Riddles of Sexual Selection and Inequality

[Updates at bottom on Matt Ridley response]

Proud by Sherri HogueAuthor Matt Ridley has written much about the economics of evolution and sexual selection (Red Queen, The Origins of Virtue, Genome, The Rational Optimist). He is a very good writer and I do recommend his books. Unfortunately, he occasionally slips in snippets of what appear to be political ideology that are often non sequiturs or that only address a single side of an issue that might have competing considerations that seek a balanced view rather than single, simplistic answers.

Ridley’s latest Wall Street Journal and blog article shows signs of such incomplete analysis of a highly political topic, but he does present a very intriguing question, “Does sexual selection explain dislike of inequality?”. It is also interesting that the WSJ article, despite the same content, poses a different title question, “Does survival of the sexiest explain civilization?”. (I suspect an editor sets the WSJ title.) Both questions rely on the hypothesis that sexual selection of males by females pushes men to acquire more resources and display this status for females via flaunting their wealth, referred to as conspicuous consumption in fields of evolutionary behaviours. This hypothesis is certainly not new itself (Darwin originally proposed it) and there is much evidence for it.

What Ridley is suggesting in the article is much more. The WSJ title on civilization, focused on reference to Jason Collins’ work, suggests this process of seeking greater wealth is what created civilization via innovation. That suggestion is, of course, far too over-simplified for the title question and not my current focus for comment other than to say there is a significant difference between causally related and explanatory value. Adolf Hitler’s parents having sex was causally related to the Holocaust but their amorous activities offer no explanatory value to why it happened. Explanatory value requires predictive power. Sexual selection certainly contributed causally to the progress of civilization, but how much it can contribute to explaining civilization, and which parts of civilization, requires very detailed and thorough analyses.

The inequality question is a little more interesting and directly related. Combined with the article content, the question extends the conspicuous consumption hypothesis a step further to disliking inequality. Ridley does not spell out the exact hypothesis. He implies that dislike for inequality is a product of jealousy and envy brought about by this tendency for a few males to succeed over others. From the article:

Back in the hunter-gatherer Paleolithic, inequality had reproductive consequences. The successful hunter, providing valuable protein for females, got a lot more mating opportunities than the unsuccessful. So it’s possible that men still walk around with a relatively simple equation in their brains, namely that relative success at obtaining assets results in more sexual adventures and more grandchildren.

Ridley summarizes this principle of relative envy over absolute utility as classic sexual selection:

It isn’t the peacock with the big-enough tail that gets to mate; it’s the peacock with the biggest tail.

There is certainly argumentative merit here. However, it only works internal to the facts brought up in the article. In the grander context is has some significant problems to overcome as well as competition for explanatory value.

Sexual Selection Mismatches

Ridley’s hypothesis is based on male jealousy over not having the “biggest tail”. The main problem here is that this cannot explain why women also dislike economic inequality. In fact, it appears that women dislike economic inequality more than men. For example, Millionaire Corner, an online magazine published by Spectrem Group, the “premier research and consulting firm in the wealth and retirement industry”, performed a survey on the perceptions of income inequality. They posed four statements about feelings of differences in wealth levels among Americans. On the two statements that declared the difference in wealth levels was not a problem, women agreed less than men. On the two statements that declared it was a problem, women agreed more than men. The differences were consistent and significant on a relative scale.

Ridley’s hypothesis seems to fail this twice: women should not dislike income inequality and women should not dislike it more than men. Sexual selection works by allowing women to differentiate males to pick the “better” ones (in terms of likely reproductive success via proxy signals). It predicts that women should want more differentiation, not less, and for it to be harder to fake. This is the standard explanation of why the peacock’s tail is so long and ornate. Size, cleanliness, and symmetry are easy to differentiate and hard to fake.

An obvious first step in analyzing Ridley’s sexually selected hypothesis is to evaluate it with respect to indicators and models of sexual selection, something Ridley failed to do.

A classic sign of sexual selection is sexual dimorphism - the tendency for large differences between the sexes such as very large males and small females or peacocks with long, ornate tails and peahens with short, plain tales. Looking at those survey results above we see that, although women consistently have a relatively bigger dislike of income inequality than men, they both have generally similar levels of distaste on an absolute scale. There are no answers with 10% women versus 90% men, for instance. Such a large difference would be a potential sign of sexual selection. Their similar absolute level is a contra-indicator of sexual selection and, for what difference is there, it is the opposite of what sexual selection would predict.

Another indicator of sexual selection is that the trait in question is used during mating rituals or other indications of attraction in the opposite sex. The peacock’s tail is unfurled and displayed during mate selection rituals. Male bowerbirds build intricate bowers - basically their decorated houses and front garden - and females select mates based on the impressiveness of these bowers. Male birds of paradise often perform intricate,dance-like displays

When we’re talking about humans, a pretty good sign of sexual selection in this respect is whether or not people of one or both sexes actually find a trait “sexy”. That men find young women with soft, clean skin and certain body shapes attractive is a good sign that these may be sexually selected. Women’s protruding breasts are a focus of men’s arousal and sexual play (and often to the sexual enjoyment by women), a trait and behavior not found in other apes. (While breasts do become engorged in female apes when breastfeeding, it is temporary and occurs after impregnation, not as part of mate selection.)

Similarly, that women tend to find wealth, social status, humour, confidence, competence, and similar traits sexy is a good sign that these may be sexually selected.

So ask yourself: when making a dating profile, on a first date, or just promoting yourself to the opposite sex, is it normal to emphasize your position on wealth inequality? Is disliking economic equality something either or both sexes tend to find really sexually attractive in the opposite sex? I don’t mean just alignment of interests such as religious beliefs, position on organic farming, or enjoyment of rock climbing; I mean is the dislike of inequality itself something we all tend to emphasize to attract the opposite sex? If not, this might be a sign it isn’t sexually selected.

Another indicator of a sexually selected trait is its use in competition between members of the same sex. The big horns of various species of deer and goats offer good examples. Like the peacock’s tail, these large, ornamental traits can become quite intricate and costly but, unlike the peacock, these are also used in direct physical competitions between males who, quite literally, butt heads to demonstrate their superiority directly.

The competition indicator is the basis for Ridley’s hypothesis, that since conspicuous consumption is used by males to compete with each other for female attention and, indeed, that women tend to select men with wealth and resources. However, this is just standard sexual selection of wealth-seeking and display. Ridley’s hypothesis is that the dislike of economic inequality is sexually selected, not just seeking it. Do males compete their level of dislike of economic inequality against other males? If there isn’t a reality show emphasizing it, I have my doubts.

Finally, there are subsequent, secondary indicators of sexual selection of the above indicators. One example is juveniles practicing the behaviour or emphasizing the trait outside of selection rituals, such as those dances of birds of paradise, play-fighting among males, or caring for pretend babies (e.g., dolls) in young females. I’m unaware of either sex instinctively practicing the behaviour of disliking economic inequality when they are young. I certainly don’t remember playing a game of “Occupy Classroom” as a youngster.

As far as sexual selection indicators go, Ridley seems to be zero for all of them.

Competing Explanations

Assuming the dislike of income inequality is even explainable via natural selection at all (see top of the article about explanatory value), there are better alternatives. The free rider and exploitation problems are much better predictors of disliking income inequality than sexual selection. These evolutionary and economic problems describe characteristics that allow one to exploit the work of others, benefit the same as others without paying the same cost, and fake personal superiority cues without earning them through competitive merit. (For simplicity I will refer to all of these problems as free riders.)

If exploiting and faking are easy then free riders can acquire more assets with less work and hence have much greater opportunity to mate. The exploitation problem in the context of sexual selection predicts that both men and women should dislike suspected free riders, and that women should dislike them more. Men will dislike them because, while they personally work hard to demonstrate their own status, free riders both exploit this hard work for personal gain and do so at the expense of opportunities for the honest men. However, this dislike for free riders is countered by men’s interest in the ability to steal or fake it a little to improve their own status, making them a little less honest. (We all tend to cheat a little on occasion.)

Women, on the other hand, will generally dislike free riders because the very signal they are sexually selecting on requires honesty. Faking superiority or gaining it through non-meritorious means is not of value. If peacocks could easily steal the tails grown by other peacocks and wear them as their own, long ornate tails would no longer suffice as cues of meritorious superiority. They would not demonstrate that the peacock is free of parasites or is so superior that it can handle such a long tail and still not worry about predators. (The latter is the handicap principle of sexual selection.) Rewarding that parasitic behaviour means that more cheats will reproduce and so the signal loses its true value over time and hence would be selected less.

Women won’t universally dislike free riders though, because the ability to acquire assets, even if stolen, still provides resources to their offspring. But it does so with risks of revenge by those males who were exploited so its value is limited compared to earning assets by honest merit. The equilibrium between value, non-value, and anti-value of cheats should tend to be strongly against it since truly superior males offer net better value than fake superior males.

We see this exploitative, free-riding behaviour throughout history. Slavery and private governance (monarchies, dictators, warlords, hierarchical churches) all work by individuals gaining personal value off the work of others and using their power of position to keep out competitors rather than by out-competing them.

Capitalism and democracy are not immune to such exploitation. Monopolies are one version wherein a business that manages to achieve dominance at some point, perhaps early in a new market, uses anti-competitive means to stay in that position. Such means can include predatory pricing, cross-market bundling, exclusive agreements across supplier and distribution chains, defamation of competition, espionage, protection rackets, and even basic threats such as burning down competing stores and factories or breaking the legs of sellers in your territory. This is why we have laws and regulations against such actions and anti-competitive measures are closely monitored. Superiority by out-competing in terms of cost, quality, and value are good for citizens. Superiority at anti-competitive behaviour is only of value to the exploiters and free riders and not to the general public.

Even within a well-regulated society there are means to free ride and exploit. The Ultimatum Game is one such mean. In the Ultimatum Game there is an opportunity for two players to earn a reward, say $100. Player 1 gets to propose a split of the money and Player 2 gets to either accept or reject it. If rejected, neither earns a cent. It is in the best interest of Player 2 to accept any non-zero offer; the small amount offered is still better than nothing. Hence Player 1 is best to offer very little and keep as much as possible, say offer $1 and keep $99.

To be clear, Player 1 has done nothing to earn the $99. They have not demonstrated 99 times the value of Player 2. Yet Player 1 gets rewarded 99 times the amount of Player 2 (or 9999 times if they offered only 1 cent). This is, essentially, free riding. They receive benefit disproportionate to their cost compared to others. Now imagine some work was involved in getting that $100. Player 2 could do all of the work and still get only $1 while Player 1 got $99 for doing nothing at all other than having access to the $100. It is the structure of the transaction that determines benefits, not contribution. (The dynamics of this game can get much more complicated depending on the circumstances. I discussed these variations in a prior article related to unions.)

The Ultimatum Game overlaps with the reality of labour markets. Corporate owners and managers are similar to Player 1 and employees are similar to Player 2. This is not to say they are identical. Owners and managers do contribute much to the success of businesses, as do labourers. However, the relationship also has the overlaid structure of the Ultimatum Game, especially taking into account the larger labour markets. (The linked prior article covers this in more detail.) It is impossible to separate the parts of wealth compensation to owners and managers that are due to the value of their contribution from those of the Ultimatum Game structure itself. It is really a mix of the two.

This explains the dislike of economic inequality in terms of differences perceived to be out of proportion to contribution. Few people, if any, seem to perceive a problem of relative wealth inequality when the comparison is between a person who works very hard and one who is lazy. The Atlantic surveyed a wide demographic of people on income distribution and found they were all fine with a reasonable level of meritorious inequality, but which is much less than the inequality seen today in America.

People inherently value rewarding merit. What they dislike is inequality that seems to be far out of proportion, such as when a CEO and senior managers receive large bonuses despite a company failing. The managers’ jobs are to see that the company on a whole succeeds and despite failing at it they receiving compensation that is hundreds to thousands of times higher than labourers who are performing their jobs successfully.

The free riding problems also explain the dislike of economic inequality in terms of non-competitive tactics. While many anti-competitive activities are regulated, some regulations are removed or ignored either via ideological beliefs (e.g., libertarianism) or by influence of those who benefit such as quid pro quo campaign contributions and lobbying at the political level. They earn money not by competing for it but by influencing the rules and public beliefs that redirect public assets to themselves such as rent seeking.

Ridley’s hypothesis fails in this respect too, then. If it is envy over the biggest peacock’s tail that explains why everyone hates inequality then they should also hate merit. The peacock with the biggest tail actually has the biggest tail. But people by and large support a true, competitive meritocracy. For the most part, people support a level playing field. It is not a tied score they seek; but they want that score to be on merit and not because some players control the rules or the referees.

Then there is the fact that too much relative wealth concentrated with too few people collapses an economy. This is true even in evolutionary terms, and is especially true if the relative wealth is achieved through free riding. Free riders can only survive as long as most of the population are “honest” workers. If free riding takes off then there are more free riders fighting for less honest work to exploit. While zero free riding is unstable since a first free rider will have plenty of effort to exploit, the stable equilibrium will generally include only a small percentage of free riders, and there will be an evolutionary arms race of people getting better at detecting and punishing free riders while free riders get better and foiling detection.

Ultimately, I think the answer to Ridley’s question is likely, “No, sexual selection does not explain dislike for inequality.” It doesn’t fit the predictions of sexual selection, there are other evolutionary drivers that do much better, and the dislike for income inequality may not have any genetic component anyway (beyond the trivial) in which case selection pressures have nothing to do with it. 

Upate [2012-11-19]:

Matt Ridley responded by tweet to suggest that sexual dimorphism isn’t always true in sexual selection and it could be mutually selected, as he suggests at the end of his article. While this is true in principle it negates the analogy used about the largest peacock tail and requires significantly more detailed explanation, particularly for why women simultaneously do prefer the most successful males (which is sexually dimorphic) and dislike excessive economic inequality.

In the article, Ridley argues that women are attracted to wealth and conspicuous consumption, men instinctively seek it to maximize opportunities as a result, and yet “They [people] dislike (and envy) conspicuous consumption”. That is a contradiction and sounds more like self-loathing. (Though, as a friend pointed out, it is possible to “hate the game” and not “the player”.)

There seems to be a lack of explanation for the sexual selection of disliking inequality itself in either sex. Do men select it in women or do women select it in men? If men select it in women then it doesn’t seem to actually have the intended effect of distracting women from the males with the “longest tails”. Where is the selection pressure then? If women select it in men, why would that be? Where is the benefit to women, and where is the selection pressure since men actually do instinctively seek wealth.

Mutual sexual selection requires additional explanation on top of this. What gives sexual selection its name is that it is a trait in one sex that is selected by the other for choosing a mate. To be mutual sexual selection requires that it work in both directions and it doesn’t even seem to work in either direction here. Ridley’s suggestion is one of co-parenting in humans (unlike peacocks and peahens).

This certainly puts us further out on the limb of explanation, quickly approaching a “just so” story, but let’s entertain it for a minute. The rare cases of monomorphic mutual sexual selection have been attributed to:

  1. Non-adaptive genetic correlation, meaning one sex selects it in the other and the selecting sex carries the trait themselves since it doesn’t affect the choices of the opposite sex. Here there is no an explanation for which sex has selected dislike of inequality in the other and the explanation given does make it clear that the interests of the sexes diverge: women should want more differentiation in men and men should generally want less of it.
  2. Selection pressure for sexual indistinguishability, usually attributed to avoidance of competition in monogamous flock species. No argument has been made for this, particularly given the premise is based on dimorphic competitive differences of attraction to, and seeking of, wealth.
  3. Weak or absent sexual selection, which is my argument here.
  4. Simultaneous sexual selection resulting from similar male and female parental roles. This appears to be Ridley’s suggestion. The problem is that it only applies if the trait acts as a signal for high quality parenting such as health (e.g., free of parasites), strength (e.g., handicap principle) or nurturing capability. Disliking wealth inequality doesn’t fit this at all. In fact, it should arguably the opposite where parenting improves in both sexes the better each is able to acquire resources. If parenting was equal in hunter-gatherer days, both should be attracted to high wealth status in the other, not dislike it, as long as it is an honest signal.

The alternatives I propose seem to do much better. Men and women don’t hate wealth or conspicuous consumption. They dislike it when it appears to be out of proportion to merit which you would expect from mutual selection pressure against allowing gaming of the “wealth as a competitive merit signal” system. This has nothing to do with jealousy or envy and everything to do with making sure the merit system sends honest signals and penalize free riders, something both sexes should want and women arguably should want slightly more (which they do) because men would want to keep some minor ability to cheat a little for their own sake. This is true even if it is a reasoned, cognitive signal rather than an innate, genetic instinct. It make no cognitive sense either to reward out of proportion of value given.

One detail that we should take from Ridley’s monomorphic suggestion, both in the article and response tweet: it is clear he is suggesting that the dislike of economic inequality is, itself, sexually selected. He could have just meant that dislike is just a form of jealousy and jealousy is a general response of those who don’t compare well to “top” examples of traits: women with small breasts may be jealous of women with bigger breasts, men of low status are jealous of men with high status, and so on. But that jealousy itself is not sexually selected and is cross-gender, so the article would be pointless. Men are not jealous that women have larger breasts than them. Both sexes dislike income inequality as a general principle, not specific to whether it is in men or women. Ridley’s suggestion of monomorphism makes it clear that he proposes the dislike itself is a sexually selected trait.

[Update 2: 2012-11-19]:

A potential confusion occurred to me. The dimorphic behaviour whereby women prefer men with wealth and men instinctively seek it, as Matt Ridley describes in the artlcle (testing with photos, David Petraeus) is clearly a sexually selected trait discussed for many years. The proposed hypothesis in Ridley’s article and blog title refers to the largely monomorphic behaviour of disliking economic inequality and whether it is a sexually selected trait. That is the one I believe doesn’t work.

[Update 3: 2012-11-20]:

Something occurred to me when discussing this topic with a friend. None of what I’m proposing is reliant on my personal opinion of what is meritorious or “fair” compensation, nor on the economic and game theory tactics used to obtain it. I certainly have opinions on that topic. Rather, I’m suggesting that people using their own evaluation of non-meritorious wealth leads to disliking excessive economic inequality, and that such dislike itself is based on innate distaste for gaming the “assets-as-merit” signal.

Where people’s own merit evaluation criteria comes from is another question, but I suggest it is related to proportionality of value to the tribe. Even if people don’t fully understand how many people make their money, particularly in the financial services industries, I think they have a suspicion that CEOs of failing companies should not be getting massive bonuses while labourers doing their job well are getting pay cuts and losing their job, that hedge fund managers making hundreds of millions of dollars per year are probably not providing thousands of times more value than, say, teachers, and that credit card companies earning what is essentially a private tax on all goods and services are not providing the same value back.