Are you maternal enough to be a woman? I saw this headline on Scientific American blogs, and was intrigued. As a researcher in intra-sex variation in personality, I was eager to see any reference to maternal inclinations, given that it is the subject of my most recent paper. Hang on a sec? I realised this was about my most recent paper! Both Kate Clancy and Scicurious seemed to have very strong reactions to the paper, and I was quite surprised at their responses. I felt compelled to reply, firstly to clear up several misrepresentations of our paper, but also to provide some balance to the misconceptions about evolutionary psychology as a discipline.

In case you haven’t read them, have a gander at the two blog posts I’m talking about (Framing and definitions: Are you maternal enough to be a women? and The more feminine you look the more children you want. It must be science.)

Before I talk about the blog posts, I’ll give you a quick synopsis of the results of our research. In the first study, we found a significant positive correlation (0.436) in young women (aged 18-21) between urinary estrogen metabolite levels (at late-follicular stage of menstrual cycle) and self-reported desired number of children; that is, women with higher estrogen levels reported wanting a higher number of children, than those with lower estrogen levels.

For the second study, we made composite faces (‘averaged’ the facial characteristics) of women who wanted the most children and the least children, in two independent samples. We asked people to look at the pairs of faces and decide which one they thought looked most feminine. We found that both men and women judged the faces of those wanting many children, to look more feminine, than the faces of those wanting fewer children. Have a look for yourself at the pairs below.

Ok, so back to the blogs. Scicurious admits she got pretty angry after reading this paper and that she found it hard to step back and approach in a scientific manner. Kate was a little more measured. This is the intriguing bit for me. What is it about this kind of research that makes rational scientists get so hot under the collar? They both concede the methods, data, and analysis are sound, and our conclusions were appropriate - we made no wild conclusions of causation (as it is a correlational study). So why all the fuss?

Kate Clancy’s post was titled ‘Framing and definitions: Are you maternal enough to be a women?’ and she writes on the blog titled Context and Variation. So I found it a little ironic to see the paper taken so out of context:

“in the introduction, they point out only the biological underpinnings of maternal tendencies in a way that is essentialized, reduced to an individual’s hormones prenatally and in adulthood...”

Steady on there. Let’s get a bit of context. There are obviously HUGE effects on ‘ideal number of children’ preferences from social, cultural, and circumstantial factors. Who in their right mind would dispute this? This paper certainly does not. But to cover all those in an introduction in a research paper in a specialist journal would be inappropriate, as we were not investigating any of these variables. I could understand the objection, if we had written only about hormones in the context of a broad review paper of maternal behaviour, or a piece for popular consumption in a newspaper. But scientific research is necessarily specific.

We are evolutionary psychologists working in the field of how hormones relate to behaviour; Our research question was investigating possible links between hormones and behaviour (in this case, maternal preferences); We published in the journal ‘Hormones & Behaviour’! Our study follows on from previous research in women demonstrating hormonal and physical correlates of maternal tendencies. All these studies come in the broader comparative context of well established links between maternal behaviour and hormones in many species of animal. And there lies the rationale for investigating this in humans.

Of course there are undoubtedly MASSIVE effects on maternal inclinations from social, cultural and circumstantial pressures. Our results certainly support this. In our sample, estrogen levels could predict 19% of the variance in ‘ideal number of children’. Although this is statistically pretty impressive for a biological correlate of personality (a correlation of 0.436), this still means that 81% of the variance is up for grabs. So that’s the vast majority of variance we can speculate is related to the plethora of social, cultural, and circumstantial variables. But scientific progress is about acquiring little bits of knowledge, one study at a time. No study would, should, or could attempt to answer all the questions, all at once.

Both bloggers criticise our use of a WIERD sample (Western, Educated, Industrialized, Rich, and Democratic). Aside from loving this acronym (which is brilliant!) I have to point out that from a design point of view, when looking at hormones, a sample has to be homogenous; as there is so much variation across ages and ethnicities in hormonal profiles. It is the nature of good research design to try and reduce down the possible confounding variables which would mask any effects if they were present. Further studies should certainly look at samples of different ages, ethnicities, socio-economic backgrounds and across multiple cultures to see if the hormonal associations we found are present in different samples. But this does not undermine the results of this study. We found what we found, no more, no less.

I can’t help but wonder, would all these criticisms be made of a research paper looking at ... hmm let’s say.. genetic variation and osteoarthritis? A paper of this ilk would no doubt be published in a genetics journal, and would not review the lifestyle and other circumstantial factors that relate to arthritis (of which there are many), but instead it would focus on concisely reviewing previous genetics related evidence, providing the rationale for the study. The sample would certainly be homogeneous in terms of ethnicity, in order to minimise confounding variation. The results might show a certain significant percentage of variance in risk for arthritis that can be linked to variants in specific genes. The results would be published, most likely reported in the scientific and popular press. And that would be that – no one would get angry. So why, when it comes to studies like ours, do scientists from other disciplines momentarily forget their scientific training and opt for emotional responses, personal anecdotes, and sweeping generalisations about a broad academic field of study? I can’t help but think there is something about the nature of evolutionary psychology research that makes some people distinctly uneasy.

It seems that evolutionary psychology has got a bit of a bad name. For some, it conjurs up ideas of universals, blanket claims of specialised behaviours, evolved modules in the brain for the smallest of preferences, and ‘just-so’ stories for how behaviours we possess have came to be. No scientific discipline is immune from a few dubious studies. But the overwhelming majority of evolutionary psychology research is none of the above, it is the scientific investigation of preferences and behaviours in humans in the context of evolutionary theory; encompassing human behavioural ecology, comparative psychology and traditional Evolutionary Psychology (EP). It is a relatively young discipline by scientific standards, and early pioneering studies in the late 1980s investigating sex differences (e.g. finding that men prefer youth in a partner, whereas women prefer resources, across 37 cultures, Buss 1989), were the essential building blocks for later work. These ‘main effects’ needed to be established before individual differences and intra-sex variation could be explored. It is this variation which much of the current research in evolutionary psychology investigates.

I felt the final line in Kate Clancy’s blog post was quite inflammatory, which again took our findings completely out of context, much like the emotive headline of “Are you maternal enough to be a woman?”

“Not wanting a baby today, or any day, does not make you less feminine.”

If I’d read this in a newspaper, fair dues, such are the perils of science reported by journalists in the popular press. But on a science blog, written by scientists? I was a little disappointed. It seems to be the proverbial straw-man fallacy, the setting up of a caricatured argument, as it is easier to criticise than the facts. Arriving at the interpretation that our study suggests not wanting a baby makes a woman less of a woman is, at best, wildly out of context; at worst, provocative and misleading.

I think that the two authors’ emotive reactions to the study, may not necessarily have been about what the paper apparently implies to these authors, but rather a reaction to the actual data and what it showed. I think it perhaps came down to how our findings made them feel. Is this paper really so threatening to how we feel about ourselves as women? Only if we seek to define ourselves only in relation to our ability or preferences for having children.

So what if a small proportion of our desire for children turns out to be associated with our hormone levels? So what if it does actually turn out that estrogen is one of the causal factors? So what! What is it that made this notion so repugnant? We should celebrate our diversity in personality and preferences, and embrace all the factors that have shaped us; culture, upbringing, circumstances, and, heaven forbid, some natural biological variation.

A hot topic at the moment is the concept of neurodiversity, it’s mostly used in the context of Asperger’s Syndrome, an area I currently research. But in general, neurodiversity can be applied to any variation in personality or way of being and perceiving the world, that may have partly biological roots. Neurodiversity is about celebrating our differences, and appreciating that there no right or best way of being, no normal and no abnormal, just a whole spectrum of being, with each personality difference bringing its own unique platter of strengths to the table. It takes women of all sorts to make the world go round, of all shapes and sizes, and of all personality styles and types. Finding that there may be some biological links to some of this diversity does not undermine or denigrate all the other experiential factors that undoubtedly shape us.


Buss, D.M. et al (1989) Sex differences in human mate preferences: Evolutionary hypotheses tested in 37 cultures. Behavioral and Brain Sciences, 12, 1-49.

Law Smith, M.J., Deady, D.K., Moore, F.R., Jones, B.C., Cornwell, R.E., Stirrat, M., Lawson, J.F., Feinberg, D.R., Perrett, D.I. (2011). Maternal tendencies in women are associated with estrogen levels and facial femininity. Hormones and Behavior. DOI: 10.1016/j.yhbeh.2011.09.005