Thursday, June 9th 2011
This month, I am taking part in I’m a Scientist, Get Me Out of Here! which is a program that links up teenage students with scientists all over the world. We put together bios, answer questions, and do live chats with them. I am looking forward to the chance to share my vast knowledge of ladybusiness anthropology — and biological anthropology more generally — with students who are looking to find out whether science is boring or fun.
The way this project is set up is that, over the course of the few weeks we interact with the students, they vote us off one by one; the last person left wins 500 pounds to use towards a science outreach project. If I win, I hope to put these funds towards a project that will link young people together to share their stories of how their lives vary, and what impact that has on their biology. My hope is that this project will achieve two goals: first, to get young people to observe their own bodies and biology in order to be more aware of the science that surrounds them, and second, to show them that variation is what is normal. In the teenage years (and even earlier), there is often a lot of peer pressure to fit some culturally-sanctioned definition of “normal.” But what is normal, really, when we all come from such different places and lead such different lives? When we can directly observe how our lifestyle and environment impact our biology, it becomes clear that difference, not similarity, is the true normal.
As a companion piece to my bio, I would like to share why I think it’s cool to study and enjoy science.
Science is fun
I first got really interested in science because of my AP Biology teacher. Mr. Cabral demonstrated his excitement and zest for biology every day. One day I got so caught up in what he was talking about — the potential impact of genetically modified corn on crops throughout the country — that as soon as I got home, I got on our AOL dial-up internet and started digging (this would have been the fall of 1996). I used AOL’s clunky search engine and managed to find several interesting websites that talked about Archer Daniels Midland. I printed it out on three ring binder paper — I think we were out of regular printer paper — and brought it to him the next day. I remember how motivated I was to learn about ADM, and then how that internal motivation was reinforced by how excited Mr. Cabral was by my find.
This was my first experience with the kind of detective work science can entail. Yes you do experiments, you do labwork or fieldwork, you collect samples or make things blow up or work with stuff that smells. And there is a sense in adventure to that. But another important piece of the work of science is setting out with a question, and doing the sleuthing necessary to find out the answer for yourself.
That will never stop being fun for me.
Science is logical
Fun is what got me started on science, the constant sense of discovery and the enjoyment of developing expertise where no one else has it. But what has kept me in science has been an increasing love, even total devotion, to the idea of the scientific method.
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Castle and Beckett, from one of my
favorite detective shows, Castle. |
The scientific method is another place where the metaphor of the detective is useful. A detective has a question: “Who dunnit?” And then, if she’s a good detective, she develops a hypothesis about who she thinks did it, then methodically tests her hypothesis. If she finds her hypothesis is not supported, she produces a new hypothesis to try again, based on what she has learned. If her hypothesis is supported, she likely will want more evidence to continue to better support her hypothesis.
The reason I love this method is that, if you are willing to really become a good detective, you can detect unintentional and intentional bias. Some conclusions in science, especially the older stuff, and especially stuff on humans that is related to sex or race, was biased by the preconceptions of who performed and interpreted the work. The entire field of women’s reproductive physiology is tainted by early, false observations by a twelfth century monk that women are not human, that they have a seven chambered uterus, that women can decide on the sex of their babies by lying down a certain way, and wicked women will choose to have girls (Rodnite Lemay 1992). Even research in the twentieth century indicated that the sweat of menstruating women makes babies die and flowers wilt (Bryant et al. 1977; Freeman et al. 1934; Macht 1924). And of course, none of these things are true.
I believe that reality of science always wins. We are constantly becoming more aware of implicit bias and honest mistakes, we are constantly developing new methodologies to test our questions. My students, or my students’ students, will probably find things wrong with my own work and modify or correct it some day. This is very exciting to me!
Science solves important problems
I am a biological anthropologist. That means that I am interested in human evolutionary biology, and in understanding the interaction of biology and culture in the production of a human being. I think we can all come up with problems science helps solve, from making cars and homes more energy efficient, to saving endangered species. Biological anthropology can help answer these from the perspective of human ancestry, evolution and behavior. For instance, it’s great that we are making cars more energy efficient, but how do we change usage patterns? How do we get people to drive less? Really, how do we get a species that evolved to consider short and medium term problems and be selfish, to think altruistically and really long term?
In my corner of the field, bio anthro can help answer the following (and more):
- How does environment and lifestyle impact our hormones?
- Why do some people have a harder time having babies than others?
- What is the impact of our changing environment, to one where we are sitting around more and eating more, on our health?
- Does psychological stress impact our physical health? Can sexism or racism have real effects on the body?
- How does moving from one country to another change your hormones?
- Is taking the pill good for you?
- Does what you do as a pregnant woman really matter that much to the health of your baby?
And that’s just the beginning.
Anyone can love science
I want more people, and more different kinds of people, to do science. But I also just want more people to realize how exciting it is to read and learn science. Becoming an engaged science reader, even as someone who already is a scientist, has been a wonderful experience for me. I have developed an appreciation for insects, found out about variation in circadian rhythms, and fallen in love with rivers.
I have realized that there is a lot of great science out there, not just biological anthropology, and it’s all worth fighting for. I have taught a lot of non-science majors since becoming a professor – literally hundreds and hundreds. And when I talk to them, many of them explain that the reason they hate science is that someone made them feel stupid: a teacher, a fellow student, sometimes a relative. I’ve heard several explicit stories where a student was told by a teacher that they weren’t good at science. I’ve had students break down in tears as they describe the sexism and racism that has made them decide science wasn’t for them.
And so, because of the rudeness of another person, the oppression of a system, or a series of incidents that just become too much to bear, they turned away from one of the most logical, exciting, and natural ways of thinking about the world. And many began to dislike it, then mistrust it, then not believe anything they heard about it. And who can blame a young person for turning away from a field, if that is what they are up against?
Nothing, and no one, should turn people away from science, because anyone can love science. Even if you never take another class on it or pick up a single textbook, even if you don’t become a scientist or educator or writer or any of the many jobs where you can use science, you can revel in the beauty of a photograph, the stories of triumph over adversity, the excitement of discovery. You miss out on the simple human pleasure of satisfying curiosity about the natural world if you don’t read science. In addition to improving access and eliminating oppression so that more people can excel in science, we need to make it possible for people to just learn and love it.
One of my favorite things about being a scientist is that I get to hang out with other scientists. At conferences, other scientists present talks or posters to talk about their latest research. If you listen closely to these conversations, along with the jargon, and the statistics, and the graphs and tables and lightning-fast discussions of various technical methodologies, you will also hear people abruptly and delightedly exclaim: “Isn’t this just so cool?”
Yes. Yes, it is.
References
Bryant, J., Heathcote, D., & Pickles, V. (1977). THE SEARCH FOR “MENOTOXIN” The Lancet, 309 (8014) DOI: 10.1016/S0140-6736(77)92199-7
Freeman W, Looney JM, and Small RR. 1934. Studies on the phytotoxic index II. Menstrual toxin (“menotoxin”). Journal of Pharmacology and Experimental Therapeutics 52(2):179-183.
Macht D. 1924. Influence of menotoxin on the coagulation of blood. Journal of Pharmacology and Experimental Therapeutics 24(3):213-220.
Rodnite Lemay H. 1992. Womens Secrets: A Translation of Pseudo-Albertus Magnus’ de Secretis Mulierum with Commentaries: State University of New York Press.
Monday, June 6th 2011
Apologies for the re-post, it was the only way to save the post and comments with the correct tags after the Blogger meltdown the other day!
I’ve been accumulating a lot of mother-y links lately, thought I would share. First two Mother’s Day columns that remind us that we shouldn’t just put Mom on a pedestal and give her some chocolate one day a year, but think in a more systematic way about the oppression of women and children worldwide. Read this one by Esther Cepeda, and this one by Nicholas Kristof.
Fertility
Women see Georgia O’Keefe art as erotic around ovulation. I’m not sure this really qualifies as evolutionary psychology, or needs that framework to understand that libido is higher near ovulation, which would increase the chances one would find erotic art extra erotic at that time.
Birth
Chimps give birth like humans. Very cool. I guess we didn’t notice until now because they are so solitary when they birth?
Cesarean sections are a major factor in maternal death. I don’t like how this article seems to blame the mother, given the way interventions seem to shunt many women towards C-sections whether they want one or not. But there are certainly many factors to consider in this issue, including the mother’s past health and the kinds of protocols used at the location where she is giving birth.
Cutting the cord too soon. This is an interesting piece in Time about the timing of cord clamping and its impact on respiratory issues in infants. Many birth centers and hospitals are advocating for a later time to clamp the cord for this and other reasons.
Mothering of all kinds
Hope for teenage mothers. This was a great story about a great program to help teen mothers have more success in school and beyond.
The amount of time a woman breastfeeds is related to her race and income. Not surprising, given that lactation support services are probably harder to come by, and that women who must earn an income can’t necessarily afford to go without pay for twelve weeks (that is the minimum maternity leave we get in the US, based on the Family Medical Leave Act, and most places give only that minimum). Even those women who do manage to get into a rhythm with breastfeeding lose it when they return to work, not just because of those short twelve weeks, but because few employers have workplaces set up for pumping.
Amy Poehler’s acceptance speech at the Time 100. She discusses the many other women (dare I say allomothers?) who support her as she raises her children and has a career. I may have teared up a little. Okay, I shut my office door and cried.
What measles vaccine refusal really costs. This is something parents should care about.
A hilarious account from a father about all the things you need to worry about — and expect to be judged upon — when having a child.
Finally, while this went around the interwebs when Dr. Isis wrote it the first time, re-read her AGORA post about why it’s all right to not be your mother.
Miscellaneous ladybusiness
The enduring gender gap in pay. Sigh.
Michele Bachelet should be everyone’s hero, if what I read in this story is any indication.
We can no longer escape the reality that BPAs (and other associated bisphenols, which unfortunately are what are being replaced in plastics that claim to be BPA-free) are endocrine disruptors that have negative consequences for health. Well, unless you’re Coca Cola. Then you are going to put your fingers in your ears and go “lalala!”
A lovely post on feminist reactions to street harassment. Another, very powerful read: kill me or leave me alone.
An important read about the use of language in journalistic storytelling, and the sexist way the New York Times originally covered the brutal gang rape of a little girl.
Historic STD posters. Were some sexist? Of course. But it only makes me want one for my office more, if for its ironic value.
Tuesday, May 17th 2011
Sons and daughters and differential parental investment
One of my favorite rhetorical tricks is asking my students a question that has an obvious answer based on cultural expectations, but is wrong. So every year, when I start to teach my students about parental investment, I ask:
Who is harder to raise, sons or daughters?
I’ve asked by a show of hands and with iClickers, over the years, and the room of 750 is almost unanimous: daughters are harder to raise. So, then I get off the stage and walk around a bit. What do you mean by that? I ask.
Girls cause more gray hairs.
Girls cause more trouble when they start to like boys.
Girls are more work, and cost more money, since they shop all the time.
Girls talk back more.
And of course, there is always the saying that girls steal some of their mother’s beauty.
So then I show them this:
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| From Helle et al 2002. |
Here is a graph of maternal longevity based on the number of sons or daughters they have. This data was based on a historical population from Finland from 1640-1870 using church records (Helle et al 2002). As you can see, the more sons mothers bear, the shorter their lifespans. You see the opposite for daughters. So sons have a negative impact, and daughters have a positive impact. This same trend has been found in records from a Flemish village (van de Putte et al 2003, 2004), where sons negatively impact lifespan but not daughters. Interestingly, data from church records from the field site where I work in rural Poland provides a slightly different picture: every offspring of either sex reduced lifespan by about 95 weeks (Jasienska et al 2006).
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| From Jasienska et al 2006. |
Once students see these graphs, they quickly realize what is going on. Generally speaking, girls help mothers more at home in terms of chores and alloparenting. And in many cultures, particularly the historical ones studied so far, sons are costly because parents invest more in them, to help launch their own families. Daughters, not so much. In the Polish population, there may be other factors where daughter investment is important, or it is just costly to have so many offspring and you have maternal depletion regardless of daughter help.
Sex bias in parental investment is an important part of understanding both the biology and culture of parenting, and the developmental trajectories of children. The Trivers-Willard hypothesis, which has been tested many times in humans and animals, suggests that parents should invest more in sons when conditions are good, and more in daughters when conditions are bad. That is, when you have lots of resource you should put it towards a son in order to increase the chances he will have high reproductive success, since his is assumed to be more variable and high effort could lead to high reward. But in periods of low resource, daughters are a good bet because they are more likely to have at least some reproductive success no matter what.
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| From Hrdy 1990. |
Of course, differential investment based on resources is further conflated in humans due to culture and, I would contend, our almost universal favor for patriarchy (Smuts 1995). Here is an image of an Indian family waiting at a clinic. There is a mother, an older son, and a twin boy and girl. Notice the extreme difference in health between the infant boy and girl – they are twins, yet the infant girl is emaciated. This is because in this population sons are always fed and cared for first, and whatever is left over, if there’s anything, is given to daughters.
So, parental investment can have real effects on the parent in terms of lifespan, and perhaps also their own future reproductive capabilities. Further, the conditions under which you may have children can vary, but how much a parent chooses to invest in their children varies too.
The piece of this that may be toughest to parse out, particularly in humans, is how the condition of the mother (or parents) can vary, and how that variation impacts the sex ratio of their children. In some species, like red deer, it is easier to imagine a mechanism: these animals have diapause, a period where their embryos are dormant until it is a good time to gestate and bear them. It is easier to insert some kind of selection process into a period where several embryos are all “frozen” and sex has been determined. But what about humans that produce singletons and invest huge, overlapping amounts of support to their children over decades? How would a sex bias based on maternal condition operate? And is there anything the offspring can do about it?
Changes in maternal breast size during pregnancy
It turns out that measurements as easy as stepping on a scale, and knowing your bra size, can begin to unpack the answer. First, a confession: I consider the author of this paper Andrzej Galbarczyk more than a colleague, but a friend. Andrzej is the graduate student who oversaw my Polish field site last season (Mogielica Human Ecology Study Site, director Dr. Grazyna Jasienska). He has translated consent forms and surveys for me and we’ve had many valuable and important conversations about my fieldwork. He is a smart, kind and thoughtful person and scholar. So, I let him see an early draft of this post to make sure I understood his point of view.
Galbarczyk performed an internet survey in Poland with 120 women, where he asked them to report their pre-pregnancy weight and bra size, their bra size directly after giving birth, and the sex of their offspring. He found two notable differences in these women: mothers of daughters weighed less before pregnancy, but had a greater changes in breast size during pregnancy.
The evidence about maternal pre-pregnancy weight is consistent with the Trivers-Willard hypothesis, as mothers who had sons were more likely to be heavier, and thus have more resource to invest. The second significant difference, that mothers with daughters had larger breasts after pregnancy, seems could be argued either way: Galbarczyk argues that it supports Trivers-Willard because mothers of sons could have been devoting more resource to growing their offspring rather than their breasts.
In other animals and primates particularly, mothers of male infants produce more energy-dense milk, yet mothers of female infants may produce a greater quantity of milk (Hinde 2009). And breast size is a pretty noisy signal of milk quality or quantity. So, what is the meaning of this difference in breast size?
Adaptation or physiological inevitability?
Galbarczyk suggests the difference is related to the evolutionary underpinnings of human female breasts. Women develop breasts around puberty, and though they certainly change in size and shape over time, keep them their whole lives. Other animals develop their mammary glands only shortly before lactating and then they regress again. Many contend that human breasts are an honest signal of fertility. This is at least partially confirmed by the correlation between breast size and estradiol concentrations (Jasienska et al 2006).
Galbarczyk thinks that the larger breasts seen in postpartum mothers to daughters may be a way to attract a mate for parental care. Perhaps this would help where she has given birth to the less-favored sex and needs to really convince him to participate; this could be a signal from the mother or the female fetus. Or maybe by appearing more attractive, she can have another reproductive opportunity, which would give her a chance to have a son.
You all know how I feel about evolutionary storytelling. In certain ways I do find this particular argument compelling, from the perspective of the Trivers-Willard hypothesis. But the evidence for the adaptive scenario around breast size is circumstantial.
Also, I don’t want this story to detract from some very interesting data: remember that Galbarczyk found that in this population, mothers of daughters weigh less before pregnancy, and develop larger breasts afterwards. Very cool. So perhaps we should consider a mechanistic, rather than adaptive explanation?
I have two thoughts about this, both related to androgens (androgens are the class of hormone that testosterone falls under). First, I wonder if there is an effect of fetal androgens from a male fetus on breast size. If so, mothers of daughters would have larger breasts simply because they aren’t having their breast tissue growth or density suppressed by androgens. It could simply be physiology that doesn’t have adaptive meaning.
Second, the mothers of sons were heavier before pregnancy. Heavier individuals tend to have higher circulating insulin levels, and the ovary can respond to higher insulin by producing more androgens (Poretsky 1991, Dimitrakakis et al 2004). So you could have a suppressive effect on breast size from that avenue as well. You don’t need an adaptive scenario for either of these mechanisms, just a consequence of how hormones work.
I would love to see Galbarczyk or someone else follow up on these thought-provoking results by measuring women, rather than relying on self-report, and by measuring their estradiol, progesterone and androgens. Understanding the different factors and motivations that lead to sex differential investment and outcome is a great field of study, and this work gets us thinking in a new direction.
References
Dimitrakakis C, Jones RA, Liu A, & Bondy CA (2004). Breast cancer incidence in postmenopausal women using testosterone in addition to usual hormone therapy. Menopause (New York, N.Y.), 11 (5), 531-5 PMID: 15356405
Galbarczyk A (2011). Unexpected changes in maternal breast size during pregnancy in relation to infant sex: An evolutionary interpretation. American journal of human biology : the official journal of the Human Biology Council PMID: 21544894
Helle, S. (2002). Sons Reduced Maternal Longevity in Preindustrial Humans Science, 296 (5570), 1085-1085 DOI: 10.1126/science.1070106
Hinde K (2009). Richer milk for sons but more milk for daughters: Sex-biased investment during lactation varies with maternal life history in rhesus macaques. American journal of human biology : the official journal of the Human Biology Council, 21 (4), 512-9 PMID: 19384860
Hrdy, S. (1990). Sex bias in nature and in history: A late 1980s reexamination of the “biological origins” argument American Journal of Physical Anthropology, 33 (S11), 25-37 DOI: 10.1002/ajpa.1330330504
Jasienska G, Nenko I, & Jasienski M (2006). Daughters increase longevity of fathers, but daughters and sons equally reduce longevity of mothers. American journal of human biology : the official journal of the Human Biology Council, 18 (3), 422-5 PMID: 16634019
Poretsky L, Seto-Young D, Shrestha A, Dhillon S, Mirjany M, Liu HC, Yih MC, & Rosenwaks Z (2001). Phosphatidyl-inositol-3 kinase-independent insulin action pathway(s) in the human ovary. The Journal of clinical endocrinology and metabolism, 86 (7), 3115-9 PMID: 11443175
