Why inequality undermines societies – an evolutionary perspective


This article originally appeared on Contributoria, at .

The level of economic inequality within countries has been linked to a range of worse health and social outcomes. Evidence from the evolutionary behavioural sciences of how we have evolved to react to our environment may shed light on why we fail to flourish under extreme inequality.

Five years ago The Spirit Level was published, bringing into the mainstream the evidence on the harms of economic inequality. The two academics behind the book, Richard Wilkinson and Kate Pickett, drew on research in the various social science disciplines involved in their day jobs. They went beyond their own field of social epidemiology to show that more unequal societies are not only less healthy, but have worse outcomes on myriad other measures. It’s worth listing these to emphasise the diversity of inequality’s ill effects: infant mortality, child wellbeing, educational attainment, teenage births, social mobility, obesity, mental health, drug abuse, trust, altruism and cooperation, violence and homicide, imprisonment, foreign aid, and environmental sustainability. In the years since the book was published, inequality has become a major political issue internationally.

The explanations which are put forward to explain the effects of inequality usually focus on our immediate responses. Biologically, our levels of stress hormones rise; behaviourally, we become more prone to compete and be aggressive with others; psychologically, we become anxious and obsessed with our social status. But that’s where most explanations stop asking why – short of asking ‘why do we respond in these ways to inequality?’ On one level, it’s sufficient to know the proximate causes and ignore the ultimate causes, but this misses an opportunity to learn something instructive about human nature.

“Why do we respond in these ways to inequality?”

To go beyond the visible and measurable factors, a more expansive timeframe is needed. As a species we evolved over millions of years – for physical traits, this is uncontested scientifically. There is more vigorous debate over the extent to which mental traits have been subject to natural selection. Evolutionary psychology is often thought to portray traits as genetically determined, innate and fixed. While this is an approach that some academics take, it is clearly inappropriate to apply this to the inequality evidence. However, the responses to inequality appear to be consistent across societies. This indicates that there are adaptive traits which respond to inequality systematically – we have evolved the ability to adjust to our current situation.

This principle of calibration to the environment is well established in the evolutionary field of life history (LH) theory. It characterises a strategy which we take throughout life as a trade-off between growth and reproduction. At any given time, we can invest (unconsciously!) biological resources in growth at the expense of reproduction, or vice-versa. Ideally, we would take time to grow for as long as possible to ensure long-term health, before bringing the next generation into the world. This wasn’t always possible in the ancestral environment we evolved in – famine, war, diseases and other components of ‘environmental harshness’ all reduced life expectancy. With such considerations, it would have been no good taking your time to develop, only to die before you could reproduce. Rather, the onus is on as quickly as possible getting to a state where you can pass on your genes.

What results from the trade-off is a scale of LH strategies from slow to fast. In an uncertain environment, early maturation and reproduction protect against the risk of dying before reproducing. Other traits typical of the fast LH strategy include having more children, as a hedge against high infant mortality, and investing less parental care in them, be it shorter breastfeeding duration or father absence. Babies are born smaller, which leads to lower adult height, but with an increased risk of obesity and certain chronic diseases later in life.

The obvious objection to applying LH theory to modern problems is that thanks to developments of civilisation like modern medicine, sanitation, and the rule of law, we no longer really need to worry about making it to adulthood. But we’ve simply not had enough time to evolve and adapt to our new environment. The result is a mismatch between the environment we are adapted to and the one we find ourselves in. This is why we still respond to cues of environmental harshness.

It appears that inequality is a cue of environmental harshness which accelerates LH strategies. This is understandable in the context of access to resources – food, shelter, social capital – which are essential to survival. But egalitarianism was the norm for our early human ancestors. They lived in bands of hunter-gatherers, where meat was shared equally in the group regardless of who killed it. We can infer this from the archaeological record, as well as anthropological reports of the few remaining tribes of hunter-gatherers. In these groups, counter-dominance strategies like ridicule and ostracism prevent any one individual from gaining too much power.

“Egalitarianism was the norm for our early ancestors”

Groups became unequal with the advent of agriculture and other developments. Again, this may be too recent for evolution to have taken effect. However, we may have adapted to inequality in ancestral groups of hierarchical primates, prior to the emergence of the Homo genus. Either way, inequality seems to elicit faster LH strategies, whether as a functional adaptation or not.

Our response to inequality goes beyond behaviour directly related to reproduction. Natural selection will have acted on aspects of our biology, psychology and behaviour to form a coherent suite of responses to the social environment. For instance, the rational reaction to living with social stratification is to compete for all you can get, as you’re not guaranteed a fair share. Appeasing those above you in the pecking order while exploiting those below you is the usual result –the opposite of the healthy disrespect for authority found in the egalitarian groups. Sycophantic worship of celebrities alongside demonization of people at the lower end of society may be the modern-day version of these social processes.

The cluster of traits associated with the fast LH strategy share the theme of short-termism. This even extends into the choices we make, in the form of a cognitive bias known as future discounting. When offered the choice of a smaller reward now or a larger reward at a certain point in the future, some are better than others at resisting the temptation of instant gratification. But when the long-term future is uncertain, it’s rational to discount it and take what you can get today. This is another trade-off, between taking a hit for a bigger payoff in the long run, or short-term benefits at the expense of long-term costs.

“When the future is uncertain, it’s rational to take what you can today”

LH strategy has a strong social gradient – lower socioeconomic status (SES) tends to mean a faster LH strategy. Returning to the health and social outcomes of The Spirit Level, a recurring theme is that most of them show a social gradient, with worse outcomes at lower SES. What Wilkinson and Pickett demonstrated was that outcomes that are associated with deprivation are also associated with inequality in itself: average outcomes are worse in more unequal societies. It may be that LH traits follow the same pattern, and that the well-established link with SES can be extended to inequality.

Indeed, the effects of inequality seem to reflect the consequences of the fast LH strategy. More babies being born underweight leads to higher infant mortality. Less parental investment in children lowers child wellbeing. An obsession with social status exacerbates depression and anxiety. A bias to discount the future shortens perceived time horizons, leading to lower educational attainment and lower impulse control in drug abuse. Sustainability and climate change are similarly neglected by a short-term perspective. And a general quickening of life stages shortens childhood, increases teenage births and curtails healthy lives.

Excess inequality can be added to deprivation as a scourge that stunts our growth and flourishing. This inevitably follows from our evolved tendency to react to our social environment. What this means for social policy is that outcomes which have been seen as pathological must be reappraised as contingent responses to our circumstances.

This doesn’t mean that they should be accepted of course. But interventions like education campaigns that appeal to reason can’t solve social problems, when social conditions affect our biology, psychology and behaviour through mechanisms which are outside of conscious control. To get to the root cause, society must be made more equal.



Flannery, K. (2012). The creation of inequality: how our prehistoric ancestors set the stage for monarchy, slavery, and empire. Harvard University Press.

Wilkinson, R. G., & Pickett, K. (2011). The spirit level. Penguin, London

Life History Theory

Brumbach, B. H., Figueredo, A. J., & Ellis, B. J. (2009). Effects of Harsh and Unpredictable Environments in Adolescence on Development of Life History Strategies: A Longitudinal Test of an Evolutionary Model. Human Nature (Hawthorne, N.Y.), 20(1), 25–51. doi:10.1007/s12110-009-9059-3


Ellis, B. J., Figueredo, A. J., Brumbach, B. H., & Schlomer, G. L. (2009). Fundamental Dimensions of Environmental Risk. Human Nature (Vol. 20, pp. 204–268). doi:10.1007/s12110-009-9063-7

Figueredo, a, Vasquez, G., Brumbach, B., Schneider, S., Sefcek, J., Tal, I., … Jacobs, W. (2006). Consilience and Life History Theory: From genes to brain to reproductive strategy. Developmental Review, 26(2), 243–275. doi:10.1016/j.dr.2006.02.002

Griskevicius, V., Ackerman, J. M., Cantú, S. M., Delton, A. W., Robertson, T. E., Simpson, J. a, … Tybur, J. M. (2013). When the economy falters, do people spend or save? Responses to resource scarcity depend on childhood environments. Psychological Science, 24(2), 197–205. doi:10.1177/0956797612451471

Kruger, D. J., Munsell, M. A., & French-turner, T. (2011). USING A LIFE HISTORY FRAMEWORK TO UNDERSTAND THE RELATIONSHIP BETWEEN NEIGHBORHOOD STRUCTURAL DETERIORATION AND ADVERSE BIRTH OUTCOMES, 5(4), 260–274. Nettle, D. (2010). Dying young and living fast: variation in life history across English neighborhoods. Behavioral Ecology, 21(2), 387–395. doi:10.1093/beheco/arp202

Future discounting

Daly, M., & Wilson, M. (2005). Carpe diem: Adaptation and devaluing the future. The Quarterly Review of Biology, 80(1), 55-60.

Griskevicius, V., Ackerman, J. M., Cantú, S. M., Delton, A. W., Robertson, T. E., Simpson, J. a, … Tybur, J. M. (2013). When the economy falters, do people spend or save? Responses to resource scarcity depend on childhood environments. Psychological Science, 24(2), 197–205. doi:10.1177/0956797612451471


Scott-samuel, A., Bambra, C., Collins, C., Hunter, D. J., Mccartney, G., & Smith, K. (2013). THE IMPACT OF THATCHERISM ON HEALTH AND WELL-BEING IN BRITAIN, 44(1), 53–71.

Whiten, A., & Erdal, D. (2012). The human socio-cognitive niche and its evolutionary origins. Philosophical Transactions of the Royal Society of London. Series B, Biological Sciences, 367(1599), 2119–29. doi:10.1098/rstb.2012.0114

Image Paul Anderson [CC-BY-SA-2.0 (http://creativecommons.org/licenses/by-sa/2.0)%5D, via Wikimedia Commons


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.