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Get Over It: Men and Women Are from the Same Planet

The views expressed are those of the author and are not necessarily those of Scientific American.


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Recent publication in PLoS ONE by psychologist Del Giudici and colleagues [i] has reignited the debate about just how “naturally” different men and women are.   Del Giudici et al. state that their findings of a “pattern of global sex differences…may help elucidate the meaning and generality of the broad dimension of individual differences known as “masculinity-femininity”.”

In a commentary, psychologist Dario Maestripieri [ii] gushes that this study has finally demonstrated that “when it comes to personality men and women belong to two different species.”  In spite of the hoopla and pronouncements that men are indeed from Mars and women for Venus this study, and the commentaries, ignore that trying to assess and explain similarities and differences between human genders and sexes is very complicated and quite messy.  Apparently, it also makes people act a little silly.

There are three major problems with the conclusions being drawn from study:  a) “gender” and “sex” are used interchangeably, b) evolved differences in men and women are not being measured, and c) relevant biological and anthropological datasets are ignored.  Let me just review these problems and leave you with a plea for a bit of sanity and some scientific integrity when it comes to thinking and talking about men and women.

“Sex” and “Gender” are not the same thing.  Sex is a biological state that is measure via chromosomal content and a variety of physiological and developmental measures.  Gender is the roles, expectations and perceptions that a given society has for the sexes.  Most societies have two genders on a masculinity-femininity continuum, some have more.  The two are interconnected, but not the same thing.  We are born with a sex, but acquire gender and there is great inter-individual diversity within societies and sexes in regards to how sex and gender play out in behavior and personality.  There is an extensive body of literature demonstrating this, but many researchers interested only in definitive distinctions between men and women choose to disregard it.

To measure evolutionary differences in behavior within a species is extremely difficult, but there are at least two basic methodological approaches that are required. First, assessments must be comparative across more than one population of the species of interest. Second the traits being measured must have some way of being linked or connected with heritable aspects of human physiology or behavior that has an effect on overall fitness, and they must be assessed via measures that are accessible, and replicable, across different populations in the species.  Del Giudici et al. used a large questionnaire sample of mostly white, educated Americans.  Relative to the global diversity in cultural structure, this is a limited sample and not a comparative evolutionary one for the species.

Their data come from assessments of 15 personality variables using scales such as “reserved vs. warm,” “serious vs lively,” “tolerates disorder vs. perfectionistic,” and “shy vs socially bold.”  These are indeed personality assessments but they are mired in cultural contexts and meanings, not easily transferable across human societies in time and space, and extremely difficult, if not impossible, to connect, quantitatively, to any aspect of human physiology, neurology, or other structured, identifiable, target for natural selection to act on.  Also, these are most likely not static traits of individuals, but rather dynamic states that are fluid over the lifetime.

Finally, when talking about evolved differences in behavior between males and females one cannot make statements like “when it comes to personality men and women belong to two different species”  without noting the biological reality that we are, indeed, the same species.  There are no consistent brain differences between the sexes [iii], there is incredible overlap in our physiological function [iv], we engage in sexual activity in more or less the same patterns [v], and we overlap extensively in most other behavior as well. There are some interesting re-occurring differences, particularly in patterns of aggression and certain physiological correlates of reproduction, muscle density, and body size.  However, anthropological datasets show enormous complexity in how and why men and women behave the ways that they do [vi].  Studies in human biology and anthropology regularly demonstrate a dynamic flexibility and complex biocultural context for all human behavior, and this is especially true for gender.

Del Giudici et al. and Maestripieri are trying to counter Janet Shibley-Hyde’s “gender similarities hypothesis” [vii] because they “know” that men and women are more different than similar.  There are many valid points of contention in regards to Shibley-Hyde’s seminal paper and Del Giudici et al. bring up an important methodological one, but do not provide an actual assessment and analysis of the overall data set and meta-analyses that Shibley-Hyde used [viii].   My concern is not so much with some good back and forth in the peer reviewed literature, rather it is with the blogospheres’ and the public’s response to the article and to yet another flare-up in over simplistic assertions about the way that men and women “are” by nature.

There is something about avidly trying to prove men and women are different, or the same, that makes people lose their mind a bit.  No matter how much some want it to be true, it is just not that simple; there are no clear cut and easy answers to why we do what we do, and why men and women sometimes have problems getting along. To ignore the enormous wealth of data on how men and women are similar AND different and to try to tackle this enormously complex reality via one-dimensional approaches is just poor science.


[i] Del Giudice, M., Booth, T., and Irwing, P. (2012). The distance between Mars and Venus: Measuring global sex differences in personality. PLoS ONE 7(1): e29265

[iii] Eliot, L.(2009) Pink brain Blue brain. Houhgton Mifflin Harcourt., Wood, J.L., Heitmiller, D., Andreasen, N.C., Nopoulos, P. (2008). Morphology of the ventral frontal cortex: relationship to femininity and social cognition. Cerebral Cortex, 18, 534–40., Bishop, K. and Wahlsten, D. (1997) Sex Differences in the Human Corpus Callosum: Myth or Reality? Neuroscience and Biobehavioral Reviews 21(5):581-601

[iv] Anne Fausto-Sterling (2000) Sexing the Body: gender politics and the construction of sexuality Basic Books, P.T. Ellison and P.B. Gray Eds.(2009) The endocrinology of social relationships.  Harvard University Press Pp. 270-293

[v][v] Herbenick, D.,  Reece, M., Schick, V., Sanders, S.A., Dodge, B.,  Fortenberry, J.D. (2010) Sexual behavior in the united states: results form a national probability sample of men and women ages 14-94. J. Sex Med. 7(suppl. 5):255-265

[vi] Nanda, S. (2000) Gender diversity: cross-cultural variations Waveland Press, Donnan, H. and Magowan, F. (2010) The Anthropology of Sex Berg Publishers

[vii] Hyde JS (2005) The gender similarities hypothesis. Am Psychol 60: 581–592.

Agustín Fuentes About the Author: Agustín Fuentes completed a B.A. in Zoology and Anthropology, and an M.A.& Ph.D. in Anthropology at the University of California, Berkeley, and is a Professor of Anthropology at the University of Notre Dame. His current research includes cooperation and community in human evolution, ethnoprimatology and multispecies anthropology, evolutionary theory, and interdisciplinary approaches to human nature(s). Fuentes’ recent books include “Evolution of Human Behavior” (Oxford), “Biological Anthropology: concepts and connections” (McGraw-Hill), and the forthcoming “Race, Monogamy, and other lies they told you: busting myths about human nature” (U of California).

The views expressed are those of the author and are not necessarily those of Scientific American.



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Comments 21 Comments

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  1. 1. naya8 3:45 pm 01/20/2012

    It’s not so complicated to observe the mental difference betweem males and femals. Even in dogs I could observe the obvious difference.It’s true that we are the same species, but sure we have differwnt brain-microstructure.Biologically we have different hormones, then must be there outcomes, not only in muscles and other physical features but also in brain cutting.

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  2. 2. kclancy 5:12 pm 01/20/2012

    Thanks for this thoughtful, comprehensive perspective Agustin. In addition to how well you address the current research, this post serves as a lovely explained for undergrads about why it’s so important to understand the difference between sex and gender, and why we shouldn’t conflate them. -Kate Clancy

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  3. 3. kclancy 5:13 pm 01/20/2012

    Sorry, “explained” should be “explainer” – darn auto correct.

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  4. 4. ec194010 10:43 am 01/21/2012

    If we decide to assert that men and women are not of the same species, then where does this distinction stop? For consistency’s sake, we would have to say that all males and females are of different species, which would throw away the definition of “species” entirely. Thank you for pointing out the inconsistencies and bias in this study: no matter how we argue the facts, men and women are both human, and no amount of passionate but incomplete research can change that.

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  5. 5. nmtucson 12:03 pm 01/21/2012

    Thank you, Dr. Fuentes, for a cogent and reasoned analysis of the deficiencies of Del Guidice’s research and conclusions. It’s no coincidence that our first question about a new baby is “boy or girl?” Several recent studies have shown that our interactions with newborns differ based on our awareness of the answer to that question, which means we do not have access to subjects that have not already been exposed to gender training. Combined with our growing understanding of the plasticity of the brain in response to life experience, this suggests that any effort to detect genetic or biological differences between the sexes must aspire to a much higher and more exacting level of evidence. Research that attributes any and all detected behavior differences to biology, as opposed to something produced in response to gender acculturation, is clearly deficient. Since ethics and the pervasiveness of modern life prevent us from raising children without gender awareness, it may be very hard, if not impossible, to separate culture from biology in this case. That does not justify setting aside the standards of scientific evidence and leaping to unfounded conclusions.

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  6. 6. AdrianaH 1:07 pm 01/23/2012

    Thank you, Agustín, for a great article. As a scientist, I also tend to worry about the popular science press overinterpreting this type of articles. I think many lay people want clear-cut, definitive answers and do not really like to hear: “it’s complicated” “the science is not settled”, let alone critically review methodologies, assumptions, statistics, etc.
    I think people “lose their minds a bit” over the men-women differences (or lack thereof) because there is a lot at stake: gender stereotyping can lead to a lot of unhappiness and missed opportunities. With respect to Mastropieiri’s “bold” statement that women and men are two different species when it comes to personalities, I cannot interpret it as anything else but a desire for attention. Unfortunately, people pay much more attention when this kind of simplistic, supposedly provocative statements are dropped, than when we have an honest discussion of the difficulties discerning biology from environment when it comes to much of human biology, let alone the mind or a complex phenotype such as “personality”

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  7. 7. AdrianaH 1:12 pm 01/23/2012

    Also, I forgot. One little glitch: the link on reference (i) points to this article here in Sci. Am, not the Del Giudice’s PLoS One article.

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  8. 8. Grumpyoleman 9:10 pm 01/23/2012

    You obviously haven’t met my wife. I registered her with the MIB bureau.

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  9. 9. American Muse 9:55 pm 01/23/2012

    Men and Women are different biologically. Live with it!

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  10. 10. ferrox 10:36 pm 01/23/2012

    “Men and Women are different biologically. Live with it!”

    Especially ‘Judge Judy’ AND Kim-divorce-him-over-twitter-in-73-days-Kardashian. Ya know, when God finally holds court and has Judgement Day on December 21, 2012 (I have survived sixty of these raptures since birth!) , I just HAVE to ask Him, ‘ God, when you made woman, how were ya feeling? Was it another one of those days at the Office, God? Was Satan actin’ a royal fool, him and his henchmen-angels and things just kind of got off to a bad start? You made woman…what was it all about? What was it really looking like on the drawing board and fill me in on all the perks and positives. You had this image of Eve and the Kids. Women who never PMS, laugh at all your jokes and can throw a football. Women who KNOW you are not rich, but will marry you ANYWAY! Right Jesus, am I right?!? Women who love you like your daughter did before she hit puberty and lost her friggin’, frackin mind! Mass murderers, the Adolph Hitlers, the Al Capones, the corrupt and fatherless wall street thieving bankers – women poison, stab, kill and flush down the toilet good men so that they can be cheated on by the Bill Clinton and Tiger Woods Glee club members from hell AND then got on the Ophrah Winfrey show and acted like they never saw it coming despite having a college degree, being over 21, and having a small army of women telling them how to get on a talk show after they do it and their mom is their AGENT (Dad died a LONGGGG time ago)! God, do you sing while you work? Do you Like the Eurythmics? Sweet-dreams-are-made-of-this-Man-is-in-for-some-reality-TV! Desperate-housewives-profootball-hussies-will-not-let-the-camera-crew-use-one-of-thirteen-toilets…! Same planet…huh…wellll….PROVE IT!!

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  11. 11. LiliaFuentes 6:09 am 01/24/2012

    Ok, practically men and women are from the same planet but seriously, sometimes the difference is way too obvious. I am a woman and sometimes I completely have no idea of what is going on in my hubby’s mind!
    audio editor free

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  12. 12. MDG 5:22 am 01/25/2012

    I am one of the authors of the PLoS ONE paper. I wish to clarify a few points that may not be obvious from the post:

    1) In the paper, we do not use “sex” and “gender” interchangeably. True, the “gender similarities hypothesis” put forth by Janet Hyde has been mostly applied to studies of sex differences (e.g., in her 2005 meta-analysis), but the label was chosen by Hyde, not by us.

    2) We do not claim that our data, by themselves, support an evolutionary account of human sex differences. Instead, we explicitly note that some sociocultural accounts are also consistent with large differences. That said, I have several disagreements with Dr. Fuentes assessment of the magnitude of sex differences in humans, their explanation, and the neurobiological underpinnings of personality; but the disagreements are based on my own reading of the scientific literature, not on the results of this specific study.

    3) Dr. Fuentes writes: “Del Giudic[e] et al. and Maestripieri are trying to counter Janet Shibley-Hyde’s “gender similarities hypothesis” because they “know” that men and women are more different than similar.” This is Dr. Fuentes’ personal opinion. Speaking for myself, I certainly did not “know” the results of this study in advance. Of course, the existence of non-trivial sex differences in personality was already apparent from the technical literature (including the cross-cultural studies), and as we discuss in the paper, there are a number of common methodological artifacts that tend to deflate them. For these reasons, it was reasonable to expect that, by correcting those artifacts, we would find a larger effect size than usual. Finally, catchphrases such as “more different than similar” and “more similar than different” are virtually meaningless, unless they are tied to precise statistical criteria.

    4) Dr. Fuentes writes: “To ignore the enormous wealth of data on how men and women are similar AND different and to try to tackle this enormously complex reality via one-dimensional approaches is just poor science.” It is unclear what this senstence is about, but if it refers to our paper, I cannot see how it relates. First, we focus on sex differences in personality, not on sex differences across the board. Second, in the paper we report and discuss both similarities and differences in individual personality traits. Finally (and ironically), the method we used fully acknowledges the multidimensional nature of personality, in contrast with most previous studies in the field. The remark about “one-dimensional” approaches might refer to Hyde’s criticism of our paper, to which we replied at length on the PLoS website: http://www.plosone.org/annotation/listThread.action?inReplyTo=info%3Adoi%2F10.1371%2Fannotation%2F8ec31a46-1c5f-402c-a8b4-c1ed45a6cb88&root=info%3Adoi%2F10.1371%2Fannotation%2F8ec31a46-1c5f-402c-a8b4-c1ed45a6cb88

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  13. 13. Mr. Peabody 10:28 am 01/25/2012

    Well, the commentary is certainly consistent with the hypothese that this topic “makes people lose their mind a bit”.
    Cultures around the world agree men and women are different, but disagree on how. I hypothese that if we could include historical but now extinct cultures that seem to have had different sex roles than most extant cultures (e.g. the Sarmatians), we’d find even greater variety.
    The interesting consistency is in the agreement on difference, and the persistence of gender based divison of labor. That would be an interesting topic to investigate! I have seen passing references in some human evolution articles in this magazine, but that’s all.
    On another note, I’ve neither the time nor interest to review the statistical approach in the original paper, but I agree with the author that “assessments must be comparative across more than one population of the species of interest”. When I was a science undergrad many years ago doing research to meet my Soc Sci reqts, I was surprised in the way research papers by Europeans were always full of “Germans do this, Italians do that” comparisons, while American authors always seemed to interview white upper middle class undergrads and then assume they were typical of all people everywhere. It always seemed a weakness from a methodological viewpoint.

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  14. 14. afuentes 11:10 am 01/25/2012

    I appreciate all of the thoughtful comments and especially the response from Dr. Del Giudice. This is indeed an important topic and one that piques everyone’s interest.
    In direct response to Dr. Del Giudice I wish to clarify a few points. Firstly, my commentary was directed at the broader interpretation and popular treatment of the role of evolutionary histories and processes in sex and gender difference research and not directly at the article (Del Giudice et al. 2011). It was the response generated by the article I was responding to and I used the article as a focal point to present my main points. Dr. Del Giudice and colleagues are clear about the limited role the specific data they present in the article have and also point to the possibilities of multiple explanatory pathways. I think the article was clear and well-presented and, as I noted, think that the exchanges between Shibley-Hyde and Del Giudice et al. is exactly the kind of back and forth needed in the peer reviewed literature.
    However, since the author brought up a few points I do want to address them directly. The article, and many related articles in the genre, DO mix the concepts of sex and gender. Personality traits are gendered and thus their measurement is an assessment of a gender pattern. In this case it is nearly impossible to distinguish between actual sex differences (differences based on the genetic and physiological parameters of male or female) and those caused by socialization and the process of becoming gendered. The authors and I may disagree on this point, but I maintain that it is a crucial one, especially if data are then used to construct or evaluate evolutionary hypotheses.
    I state that Dr. Del Giudice and others have specific beliefs about the innateness of psychological differences in men and women based on their own statements (such as http://open.salon.com/blog/judy_mandelbaum/2012/01/11/mars_and_venus_revisited_how_deep_do_sex_differences_go ), and I stand by that position. They could also make the statement that I believe the opposite: that while there are sex differences, gender differences are much larger and that we have little biological data to support most of the assertions about evolved psychological differences in males and females. I find no substantive support in the neurological literature for any claims of significant evolutionary divergence between male and female cognition and neurological functioning. I welcome any examples that I do not know of.
    I want to make the case that readers of this blog and anyone interested in this issue take it on themselves to read broadly in the topic. Don’t “believe” what I or anyone else says, rather, figure it out for yourself. But please be very careful to approach the subject critically and with an open mind: there are no simple answers.

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  15. 15. MDG 1:00 pm 01/25/2012

    Agustin,
    many thanks for your response. I guess I’ll go for a short meta-clarification:

    1) There are multiple ways of defining “sex” and “gender”, and this may be at the root of our apparent disagreement. In some of the psychological literature, people talk about “sex differences” when they compare people based on biological (chromosomal) sex (usually self-reported); the term “gender differences” is reserved for instances in which one also measures individual differences in gender roles or sex-typicality (e.g., “masculinity-femininity”). In this specific sense, our study is about sex differences. I know that this operational distinction does not reflect the complexity of the concepts discussed in your post. However, the definition presented here is also problematic; if followed strictly, it would make it virtually impossible to isolate “pure” sex differences, because genetic factors and socialization interact at all times across development. This is especially true if social roles and expectations are themselves based on evolved differences, so that one cannot treat them as independent causal factors.

    2) I do believe that evolution has played a role in shaping male and female psychologies. Of course this is not the right place for making a detailed argument in support of this statement, and there is no individual study I can cite that offers indisputable proof (as is the case with most scientific issues). My general argument is that the hypothesis that (some) psychological sex differences have an evolved basis fits the evidence (and the theoretical models) better than a 100% socialization account. For an engaging and balanced review of the evidence, I strongly recommend this book:
    http://www.amazon.com/Gender-Nature-Nurture-Richard-Lippa/dp/0805853456/ref=sr_1_5?s=books&ie=UTF8&qid=1327513666&sr=1-5
    On the evolutionary side, here are two fine books I can recommend:
    http://www.amazon.com/Sex-Differences-Developmental-Evolutionary-Strategies/dp/0124874606/ref=sr_1_3?s=books&ie=UTF8&qid=1327513603&sr=1-3
    http://www.amazon.com/Male-Female-Evolution-Human-Differences/dp/1433806827/ref=sr_1_1?s=books&ie=UTF8&qid=1327513749&sr=1-1

    3) My problem was not with you ascribing me those beliefs, but with the implications of the sentence “[they] are trying to counter Janet Shibley-Hyde’s “gender similarities hypothesis” because they “know” that men and women are more different than similar.” I trust you see the difference between this sentence and “[they] have specific beliefs about the innateness of psychological differences in men and women”.

    Again, thanks for the stimulating discussion and for discussing our paper in your post.

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  16. 16. afuentes 6:25 pm 01/26/2012

    Thanks for the response post Marco. It is indeed a difficult area to quantify but, as you note, one where it is very important to at least try. This is exactly the kind of back and forth that is needed on these topics. Hopefuly this inspires our readers to look at all the references noted here and get a good idea what is out there.

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  17. 17. Nag nostic 2:15 am 01/27/2012

    For 95 percent of us humans, “gender” and “sex” are the same thing. Only for those who deviate towards the fringe, does “gender” and “sex” become so complicated.

    It’s so nice being normal.

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  18. 18. D'Bogat 7:09 am 01/29/2012

    I just have a simple question: Are we males closer to the (male) chimpanzees or to a human female? I have read that the genetic difference between the first is a mere porcentage points.
    (Sorry for the clumsiness of my vocabulary)

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  19. 19. nmtucson 3:08 pm 01/30/2012

    Many statements around this issue remind me of another group believed to be biologically different–Jews. In the middle ages, Jews were forbidden to do most kinds of work by law. They *were* allowed to handle money–lend it, trade it, manage it, etc, so they did, in order to feed their families. Not long after this, we find increasing negative references to Jews’ alleged “obsession” with money. They were thus hated for doing the only work allowed to them. It seems to me that many of the differences between men and women, especially those we seem to relish, come about in much the same way. We grow our little girls to be sensitive and tender, then slam them for not being tough enough to work in the business world. We grow our little boys to play rough and aspire to physical dominance, then slam them for obsessing about sports and war. As I said above, unless you can find a population of humans that has somehow avoided imposing gender differences on their infants, you will have a really difficult time proving that apparent differences are biological and not simply cultural.

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  20. 20. lj237209 2:51 pm 02/16/2012

    Dario Maestripieri made an attempt to tackle an issue in which there are several variables that are difficult to define correctly. With that said, I agree that he did poor job in the process, however I think the topic is overall one that will need to be taken using several approaches. Though the data he collected was skewed and no the most reliable it provided data none the less. I think it is important to look at the data he collected as a basis for further and more accurate research. In other words, after reading his article I now know what not to do when doing research. Also, I now have a better understanding for how to approach this topic in regards to research and analysis.

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  21. 21. js274608 2:50 pm 02/24/2012

    I agree that it’s difficult to study the differences between men and women cross-culturally, using the same terms. Cultural context is very important to a study trying to define the level of similarities and differences between men and women. Personality traits and the words we use to describe them can vary in meaning between societies.

    I also agree that trying to come up with definitive results is unreasonable. It is obvious that men and women are different, but to globally label a degree in which that is true wouldn’t be accurate in my opinion. I like the title of this article because it sort of sums up how much we can really say about sex difference; very little outside of general statements.

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