Sexual signalling powers the economy

Could there be a more perplexing product than the stretch Hummer? Source: Kenjonbro on Flickr

So many of the products that surround us defy common sense. I’m not talking about the “What do vegans eat at Christmas?” craziness of the Tofurky. Or even the unrealistic-fear-of-germs obsessiveness of the antibacterial chopping board.

Rather, I’m talking about the flashiest manifestations of attention-grabbing consumerism. Designer label clothes, heavy bling, flashy cars and chunky Swiss watches. These products embody what the early economist Thorstein Veblen labelled “Conspicuous Consumption” – products whose main value is to signal the owner’s wealth and status.

Evolutionary psychologists have lately grown animated about the similarities between conspicuous consumption and the flashy status and mating signals used by other animals. Geoffrey Miller devoted much of his 2009 book Spent: Sex, Evolution and Consumer Behaviour to the ways we signal via our consumption patterns.Miller asks:

Why would the world’s most intelligent primate buy a Hummer H1 Alpha sport- utility vehicle for $139,771? It is not a practical mode of transport. It seats only four, needs fifty- one feet in which to turn around, burns a gallon of gas every ten miles, dawdles from 0 to 60 mph in 13.5 seconds, and has poor reliability, according to Consumer Reports. Yet, some people have felt the need to buy it— as the Hummer ads say, “Need is a very subjective word.”

The answer, according to Miller, is that apart from the starkest necessities, most of the products we buy are purchased to signal our status, intelligence and personality traits. Our need to do so evolved long before the products themselves existed, and the best brands and marketing campaigns (think Apple, BMW and Rolex) tap into these evolved needs.

Today we ornament ourselves with goods and services more to make an impression on other people’s minds than to enjoy owning a chunk of matter—a fact that renders “materialism” a profoundly misleading term for much of consumption. Many products are signals first and material objects second. Continue reading Sexual signalling powers the economy

Menopause as a consequence of within-family conflict


A large Finnish family including several generations. Image courtesy Dr Virpi Lummaa.
The Conversation

Humans are pretty odd animals. Any list of our odd features would be a long one, but menopause would have to come in right near the top.

Where men’s capacity to reproduce diminishes steadily at about the same rate as our bodies age, women stop reproducing around the age of 50. That’s well before the diseases of ageing really kick in.

The fact that women stop producing babies when they still have many years to live challenges a simple reading of evolutionary theory. Surely women who kept on reproducing would have left more descendants – all bearing their genes for late-life mothering?

A lot of evolutionary thinking about menopause centres on the costs of dying in childbirth and the benefits provided by grandmothers. By stopping reproduction and thus living long enough to help raise their grandchildren, grandmothers contribute to their ongoing evolutionary fitness.

But can they contribute enough to make it worth foregoing their own reproduction? Especially since grandchildren each carry only a quarter of their grandmother’s genes, whereas sons and daughters carry half their mother’s genes. The genetic calculations suggest women should keep on making babies of their own rather than retiring to become full-time grannies.

But theoretic modelling by Michael Cant and Rufus Johnstone suggested in 2008 that conflict within the family provides the missing ingredient in our understanding of menopause. A study published today in Ecology Letters provides compelling support for this idea.

When a woman’s first children grow up and start to produce children of their own, those adult children compete for the same resources that the woman might herself use to produce more babies of her own.

Mirkka Lahdenpera, Duncan Gillespie, Virpi Lummaa and Andrew Russell analysed 200 years of data from Lutheran parish records in pre-industrial Finland. I have written before about the extraordinary work done by Lummaa and her collaborators, testing ideas about evolution in historic populations. In this case, they studied records of 653 women born between 1702 and 1823 who had 4703 offspring and 9164 grandchildren in total.

For these women, there were a relatively small number who, between their mid-thirties and menopause, were giving birth to children while their older children were already reproducing. Reproducing at the same time as a daughter didn’t reduce the survival of either of the newborns (although a study in contemporary rural Gambia found an effect of this type). But reproducing at the same time as a daughter-in-law reduced the survival of both newborns by as much as 66 percent.

Resources were scarce in these populations, as they have been for most people throughout most of history. When the mother and her daughter-in-law have to compete for those resources, both end up faring worse. The daughter-in-law has no genetic interest in the mother’s offspring’s success. Unlike the mother’s daughter who is as closely related to the mother’s new offspring (her full sibling if the mother was still married to her father) as she is to her own babies.

When the genetic relationships and the costs of conflict are combined with the benefits provided by grandmothers and the chances of dying in late-life childbirth, the evolutionary models suggest that it makes plenty of sense for women to retire from childbearing and get busy grandmothering. In evolutionary terms at least, conflict with younger women forces mothers-in-law into menopause.


This is just one of the many evolutionary conflicts that permeate family life. I hope to return to that special relationship between mother and daughter-in-law in the near future.

Comments and Tweets appreciated as always. If you tweet, include @Brooks_Rob

This article was originally published at The Conversation.
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Shutting that whole thing down: Todd Akin, rape, pregnancy and abortion

Like almost everybody else I spoke to today, I was staggered, this morning, to hear Todd Akin’s comments about “legitimate rape” and pregnancy. The Missouri Republican, who is running for Senate, was justifying his opposition to abortion even in cases of rape, when he offered up the following cringeworthy utterance:

From what I understand from doctors, [pregancy resulting from rape is] really rare. If it’s a legitimate rape, the female body has ways to try to shut that whole thing down.

It’s possibly the biggest news story in the world right now, but if you missed it, Nicole Hemmer has done a wonderful job here at The Conversation dissecting the responses to Akin’s comments and their likely campaign-aborting implications.

As Hemmer and others point out, Akin’s comments are very much an extension of the so-called “Republican War on Women”. The Republican party finds itself unfortunately captive to evangelical zealots whose bronze-age cosmology is matched only by an antediluvian attitude to sexuality, sex and reproduction. It should surprise nobody that women (like atheists and homosexuals) are far less likely to vote Republican than men are. What surprises me is how many women do vote Republican.

I couldn’t do justice to just how ignorant Akin must be to even consider qualifying “actual rape” from any other. Fortunately columnists, bloggers and tweeters everywhere have been hard at it since Sunday morning. But what struck me most was his pseudo-medical contention that “the female body has ways to try shut that whole thing down.”

That is an assertion that strays right into my research specialty: the biology of sexual conflict. I’ve written many times before about the fact that the reproductive interests of a man and a woman are seldom perfectly aligned and can be quite profoundly out of whack. A wife and husband who differ on whether to have another child are in mild sexual conflict, whereas a rapist and his victim are – it would be hard to overstate this – at profound odds (evolutionarily and otherwise).

Women and men, like all sexually reproducing animals, negotiate the decision over whether to mate or not. The outcome isn’t always a happy compromise because sometimes the mating is worth much more to one party than the other. But in some species, a female can choose – after copulating – not to use the sperm of a male.

In the Australian Black Field Crickets we use in my lab, the male cannot copulate forcibly with the female. She has to mount him voluntarily and she is unlikely to do so unless he has a sexy song. But once she has mated him and he has attached a bag of his sperm (a spermatophore) to her abdomen, she often chooses to remove it before its entire contents enter her body. This isn’t in the male’s interests and he harasses her to prevent her reaching around and removing the spermatophore.

Perhaps this is the kind of thing Todd Akin had in mind? Post-rape female choice in humans in which women have some kind of adaptation that prevents conception with the sperm of a rapist. I always savour the irony when an evangelical evolves into an armchair adaptationist.

If such an adaptation existed, it certainly doesn’t work particularly well. According to one U.S. study, “national rape-related pregnancy rate is 5.0% per rape among victims of reproductive age”.

My point here is not to get sidetracked in the largely irrelevant biology of whether women can, somehow, discriminate against the sperm of a rapist. I would rather highlight the fact that the way in which women discriminate against men whose children they do not want to carry is by not having sex with them in the first place. A measure of the extent to which a society deserves to consider itself civilized can be gained from the extent to which its citizens recognize this fundamental and inviolable right.

When this right is violated or subverted, be it via incest, or violent coercion, or any other means whatsoever, the result is rape. To suggest that some forms of rape earn that name more legitimately than others is to deny women this right and to defend the agenda of the rapist.

But in societies like ours, there are other very effective mechanisms by which women can choose not to bear a child by a particular man, including a rapist: abortifacient drugs and abortion. Bill Clinton famously asserted that “Abortion should not only be safe and legal, it should be rare”. Even the most ardent pro-choice advocates agree that abortion should be rare, but without legal and safe abortion women fare considerably worse in the messy business of sexual conflict and in society as a whole.

What strikes me about the anachronistic attitudes of evangelicals and their Republican puppets to abortion, contraception, family planning, female economic empowerment and feminism in general is just how unambiguously male these attitudes are. All of these issues are informed by what suits men’s evolutionary and economic interests. Or more precisely by what suited the interests of men, especially rich and powerful men, before the industrial revolution.

An entire political party in one of the most advanced and educated countries on earth has become a caricature of the most basal evolved insecurities about masculinity. They seem terrified of losing control over the means of reproduction and petrified of cuckoldry.


Rob Brooks does not work for, consult to, own shares in or receive funding from any company or organisation that would benefit from this article, and has no relevant affiliations.

The Conversation

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Dating with Darwin: A Win for Megan Head

Former SEX LAB PhD student Megan Head (now at Exeter) and her colleague Amber Teacher (Helsinki) took out second place at NESCENT‘s Evolution Film Festival which ran recently at the first Joint World Congress on Evolutionary Biology.

Their winning video “Dating with Darwin” is a delightful stop-motion claymation video. Congratulations, Megan and Amber!