The costs of bearing (many) children in contemporary Israel

Large families, like this one, grow less common as societies industrialise. Yves Hanoulle on Flickr
Large families, like this one, grow less common as societies industrialise. Yves Hanoulle on Flickr

Becoming a parent isn’t easy. Okay, conceiving can be far too easy. But I mean all that stuff about nappies and midnight feeds, and the germs they bring back from daycare, and trying to understand school newsletters. That’s the difficult bit. And for mums, there’s the metabolically taxing business of carrying a baby to term and breastfeeding it. Not to mention the perilous nature of child birth.

In biological terms, reproduction constitutes the costliest thing most animals do. The more eggs an animal lays, chicks it hatches or babies it gives birth to, the less time and energy it has to devote to other things. Like looking after its body.

In the strange corner of evolutionary biology where I spend much of my research time, we talk of trade-offs. Investments in reproduction today exact their toll on the body, reducing both future reproduction and how long an animal can expect to live into the future.

But in humans, these trade-offs tend to be difficult to detect. The evidence rather tantalisingly suggests they exist, but it takes decades to see the effects of reproduction on a trait like survival. On top of that, variation in socioeconomic status, healthcare and diet can obscure trade-offs. Parents who are well-off or who eat well can, potentially, have more kids and live longer than less well-off or well-fed parents, even if having kids imposes a big cost.

Which is why I’m excited about a study published late last year of 40,454 mothers who gave birth to a total of 125,842 children in contemporary Jerusalem. Uri P. Dior and a team of Israeli collaborators followed mothers for up to 37 years after the birth of their first child. And the results provide evidence that having lots of children can hasten a mother’s mortality.

Mums who bore between two and four children were at lowest risk of mortality from all causes. Mothers who had five or more children lived shorter lives, on average. Analysis of the three types of disease responsible for most deaths showed that risks of cancer, circulatory disease and heart disease all rose dramatically in mums who had five or more children.

In fact, mothers with between five and nine kids had about two and a half times the risk of dying of heart disease or circulatory disease as mothers with fewer than five children.

This study adds to historic analyses showing similar costs but far less directly. For example, British aristocrats living between the 8th and 19th Centuries were far more likely to make it to the ripe old age of 80 if they were childless. While the Israeli study doesn’t compare mortality risks with childless women, it does provide a serious estimate of the mortality costs of reproduction in contemporary women.

I would love to see a similar study following fathers. I wrote last year about the effects of castration on male lifespan, and how they support the existence of a link between reproduction and longevity. But how does the effort men make in fathering their children alter their risks of dying?

Such a study is probably some way off, though, because fathers vary far more in the size of their contribution to child-rearing and the family. From the most devoted dads to men whose only contribution to the family was a few ounces of semen. That is not to say mothers’ contributions don’t vary. They certainly do, but gestation, child birth and to a lesser extent breast-feeding at least are currently inescapable aspects of reproduction that exact physiological costs on the body.

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.

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Explaining Schwarzenegger – men, biceps and the politics of getting what you want

This weekend I gained a grudging appreciation for Arnold Schwarzenegger. The Governator, not the Terminator.

Having watched Arnie’s political rise and fall from afar, he always seemed an odd chimera. Lines he’d delivered as the Terminator retrofitted to an ideology he’d borrowed from somebody else. A kind of populist piss-take exploiting name recognition among cinema-going-yet-politically-comatose voters.

But I’ve just read a paper that made Arnie slightly more intelligible to me. Entitled “The Ancestral Logic of Politics” the paper published last week in Psychological Science explored the link between male upper-body strength and assertion of economic self-interest.

The link between what and what?

Exactly.

The short story is that men with big biceps and who are relatively poor tend to be strongly in favour of social welfare, wealth redistribution and other economic programs associated with the political left. More so at least than equally poor but puny men. Whereas the exact opposite is true for wealthy men: the bigger the biceps the more right-leaning the inclination to economic redistribution.

Rational self-interest

In order to understand this finding we need to consider why people take on the political views they do. While people’s politics are shaped by many factors, self-interest is thought to be particularly strong. That’s not to say voters care only about themselves. But rather that an element of self-interest shaped their views.

With this in mind it isn’t hard to see why policies of social welfare and economic redistribution tend to win more support from the poor – they have much more to gain. Likewise, the twin obsessions of plutocrats – slashing spending and cutting taxes – really mean cutting expenditure on welfare and eliminating taxes that redistribute resources to those less fortunate or well-endowed.

If political views are forged out of rational self-interest, then attitudes to redistribution should follow a neat left-right divide, everything else being equal. But they seldom do.

The new paper, by Michael Bang Petersen, Daniel Sznycer, Aaron Sell, Leda Cosmides and John Tooby adds an interesting twist that might explain why the left-right distinction gets so very blurry.

They argue that for most of humanity’s evolutionary past, the biggest, strongest men were best able to assert themselves in negotiations, wrangling outcomes in their interest. Studies of negotiation and conflict in animals show that better fighters consistently gain a disproportionate share of any resource – without having to fight for it. Most negotiations are an ‘Asymmetric War of Attrition’ in which violence need not be deployed but only implied. The possibility of violence alone leads others to concede more than their share.

That’s where the expression “the lion’s share” comes from. Lions contribute little or nothing to most hunts, leaving the hard and dangerous work of killing prey to the lionesses. The lion then moves in and takes as much as he likes – and there is very little any lioness or cub can do about it.

People astutely judge the fighting abilities of other men – mostly by paying attention to upper body strength. And bicep size provides a most conspicuous, reliable cue of upper body strength.

Psychologists have repeatedly shown that men with greater upper body strength feel more entitled to having things go their way. And they become aggressive more easily. The same does not seem to apply – at least not to the same extent – among women.

The link between male upper body strength, fighting ability and dominance is nowhere near as strong today as it has been throughout our evolutionary past. And democratic processes ensure that strong men can no longer wrest political outcomes in their own interest. Or at least they can’t do so by brute strength alone.

Petersen and colleagues argue that we retain many of the psychological mechanisms whereby strong men assert themselves, and weaker men are more likely to concede. And that shows up in the conviction with which stronger and weaker men hold political views that are in their rational self-interest.

But the result does not apply among women.

Interestingly they repeated the same study in three countries: The USA, Argentina and Denmark. The pattern held in all three, although it was weakest in Denmark. I wonder if the lower income inequality in Denmark, and the social benefits of Danish social welfare programs have eroded the link between physical strength and convictions about redistribution?

Am I a robot?

This paper embodies the kind of evolutionary psychology that routinely gets people’s backs up. We often believe our convictions are reasoned, rational and reasonable. To be told that deeper motivations of which we are not even aware might sway our ideologies and beliefs can be awfully confronting.

The authors are not claiming that attitudes to economic redistribution are settled, hard-and-fast by some combination of socioeconomic status and bicep size. The value of this paper is in showing how our evolved biology and our contemporary politics can interlink in interesting ways, creating nuanced individual differences.

Readers of this column will be familiar with my obsessive interest in the links between biology and ideology. Particularly in the sphere of sex and reproduction, where insecurity over paternity, conflict between spouses and divergent attitudes regarding the regulation of fertility all generate deep political currents.

Readers will also know how I despise the idea that biological effects are “hard-wired” (a particularly dull computing metaphor for human behaviour) or immutable. The beauty of evolution, for me, is in the subtle play between biology and environment. Which is why I’m delighted that this simple (though logistically demanding) study has revealed yet another way in which evolved biology adds nuance to our understanding of political behaviour.

I am already thinking about how to measure the importance of the bicep-redistribution link relative to other influences on political attitudes. And about how to dissect the basis for the link?

Does going to gym reshape a man’s political outlook? Or do men more interested in asserting their self-interest politically tend also toward bicep-building exercise regimes?

And does one measure the bicep on the right or the left?

Arnie, the Republican

Arnold Schwarzenegger’s politics should never have surprised me. He may have played the fictional underdog Conan the Barbarian, but his speech at the 2008 Republican convention revealed that Arnie, since he first picked up a dumbbell in Graz, has been about the muscular, assertive kind of masculinity so beloved of Republicans and the right in general:

I finally arrived here in 1968. What a special day it was. I remember I arrived here with empty pockets but full of dreams, full of determination, full of desire. The presidential campaign was in full swing. I remember watching the Nixon-Humphrey presidential race on TV. A friend of mine who spoke German and English translated for me. I heard Humphrey saying things that sounded like socialism, which I had just left. But then I heard Nixon speak. He was talking about free enterprise, getting the government off your back, lowering the taxes and strengthening the military. Listening to Nixon speak sounded more like a breath of fresh air. I said to my friend, I said, “What party is he?” My friend said, “He’s a Republican.” I said, “Then I am a Republican.” And I have been a Republican ever since.


P.S. About my Yoda complex

Those of us who study evolution and its relation to the human condition often note with a mix of amusement and concern for the future of humanity the ways in which the dankest backwaters of the internet distort our words.

Last week’s article on The Evolution of Lying caught the eye of “Creation Evolution Headlines” who managed to wrangle out of it the idea that the paper by Luke McNally and Andrew L. Jackson on which I was reporting somehow demonstrated that science and a rational world view constitute elaborate self-deception (shielding us from the blinding truth of fundamentalist literalism?).

They suggest McNally, Jackson and I all have “Yoda Complexes”. Interesting, because the Urban Dictionary indicates the Yoda Complex “is especially prevalent among political radicals, conspiracy theorists, religious fundamentalists, and schizophrenics”.

I don’t normally draw attention to this kind of nutbaggery, but their article ‘Evolutionists Confess to Lying’ contains such Onionesque self parody that it makes great entertainment.

I also mention it because Jackson (now tweeting as @yodacomplex) tweeted me the link while I was finishing this column. And what should I discover at the bottom of the post? Another incisive takedown – in this case of the Psychological Science paper on politics and bicep size.

I think not this could be a coincidence. THE FORCE, must it be. Hmmmmmm.

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.

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The Evolution of Lying

Ultimately, our ability to convincingly lie to each other may have evolved as a direct result of our cooperative nature.

Thus concludes the abstract of a new paper in the journal Proceedings of the Royal Society B that considers the evolution of “tactical deception” using a theoretic model and a comparative study of primates.

I’m interested to see how the news media handle this paper. Because the main conclusion – that lying is a way of exploiting others’ cooperative behaviour – seems awfully obvious. But I suspect the true value of today’s paper is a bit more nuanced.

Cooperation evolves

Many species – most notably our own – have evolved quite extraordinary capacities to cooperate. We might take cooperation as an obvious facet of life, but long-term cooperative gain requires a willingness to put aside narrow self-interest in the short term. And that doesn’t evolve easily.

Cooperation makes it possible for some individuals to cheat, prospering off the cooperative efforts of others. Cooperate too readily and you might get taken for a ride. Cooperate only grudgingly and you don’t reap the benefits of working together.

Evolutionary biologists and economists find that even the simplest models of cooperation – such as the prisoner’s dilemma game, explained in the video below – can lead to complex rules about when an individual should cooperate and when it should try to cheat.

The prisoner’s dilemma.

Peer into the natural world, and the range of possible behavioural patterns that have evolved to fetter cheating and allow cooperation to flourish becomes even more complex.

Continue reading The Evolution of Lying