Wednesday, July 6th 2011
If you’re on Twitter or read any other science blogs, by now you know that the Scientific American Blog Network has launched. And, I’m pleased to say that I am a part of it! Context and Variation has moved to new digs, surrounded by a network full of bright, interesting people with great communities and great things to say.
But of course, while I encourage you to check out Bora’s post where he introduces every one of us, I have to plug a few bloggers in particular.
First, the University of Illinois is the only university to be represented by three bloggers on this new network (yeah, we totally did a press release for it). Alex Wild of Myrmecos (you know, the guy who comes up if you just google insect photography) has created a blog called Compound Eye that will cover science photography. What’s exciting about this blog is that Alex, true to his nature, will be very generous with his space and will showcase the work of many other photographers.
Joanne Manaster, who you may know as sciencegoddess on Twitter, hosts the blog JoanneLovesScience.com. Joanne is a truly exceptional science educator and puts great attention on reaching young audiences, from exploding gummy bears, the science of makeup, and Kids Read Science programs. On the SciAm blog network, Joanne will be co-hosting a new blog PsiVid with Carin Bondar. This blog will continue Joanne’s work of thinking about engaging audiences and getting them interesting in science in new ways.
In addition to these great U of I bloggers, I also have to mention my fellow anthropologists. Krystal D’Costa is moving her fantastic blog Anthropology in Practice to SciAm. You can expect more thoughtful, detailed, yet readable and fun posts from Krystal. She is a wonderful observer of human nature, and I love how she forces me to be an anthropologist at all sorts of casual moments when I usually take my academic lenses off.
Then there is Eric Michael Johnson’s blog The Primate Diaries. Eric is another very talented writer, sharing insights from a great mind. I have enjoyed his posts on sexuality, primatology, sexism, and human evolution.
Oh, and need I even mention? There are lots of female bloggers on this new, kickass network. Check out The Mary Sue’s coverage. They’re right. The SciAm Blog Network does introduce us to about a zillion new women in the sciences. Incidentally, it does a pretty decent job of introducing readers to people of varying sexualities and ethnicities as well. We can always do better, but it is a strong start.
The people of this network have exceptional voices and important perspectives. And now more people will see what they have to offer. I hope you’ll all join me over at my new place, that you’ll check out the rest of my network peeps, and that you will enjoy helping me bring the ladybusiness to Scientific American.
Friday, July 1st 2011
|Should I advise recently single ScarJo to stay
off the pill to find her next beau? From here.
Imagine you are a single, heterosexual woman. You meet a nice man at the driving range, or on a blind date. You like him and he likes you. You date, you get engaged, you get married. You decide to have a child together, so you go off the pill. One morning you wake up and look at your husband, and it’s like seeing him through new eyes. Who is this stranger you married, and what did you ever see in him?
After some articles made the news when they suggested mate preferences change on hormonal contraception, this seemed to be the scenario in the heads of many women. Is my pill deceiving me? What if my birth control is making me date the wrong man?
Several articles over the years have demonstrated that women prefer men with more masculine features at midcycle, or ovulation, and more feminine features in less fertile periods. Based on body odor, women and men also often prefer individuals with MHC (major histocompatibility complex) that are different from theirs, which may be a way for them to select mates that will give their offspring an immunological advantage. These findings have been replicated a few times, looking at a few different gendered traits. And as I suggested above, other work has suggested that the birth control pill, which in some ways mimics pregnancy, may mask our natural tendency to make these distinctions and preferences, regarding both masculinity and MHC (Little et al. 2002; Roberts et al. 2008; Wedekind et al. 1995).
On the one hand, I think it’s both interesting and important to consider the implications of the birth control pill beyond just contraception. Hormones are messages, so any cells that have receptors for these messages, like specialized mailboxes, can receive them. The pill is made of synthetic versions of estradiol and progesterone, and there are estradiol and progesterone receptors in your brain. And yes, these hormones do change your brain, both during the natural cycle and on hormonal contraception; Scicurious has written well on this in the past.
|Jolie, had she been on the pill and chosen her mate
differently. From here. Yes, looks to be a real pic.
On the other hand, I have a lot of questions: First and most important to me, how does any of this translate to non-straight women? I find the constant focus on mate choice between men and women a bit exhausting, and am not sure we can assume non-straight relationships to work the same way. Next, how well do preferences over the cycle map on to actual choices for mates, short term or long term? If we happen to find Brad Pitt more attractive than Justin Bieber at midcycle, does that mean no one will do but Brad Pitt? And finally, what are all the factors that we need to consider in mate choice besides a deep voice or square jawline (again, especially if you try to expand your thinking beyond straight relationships)?
I’ll start with the last two questions that deal with mate preference versus ultimate mate selection. As you all might expect, women and men choose mates for lots of reasons, not just masculinity or complementary immune systems. Bereczkei et al (1997) looked at singles ads and found women often sought mates with high parental care. In a separate singles ad evaluation, Pawlowski and Dunbar (1999) found that women mostly selected men of high resource potential who were interested in long-term relationships (either unlikely to divorce or unlikely to die within twenty years), where men selected women by markers of fecundity (ability to have babies). In a sample of 18-24 year old straight people in the US, Buston and Emlen (2003) found that most people selected mates who had similar characteristics to themselves. And a speed dating sample showed that people under those conditions selected dates based on easily observable traits, like physical attractiveness (Kurzban and Weeden 2005).
Now on to the fact that all of this research is on straight people. I found very little on lesbian women and the menstrual cycle… but what I found was very cool! Brinsmead-Stockham et al (2008) found that, like heterosexual women, lesbian women are quicker to identify unknown faces at midcycle, as long as they were the faces of the sex they preferred. So straight women were good at identifying male faces, lesbian women good at identifying female faces. Burleson et al (2002) found that sexual behavior in lesbian and straight women was mostly similar through the menstrual cycle, with both peaking at midcycle.
So, mate preference may be about telling a research assistant who is the hottest to you at a particular point in your cycle. And it is a fairly robust and consistent finding. However, when it comes to ultimate mate selection the most important thing to consider is a great point made by Pawlowski and Dunbar: finding a mate is about advertising what you have to offer while making known what you want in a mate. Then it’s all about finding some kind of compromise through a series of trade-offs based on what the individual wants, what they can offer, and what’s available in the dating pool. (So, since neither Brad Pitt nor Justin Bieber are currently in the dating pool, my previous comparison was pointless.)
Those of you who met your mate while on the pill: not to fear. I don’t think that the possibility that you may have some suppression of masculinized preferences at one point in your cycle means you’ve chosen the wrong person.
Who knows, it could have opened you up to the Mr. or Ms. Right.
Bereczkei T, Voros S, Gal A, & Bernath L (1997). Resources, attractiveness, family commitment; reproductive decisions in human mate choice. Ethology : formerly Zeitschrift fur Tierpsychologie, 103 (8), 681-99 PMID: 12293453
Brinsmead-Stockham K, Johnston L, Miles L, & Neil Macrae C (2008). Female sexual orientation and menstrual influences on person perception Journal of Experimental Social Psychology, 44 (3), 729-734 DOI: 10.1016/j.jesp.2007.05.003
Burleson MH, Trevathan WR, & Gregory WL (2002). Sexual behavior in lesbian and heterosexual women: relations with menstrual cycle phase and partner availability. Psychoneuroendocrinology, 27 (4), 489-503 PMID: 11912001
Buston PM, & Emlen ST (2003). Cognitive processes underlying human mate choice: The relationship between self-perception and mate preference in Western society. Proceedings of the National Academy of Sciences of the United States of America, 100 (15), 8805-10 PMID: 12843405
Kurzban R, & Weeden J (2005). HurryDate: Mate preferences in action Evolution and Human Behavior, 26 (3), 227-244 DOI: 10.1016/j.evolhumbehav.2004.08.012
Little AC, Jones BC, Penton-Voak IS, Burt DM, and Perrett DI. 2002. Partnership status and the temporal context of relationships influence human female preferences for sexual dimorphism in male face shape. Proceedings of the Royal Society of London Series B: Biological Sciences 269(1496):1095-1100.
Pawłowski B, & Dunbar RI (1999). Impact of market value on human mate choice decisions. Proceedings. Biological sciences / The Royal Society, 266 (1416), 281-5 PMID: 10081164
Roberts SC, Gosling LM, Carter V, & Petrie M (2008). MHC-correlated odour preferences in humans and the use of oral contraceptives. Proceedings. Biological sciences / The Royal Society, 275 (1652), 2715-22 PMID: 18700206
Wedekind C, Seebeck T, Bettens F, & Paepke AJ (1995). MHC-Dependent Mate Preferences in Humans Proceedings: Biological Sciences, 260 (1359), 245-249 DOI: 10.1098/rspb.1995.0087
Friday, June 24th 2011
|Found here. IUDs are back in style.
Neon sunglasses? Not so much.
What is used by 20-26% of European, 30% of Israeli, 34% of Chinese, 34% of Egyptian, and 49% of Korean women… but only 1-2% of US women (Harper et al. 2008)? The intrauterine device, or IUD! The IUD is found in two forms: the copper IUD, and the hormone-releasing IUD that releases a tiny amount of progesterone. Both make the uterus inhospitable to pregnancy.
The modern incarnation of the IUD is possibly safer and more effective than oral contraception. Chances of pregnancy on the IUD range from 0-1.1 per 100 woman-years of use, and they get lower with each year you use it (Prager and Darney 2007). That is far better than your chances on the pill.
The IUD suffers from a bad reputation, in part due to misinformation or misunderstanding on the part of medical providers. Harper et al (2008) surveyed 816 physicians, nurse practitioners and physician assistants who each serve more than 100 contraceptive patients per year in the California State family planning program. They found that 40% of medical providers didn’t offer IUDs to patients, 36% provided infrequent counseling. Further, 46% thought nulliparous women, and 39% thought postabortion women were good candidates for the IUDs. Younger physicians were more likely than older physicians to recommend the IUD (Harper et al. 2008), which suggests a generational gap due to the overinflated descriptions of the dangers of early IUDs.
So let’s go through the actual pros and cons of this form of contraception, so that over the course of the summer you can compare this information to what you’ll be learning about the pill.
Remember, I’m just an anthropologist who studies this stuff. I am not a medical doctor.
Danger danger! Or not
The biggest danger from an IUD is that it could perforate the uterus, or be expelled from it. And that can certainly be painful, reduce fertility, or get you pregnant when you think you are protected. So let’s look at how often this happens.
Prager and Darney (2007) wrote a review on the levonorgestrel IUD (hormone-releasing, like Mirena) in nulliparous (that means no parity, or no children) women. This is important because many still carry the misconception that nulliparous women shouldn’t use IUDs, because of an increased risk of perforation, infertility, pelvic inflammatory disease risk, and difficulty in placement.
There are notable differences between the parous (has had children) and nulliparous (no kids) uterus. The parous uterus is a little bigger, and the cervix dilates a bit more easily. However, it turns out that for the most part these differences are not great enough to produce any differences in side effects or danger to the woman using it.
Prager and Darney (2007) found six studies on perforation or expulsion rates for IUDs (some copper, some hormone-releasing, which are made of plastic and are flexible). They did not find enough data to support a link either way for nulliparity and perforation, because the studies they found had anywhere from zero to two nulliparous women in them. That said, the perforation rates for each study ranged from 0-1.3% in one study, and 2.6 out of 1000 in another (Prager and Darney 2007).
Expulsion rates do not seem to differ between parous and nulliparous women, and again, are very low for all women. The annual expulsion rate among cited studies was 0-4.2 per 100, 0-1.2% per year, and 0-0.2% per year (Prager and Darney 2007). The one important point they do make is that there is a very slightly increased risk of expulsion for lactating women – perhaps this is due to the oxytocin released during nipple stimulation, which could contract muscle?
The other concern sometimes mentioned is that of pelvic inflammatory disease. PID is an infection of the uterus and is usually associated with a sexually transmitted disease. PID can increase the risk of infertility. So for women who haven’t had a kid, but want to some day, the concern about getting PID can loom large.
However, Prager and Darney (2007) surveyed the literature and found that the only studies that support a link between PID and IUDs involves an IUD no longer on the market, or was associated with high-risk sexual behavior.
In some women, copper IUDs can increase menstruation. However, the hormone-releasing IUDs tend to decrease menstruation, and many women stop getting periods altogether. Hormone-releasing IUDs can be prescribed to women with menorrhagia, or pathologically heavy menstruation, too.
Prager and Darney (2007) describe a study in which hormone-releasing IUD users were compared to oral contraceptive users. These IUD users had less dysmenorrhea (painful periods), less spotting, fewer days of bleeding, fewer cycles. Further, 88% of the IUD users wanted to continue with that method of contraception after a year, compared to 68% of pill users, and this difference was statistically significant (p = 0.003).
Romer and Linsberger (2009) also looked at satisfaction with the hormone-releasing IUD in a sample of 8680 women across 18 countries: 95% were satisfied with their method of contraception.
The fine print
Insertion of the IUD can be a little more painful in a nulliparous woman, since her cervix has not dilated before. Also, a minority of women may spot for a while after insertion of the IUD… and by a while, I mean a few months. But once those few months of light spotting are over, they often don’t get a period again until removing the IUD. And of course, the IUD is not conducive to sudden desires to start the babymaking process: you will need to schedule its removal first.
However, with the number of women who are ambivalent at best about birth control pills, but do not want to use a barrier method, the IUD offers a lot in the way of safety, efficacy and ease of use.
Harper CC, Blum M, de Bocanegra HT, Darney PD, Speidel JJ, Policar M, & Drey EA (2008). Challenges in translating evidence to practice: the provision of intrauterine contraception. Obstetrics and gynecology, 111 (6), 1359-69 PMID: 18515520
Prager, S., & Darney, P. (2007). The levonorgestrel intrauterine system in nulliparous women Contraception, 75 (6) DOI: 10.1016/j.contraception.2007.01.018
Römer, T., & Linsberger, D. (2009). User satisfaction with a levonorgestrel-releasing intrauterine system (LNG-IUS): Data from an international survey The European Journal of Contraception and Reproductive Health Care, 14 (6), 391-398 DOI: 10.3109/13625180903203154