself with a positive skew, which disadvantages a disproportionate section of a group. Additionally, status hierarchies which are more stratified in more economically unequal societies are psychologically salient and may act as an independent cue. As such, inequality is predicted to favour faster life history strategies, resulting in the worse outcomes that have been linked with inequality. Faster development, earlier reproduction, future discounting and heightened social competition contribute to problems like teenage pregnancy, worse health behaviours and homicide. The mechanisms by which inequality affects the various traits of life history strategy need to be elucidated in more detail. Reducing inequality would be a way of preventing some of the harms of the fast life history strategy.


Life history theory

Attempts have been made to apply evolutionary psychological research to public policy on issues like teenage pregnancy (Dickins, 2012) and substance use (Richardson & Hardy, 2012). This approach draws heavily on life history (LH) theory; which proposes that humans react flexibly to environmental conditions. Facultative behavioural strategies have evolved in response to variation in our ancestral environment, and the strategies develop under the influence of environmental circumstances. LH theory usually refers to either the harshness or unpredictability of environments as influencing the development of fast or slow LH strategies (Ellis et al., 2009).

A LH strategy is a coherent cluster of behaviours which is adaptive to the survival and reproductive constraints of the environment. So a fast LH strategy involves traits like early menarche and pregnancy, a higher number of low birthweight offspring, shorter birth spacing, shorter breastfeeding, lower parental investment, smaller adult body size and lower longevity. This strategy evolved to minimise the risk of death before reproduction, spread the risk of offspring mortality, and prioritise reproduction over growth – adaptations to harsher or more unpredictable environments (Ellis et al., 2009). In industrialised societies, despite early mortality rates being negligible compared to those in the environment of evolutionary adaptedness (EEA), there must still be cues that modulate LH strategies.

Income inequality

Figueredo (2006) linked the cluster of behaviours that constitute the fast LH strategy to co-occurring socially undesirable behaviour in a wide range of bodies of research, from those in drug abuse to divorce to psychopathology. Similarly, though at a population rather than individual level, income inequality is a predictor of numerous problem health and social outcomes, both in rich countries and in the 50 American states (Wilkinson & Pickett, 2009) – unless otherwise stated, this is the source of all correlations with income inequality. A number of these outcomes are also predicted by the fast LH strategy. Outcomes which are worse in more unequal countries have a social gradient – they are more common in lower socioeconomic status (SES) groups. The fast LH strategy shows a similar social gradient. In general though, LH theory tends to be used to explain differences between either species or individuals – differences between groups are either by SES (e.g. Nettle, 2010a) or comparing subsistence to industrialised societies. LH theory is not usually used to explain differences between industrialised countries with similar average SES.

Health and social outcomes

Teenage pregnancy is a direct measure of LH strategy, and rates are higher in more unequal countries. Dickins (2012) proposed a LH approach to understanding teenage pregnancy in the UK, with relative poverty as a driver.

Other measures can be argued to be indirect measures of LH strategy. Infant mortality is higher in more unequal societies, which may be due to lesser maternal physical investment in each child – average birthweight is lower in more unequal countries. The slow LH strategy minimises the risk of infant mortality and ill health (Figueredo, 2006), whereas health is traded off for earlier reproduction in the fast LH strategy. Inequality predicts worse health outcomes later in life too, for instance higher rates of obesity. Metabolic syndrome, which includes central fat deposition and insulin resistance, can be programmed during early life by changes in the nutritional environment (McMillen & Robinson, 2005). This is thought to be a facultative LH response to unpredictable food supply. It is not clear why inequality would trigger this response, though it may be due to dominance status having determined access to resources in the EEA. Stratified incomes may represent a stratified dominance hierarchy, which puts a premium on status, with low status associated with poor access to resources. Adult body size is another LH trait that is predicted by inequality – height correlates negatively with inequality, conversely to obesity. Longevity is sacrificed in the fast LH strategy, and life expectancy too is lower in more unequal countries (Wilkinson & Pickett, 2009).

Daly et al. (2001) demonstrated that the best predictor of homicide rates in American states and Canadian provinces is income inequality. This relationship holds in a between-country analysis of homicide rates and inequality. Income inequality correlates negatively with life expectancy, but Wilson and Daly (1997) found that inequality has an additional effect to that of life expectancy on homicide rates. International data on crime are non-comparable, but imprisonment rates are higher in more unequal countries. Educational attainment also correlates negatively with inequality. This could be due to the lack of long-term investment in the fast LH strategy.

Mental illness is more common in more unequal countries. This could be due to the highly stressful fast LH lifestyle, with lower levels of social support. Richardson & Hardy (2012) employed a LH approach coupled with a dual process cognitive model to explain substance use. Illicit drug use is higher in more unequal countries. Faster, implicit processing was linked with a fast LH strategy, in particular in unpredictable environments where deliberative processing of context and outcomes is less likely to be valid over time. Other outcomes in Wilkinson & Pickett (2009) as diverse as recycling rates, child wellbeing and women’s status could be argued to result from the fast LH strategy.

An important aspect of the inequality evidence is that not just low SES groups benefit – even higher SES groups show better outcomes compared to their counterparts in more equal countries, on measures like mortality rates, literacy rates, and various health measures (Wilkinson & Pickett, 2009). This suggests that inequality has an effect independent of deprivation.

A case can be made for traits in the fast LH strategy contributing to most of the measures that correlate with income inequality. There could be links between impulsivity and imprisonment, low social support and mental illness and so on.

Does income inequality affect life history strategy?

The high incidence of fast LH traits in unequal countries suggests that inequality, or an aspect of the environment linked to inequality, is a salient cue for LH strategy. It is important to note that correlating the average wealth of rich countries as measured by gross national income (GNI) per capita with the health and social outcomes covered above does not produce significant relationships. Humans are highly attuned to dominance status, and it is likely that we process inequality much like a dominance hierarchy.

The two main properties of the environment that calibrate LH strategy are environmental harshness and unpredictability. It is feasible that inequality is used as a signal of unpredictability, with more variance in people’s circumstances being interpreted as higher unpredictability in access to resources. Inequality may be used in this way to complement longitudinal experience of unpredictability, especially by children. Inequality would be salient to everyone regardless of SES, and so could explain why inequality has an effect across the income distribution.

Environmental harshness is the other main driver of the fast LH strategy, and inequality may act as a cue of harshness, or possibly uncontrollability – the inability of avoiding a deleterious event (Brumbach et al., 2009). Social mobility is highly negatively correlated with income inequality (Wilkinson & Pickett, 2009), so the more unequal a society, the less an individual can negate the risks associated with low SES by investing in growth and fewer offspring. The higher extrinsic mortality rate may change the adaptive value of various preventative health behaviours, so explaining their social gradient (Nettle, 2010b). Pickett et al. (1997) posit that homicide rates and teenage pregnancy may be evidence of a sex-differentiated response, with males increasing social competition and females changing their reproductive scheduling. It may be that income inequality is a more salient cue for social competition, whereas life expectancy has more of an effect on reproductive scheduling.

Inequality may signal harshness due to how resources are distributed. By definition, the income distribution becomes more platykurtic (flatter). But additionally, the distribution shows more of a positive skew – there are more people on a comparably low income below the mean, with income and wealth disproportionately concentrated in a small section of the group. Similarly in other hierarchical animals, access to resources like food and mates is often monopolised by a few dominant individuals. While early humans lived in egalitarian bands of hunter-gatherers, both our more primitive and recent evolutionary environments had varying levels of inequality.

It is this skewed distribution, rather than just inequality itself, that is predicted to have been evolutionarily relevant. It appears that inequality reliably manifests itself in this way, favouring the few over the many. The skewed access to resources means that a large proportion of individuals are at a serious disadvantage in the evolutionary essentials of survival and reproduction. In more equal societies by comparison, a much larger proportion of individuals has the means to succeed evolutionarily. The distribution of evolutionary success as measured by survival and reproduction is determined by the distribution of vital resources. The distribution of these resources is mirrored in the income and wealth distribution, because money is the best available measure of access to resources in modern societies.

Faster LH strategies are expected to be triggered by inequality. Evolutionarily, living in unequal groups would have meant a greater risk of lacking resources, increasing the risk of dying before being able to reproduce. Reproductive schedules would have been shortened accordingly. The fact that high-ranking individuals have greatly preferential access to mates means that many males are at risk of not fathering any offspring. As a result, social competition is intensified. In modern societies there is little chance of dying before reaching reproductive age, so the response of early reproduction results from a mismatch between the ancient and modern environment.

Evidence from other literatures

Some evolutionary approaches have offered a functional explanation of other effects of inequality. The average personality is less agreeable in more unequal American states – a response to intensified competition and individualism (de Vries et al., 2011). A preference in women for men with more masculine faces is stronger in countries with lower scores on a health index (DeBruine et al., 2010), which could be adaptive because facial masculinity is thought to signal better health. But a measure of within-country income inequality was found to correlate more strongly with masculinity preference – this could be adaptive because facial masculinity also signals social dominance, which is of more importance in more stratified societies (Brooks et al., 2011).

The difference between male and female mortality rates is predicted by the level of economic inequality in a country – the more unequal a country is, the bigger the sex difference in mortality rates (Kruger, 2010). This finding is consistent with the concept of males showing a bigger increase in competitive behaviour in response to increasing inequality, compared to females, with excess mortality rates driven by external mortality caused by risk-taking behaviour (Wilson & Daly, 1997). Trust is another trait which has been found to vary with inequality. Neville (2012) found that academic plagiarism was more common in US states which had higher levels of economic inequality. This relation was fully mediated by a measure of trust. A functional explanation of inequality reducing trust is proposed, with students evaluating “whether they can afford to behave uprightly when fellow students benefit from dishonesty.”

A different line of evidence on trust comes from public goods games, where players in a group have the choice of contributing from their own resources to the public good, or keeping their own money and free-riding. Wealth inequality between players has a corrosive effect on contributions to the public good, but only when the inequality is made known to the players (Anderson et al., 2004). This mirrors the strong link between income inequality and trust in rich countries. Lack of trust could be understood as a response to elevated levels of social competition, in turn driven by higher payoff variance.

Taken together, the wide range of behavioural effects that have been linked with inequality can be considered a behavioural syndrome that is triggered by excessive inequality. While the various behaviours have already been conceptually grouped (into the fast LH strategy), only individual behaviours have been linked to inequality. The phenomena linked to inequality by social epidemiologists reflect the fast LH traits or their effects, either through faster reproductive scheduling or heightened social competition which lowers cooperation and trust.

Future directions

As the theoretical groundings are interdisciplinary, research could proceed in a number of different fields. Other traits of a fast LH theory that haven’t yet been linked with income inequality could be investigated as they would be predicted to be more widespread in more unequal areas. Candidate traits include the number of offspring per mother, the number of men a woman has children by, and average age at menarche and sexual debut. Such enquiries would be limited by the existence of international data on the traits; more local areas have the advantage of having more potentially confounding factors constant, but income inequality doesn’t always correlate with outcomes over smaller areas (Wilkinson & Pickett, 2009). Additionally, if it is the distribution of income which is the important thing about inequality, median income should be a better predictor of outcomes than mean income or GNI per capita.

The proximate psychological mechanisms by which inequality has its effect on behaviour remain to be elucidated. It may be that local-level inequality is most salient psychologically (Wilson & Daly, 1997), which would render country-level inequality a proxy measure. The theory that cognitive processing limits people to maintaining relationships with around 150 people – Dunbar’s number (Dunbar, 1993) – would suggest that the relevant traits of this group are particularly important to an individual’s perception of LH traits in the social environment. The influence of aspects of the social environment isn’t necessarily conscious however (Wilson & Daly, 1997).

In experimental psychology, priming participants with varying levels of inequality would be expected to elicit varying responses if they were then tested on LH relevant measures. Systematic differences in attraction and personality could be further investigated. In a game theoretical approach, inequality could be introduced into public goods games like the iterated prisoner’s dilemma. A tournament like that run by Axelrod (2006) would be predicted to turn out different strategies as winners under varying conditions of inequality. Cooperation would be expected to be more widespread when inequality is lower, and defection more common when inequality is higher.

If the theory that income inequality pushes LH strategies toward the faster end of the spectrum is supported, this would provide a policy lever for changing LH strategies. The facilitation of the slow LH strategy may be warranted in safe environments with plentiful resources (Richardson & Hardy, 2012). In general, the failure of education campaigns in effecting behaviour change would be more understandable, and policies that alter the social environment would be encouraged.




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Inequality across the board

Mind the income gap

Income inequality is determined by the distribution of incomes throughout society – not just by the gap between the extremes. Two recently reported income related developments illustrate this point.

The first is the news that the Living Wage in London is to increase by 3% (just above inflation), and in the rest of the UK by 3.5%. Boris Johnson and Ed Miliband support the scheme, but only some employers pay the Living Wage. Launching the scheme, the Archbishop of York John Sentamu promised: “The living wage is the fuse that will light this gunpowder that will explode this great demon of income inequality” (it was the 5th of November).

Meanwhile, FTSE 100 executives have seen their basic salaries rising in line with inflation, and bonuses falling. Their only comfort is an increase in the value of long-term share-based incentive plans, leading  to a 27% increase in overall annual earnings. Given that many of these schemes were set up in the economic trough of the recession, it doesn’t take an investment banker to figure out that the only way was up. In addition George Osborne has lent a helping hand by cutting the top rate of income tax from 50% to 45%, giving back at least £40k to those ‘earning’ £1m or more per year.

This disconnect in policy affecting income inequality is mirrored in the campaigns that aim to reduce it within western societies. The living wage campaign focuses on the bottom end of the scale, and wage growth and tax avoidance at the top end is scrutinised by movements like the 1% and UK Uncut. These moderating forces can only help reduce income inequality, but if incomes are pushed towards the average at one end but away from it at the other, the net result is unchanged income inequality – a problem recognised by the New Economics Foundation. Evidence from social epidemiology, behavioural economics and psychology converges on the importance of one’s position in a hierarchy relative to others: relative rather than absolute poverty. Tinkering at the edges of the income distribution may not have the desired effect as long as a complete lack of social solidarity remains between rich and poor.

Even if more workers earn a living wage and the incomes of the 1% are cut, income inequality could remain at its high level due to stagnating wages in the middle (which is of course much closer to the bottom end than the top end). This trend was in evidence long before the recession, with wages around the average barely increasing despite strong growth in the economy. But because this trend is less obvious than in-work poverty or massive bonuses, it has received a lot less coverage and doesn’t have a vocal public campaign  behind it. In the past, unions would have had more power to influence workers’ wages. In countries like Germany, collective bargaining gives workers a say on pay committees. Employee-owned companies like John Lewis give their partners an equal say, leading to a much more gradual pay structure within the partnership.

These are the proven means by which excessive income inequality can be reduced – what is missing is the political will. Income inequality, as measured by the Gini coefficient, is the best single statistic we have to explain the UK’s dire health and social outcomes. There must be an explicit political commitment to reduce the gini coefficient in the long run – anything less is merely good intentions.

May contain artificial colours: Part II

misleading food label

misleading food label (Photo credit: touring_fishman)

Today the Department of Health announced that it has come to a voluntary agreement with the food industry to standardise front-of-pack nutritional labelling. The major supermarkets have all agreed to implement the change by summer 2013. The move has been welcomed as a victory for health campaigners, albeit years later than it could have been enforced through regulation. And without regulation, there is scope for the labelling not being adopted universally outside of supermarket own brands – independent food manufacturers aren’t as committed to the plan.

According to Public Health Minister Anna Soubry: “The UK already has the largest number of products with front-of-pack labels in Europe, but research has shown that consumers get confused by the wide variety of labels used.” The research in question was conducted by the Food Standards Authority, and published in May 2009, but the FSA’s unequivocal advice to make the traffic light system mandatory was ignored until now.

Although it is years after the report made the recommendation, the agreed labelling system will be the one recommended by the report – a combination of traffic-light colours, text indicating high, medium or low levels of nutrients, and % GDA. This combination was one of the most popular systems, and was understood by 70% of consumers tested in the study – a result replicated in a poll launched by The Guardian today, with 71% of respondents so far finding traffic light labelling useful. As such this is an encouraging example of evidence-based policy, which remains the exception rather than the rule in policymaking.

The 70% comprehension rate does however show that there is still work to be done in educating consumers in nutrition. Happily, a survey headlined “Many consumers find traffic lights confusing” on a food industry website found that just 19% of consumers found traffic light labels confusing – implying that an even greater proportion of consumers understood the labels than in the FSA study.

An article on another industry website, following the argument that the traffic light system demonises certain foods, slathers on the nonsense more liberally:

Whole milk and cheese are high in saturated fat and would be labelled red to point this out. Processed meat such as sausages and bacon will also carry a red label, reflecting their salt and fat content.

Industry experts worried that the hybrid labels did not point out that these products are essential as part of a healthy balanced diet.”

Surely the discovery that a healthy balanced diet is impossible for millions of vegetarians, vegans and people in certain religions deserves a wider press. While this dictate can be taken with a truckload of low-sodium salt, a much more sophisticated food-labelling deception continues to mislead consumers.

I wrote last year about the fake traffic lights that Tesco uses in its food labelling system. This was found in the FSA report to lead some consumers to think that the cool colours (blue or green) used on the scheme indicate that products are low in these nutrients – namely fat, saturated fat and calories. Morrisons’ monochrome pale blue scheme was also found to give a false impression of health.

Unsurprisingly, Tesco and Morrisons were the last of the major supermarkets to sign up to the standardised labelling – implying that they have the most to lose from the change. The fact that they have been allowed to mislead consumers for years is a worrying sign for the ongoing ‘voluntary relationship’ between government and the food industry. Without regulation, the food industry can develop ways of influencing  consumers’ decisions to their own ends and to the detriment of public health. The choice isn’t between freedom of choice and a nanny state; it’s between being influenced by either those seeking to maximise profit or those seeking to improve public health.