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Ethics Prof Slams Claims About Why Pregnant Women “Nest”

Evolutionary psychology is among the “scienciest” of the sciences; implicit belief does not require serious evidence

Evolutionary psychology continues to take a beating, as more people reflect on its central claim: Aspects of our psychology, which we think are the products of reason and emotion applied to personal and historical experience, really stem from the survival and reproduction mechanisms of human and other ancestors of whom we have no historical record.

Arianne Shahvisi (above right), senior lecturer in ethics at Brighton and Sussex Medical School, joins philosopher Subrena E. Smith in critiquing of such vast claims. Her focus in a recent article at Psyche is claims about why expectant mothers “nest,” that is, spend a lot of time housecleaning and stocking up.

Now, if you are not an evolutionary psychologist, you might hazard a guess that the expectant mother foresees a time in the near future when she won’t have time for reorganizing the cluttered hall closet and restocking the bare-ish linen cupboard. She’d be right about that, too.

But the evolutionary psychologist, academic or lay, will have none of such naive explanations; it’s all really found in our putative prehistory. Shahvisi offers some examples, including:

– “The need to nest can be as real and as powerful an instinct for some humans as it is for our feathered and four-legged friends,’ says the bestselling manual What to Expect When You’re Expecting (5th ed, 2017) by Heidi Murkoff. ”


– “Why pregnant women are obsessed with tidying and nesting: It’s all to do with their inner cavewoman” (Daily Mail)

She comments,

Nesting is depicted not as a set of rational space-preparation activities for expectant parents, but as a set of irrational, hormonally compelled and evolved behaviours, unique to women. No scientific evidence is cited, but it’s assumed that nesting in humans is an analogue of nesting in other animals – birds, mice, rabbits, rats – for whom it is literal: they build physical nests in which their infants will be born and housed.

Arianne Shahvisi, “Pregnant women ‘nest’. But there’s nothing biological about it” at Psyche

But when Shavisi looked, she could not find serious science evidence for such instinctive nesting behavior in humans. Findings are contradictory and there are no clear physiological markers underlying the practice:

There’s no denying that many pregnant women experience nesting: three-quarters of those polled report unusual amounts of cleaning and tidying. But when the evidence base is thin, questionable and contradictory, why do so many websites, books and magazines continue to describe nesting as hormonally determined? The conventional explanation for these culturally specific behaviours (ordering furniture for the nursery, buying toilet rolls, organising linen) dives straight down to the endocrinological level, and from there back to an ancient evolutionary origin. There’s an attractive simplicity to the story: the infants of those mothers who best prepared their living spaces would be most likely to survive, inheriting the genes for ‘nesting’ and passing them on into perpetuity.

Arianne Shahvisi, “Pregnant women ‘nest’. But there’s nothing biological about it” at Psyche (July 22, 2020)

It’s a cultural thing, really. For many academics and commentators, Darwinism is the “scienciest” of all the sciences. Evolutionary psychology partakes in that privileged position. A Darwinian explanation can be applied to any facet of human behavior, wrapping it up in a neat little bundle of The Truly Explained. It really does not matter very much if there is a dearth of evidence or no evidence at all. In popular science and self-help literature, a Darwinian explanation can stand in very well for evidence.

Shavisi, following Smith (whom she mentions), notes the absence of any mechanism that would tie conventional modern preparedness for a life-changing event to the—perhaps uncertainly human—cave days of yore:

Not only is there no evidence for a hormonal or evolutionary basis for nesting – there are also no studies that demonstrate a mechanism for it. That is, it’s not clear how hormonal changes could bring about shifts in the brain that compel space-preparation activities. And in any event, our understanding of the pressures on early humans is limited. Early humans lived in groups, and survival required cooperation in child-rearing, so it’s not clear that preparing the ‘nest’ would have been solely or even chiefly a pregnant woman’s role. As the philosopher Subrena Smith argues, even if we had more information about the adaptive challenges that our ancestors faced, we couldn’t assume that modern cognitive mechanisms retain the fitness-enhancing functions they once served.

Arianne Shahvisi, “Pregnant women ‘nest’. But there’s nothing biological about it” at Psyche (July 22, 2020)

But, of course, the evolutionary psychologist does assume such things. Untestable assumptions are the basis of the entire discipline and the reason why Smith argues that it fails as a science.

Shahvisi also quotes philosopher Lynn Hankinson Nelson, to the effect that we should seek explanations from evolution “only once we’ve ruled out equally viable alternatives.” And she suggests one:

It’s also worth observing that maternity leave typically doesn’t begin until the third trimester, which is when nesting is reported to kick in. That means women are cleaning and tidying in the window of time between work ending and labour beginning, which looks less like a biological urge and more like pragmatism, or even boredom.

Arianne Shahvisi, “Pregnant women ‘nest’. But there’s nothing biological about it” at Psyche (July 22, 2020)

True, but such an explanation is much too straightforward to be sciencey. It smacks of heretical notions like the reality of the human mind. Evidence-free speculations about the cavewoman, by contrast, reassure many that we are really talking about science here!

And yes, the whole field has long been ripe for a takedown.

Note: The feature photo is by Omar Lopez on Unsplash

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Ethics Prof Slams Claims About Why Pregnant Women “Nest”