This blog is about the intersection between evolutionary biology and food. But also about practical applications, sustainable agriculture, and general tasty things.
There aren't many papers studying sex among foraging people, given that is a potentially taboo topic among all societies. But lately I stumbled upon this paper on the Aka, the pygmy tribe I have written about before. Jesse Bering wrote about how the paper describes a cultures where the homosexual orientation is unheard of. That's not surprising in a culture obsessed with fertility and could also have to do with unusually low levels of sexual dimorphism. What is really surprising to me about this paper is that the married Aka are actually having sex and lots of it:
This chart compares married Aka, with married Ngandu (nearby agriculturalists), and with married Americans.
We are a society obsessed with sex, but sexually unsatisfying marriages are almost a National joke.
When I posted this paper on Twitter though, people seemed most surprised that the men do not masturbate. Maybe they aren't masturbating because they are receiving all the real sex that they want and are in fact quite exhausted from it considering they have to do it several times a night and if they can't get it up their wives will divorce them. They fear this enough that they have developed several botanical viagras from local plants.
Just like the idea of not masturbating is foreign to Americans, the idea that married people aren't obligated to have sex is foreign to the Aka. And because American men generally don't get as much sex as they want, we have a multi-billion dollar industry that factory farms it for us: pornography, another thing many American men can't imagine living without. A large part of many porn-users sexuality is often compartmentalized into a private world of Incognito browser tabs. I wonder if more sexual people would tolerate relationships with people who don't seem to want much sex if it didn't exist.
As for why those people (mainly women) don't want much sex and think part of it is thinking sex needs to be an elaborate production each time and part of it is low-sex drive, which is often caused by poor nutrition. A stunning amount of women have never orgasmed before. The Orgasmic Diet is a low-carb diet supplemented with fish oil that some women have claimed has solved the low sex drive/no orgasm issue. I think the paleo diet probably works a lot better since it emphasizes a lot more libido-enhancing foods than just fish oil and forbids a lot of detrimental foods. Anecdotally I've heard people say a keto diet puts their libido into the stratosphere, but other people have told me it does the opposite.
I was reading the Weight Maven blog and she found this fascinating video series comparing the effects of processed food and pornography on the brain, which is worth watching (they also have a website with more info). It's an interesting new understanding on the phenomenon. We've moved away from understanding overeating as a moral failing and looking at it in terms of hyperstimuli that messes with our brain. That video does the same with our understanding of sexual hyperstimuli. It's probably worth saying though that pornography is better for society than habit of frequenting prostitutes that is more common in some agrarian cultures such as the Ngandu. Other cultures (the Masaai for example) have wife-sharing, which seems to have worked out well in the past, but since the advent of virulent STDs*, it has threatened some of these cultures with extinction.
* it's disputed when really threatening STDs really emerged. There are many ancient skeletons with lesions that could be syphilis, but they also could be a related non-STD disease called yaws. But there have been cases of really viruent STDs in wild animals. It's likely Tasmanian Devils will become extinct in the next few decades because of one.
As interesting as Venus-gate is, I don't think art from the paleolithic really tells us much about the health of the average person. Think of some famous artwork from our era, imagine there is a nuclear disaster and everything is destroyed except that piece of artwork. What incorrect conclusions would a society come to if they just had that piece of artwork? Humans have an incredible ability to see things in nothing. Like this "time traveler" discovered in an old photo.
But Venus isn't the only victim. Particularly since remember here there is no evidence that the Venus of Willendorf was a portrait of a person. It's not an n=1 situation, it's an n=0 situation. There is no way to prove that someone would have had to have been familiar with excess adiposity in order to create a figurine like that and certainly nothing you can draw from that single figurine that would suggest we should eat a low fat diet!
Another great example of grasping at straws to use art in paleopathology (the study of disease in archeological remains, though this is obviously stupid here since there ARE no remains, just random statues) is Male Genital Representation in Paleolithic Art: Erection and Circumcision Before History.
In this paper the authors suggest that various features of phallic figurines from the paleolithic suggest all sorts of pathologies such as phimosis. Furthermore, the authors saw that they show circumcision was practiced, though he admits reluctantly it they could also be retracted penises. There is a reason this isn't in the Journal of Physical Anthropology, but in Urology instead. Here is some of the diagnostic "evidence"
Why are the weird phallic pieces proof of phimosis but the drawings with giant phalli not proof that people back then had abnormally ginormous penises? Why would you assume any sort of anatomical correctness for these sort of things? Just because you didn't put a foreskin in your art doesn't mean they didn't have them. I can report that in bars in Europe where few men are circumcised, when people draw penises in the bathroom (co-ed bathrooms are rather unpleasant BTW), they look like those in Figure 5.
So yeah, using art to muse about what people were like back then is interesting. Using it to diagnose illness or make inferences about the population is just silly.
Edit: is it true that circumcision is practiced by at least 7 forager groups. Interesting.
I find it quite amusing when people accuse me of having one hunter-gatherer stereotype when it's also clear they hold one themselves. The most popular thing to accuse people of is that they hold the "man the hunter" hypothesis that people ate mostly meat and men provided most of the food. The challenging hypothesis is that humans mostly ate plants and women provided most of the food. The data does not support this very politically correct hypothesis because it plays to popular modern ideas, namely that plants are really good for you and women do all the work and don't get any credit for it. The Ethnographic Atlas is an extensive collection of data on hunter-gatherers and other cultures. In the excellent oldie but goodie Myths About Hunter-Gatherers, the author looks at the data and sees that:
It's perfectly logical omitting equistrians like the Plains indians because any culture using domesticated animals is pastoral, not hunter-gatherer. She notes that some of the "gathering was more important" stuff came from anthropologists who classified fishing as "gathering."
But old myths die hard and I still both of these incorrect ideas bandied around: "man the hunter" and "man the gatherer." The reality is more varied and doesn't really fit either. What about "man the fisher?" Or man the scavenger (luckily the topic of a paper I am writing for my latest anth class)? It's more like "man the opportunist." But either way...it seems to be men bringing home the bacon. Cordain has also done a more famous paper on the topic of hunting vs. gathering, but clearly not famous enough since I still see these myths around and have commenters repeat these myths over and over (and accusing me of not knowing anything about anthropology...).
Earlier on Twitter I circulated an interesting recent paper a commenter pointed me to- Hypogonadism and erectile dysfunction associated with soy product consumption. The paper documents the case of a 19 year old who had type 1 diabetes, but no other health problems. After starting a vegan diet he experienced alarming erectile dysfunction and general loss of libido. Upon examination, low testosterone levels were found. When asked about his habits, he revealed that he had recently switched to a vegan diet: "This diet included a large amount of soy products equalling 360 mg of isoflavones per day. The diet consisted of soy milk, soy cookies (soy crisps), tofu, soy sauce, soy nuts, and soybeans (edamame)." He quit the vegan diet, but it took almost a year for his testosterone levels to normalize (and the normal line should be higher for a young man).
It's funny because professional soy shill (he works for the Soy Board) and (not coincidentally) animal rights activist Mark Messinahas written many articles that male vegan friends of mine have showed me about how soy doesn't feminize men. He even published a review on it in which he concludes "Thus, men can feel confident that making soy a part of their diet will not compromise their virility or reproductive health." This despite the infancy of the science. For example, look at how long these studies are:
And how much soy? For whom? Are their genetic differences in processing isoflavones? Hmm. I can't say that soy is always an issue for men, but like any plant food, it can have powerful hormonal effects that people should be aware of. On the other side of the spectrum is a man who used phytoestrogens to improve his sperm quality and was able get his wife pregnant.
One thing that struck me about the list of foods from the young man is that they are all the processed dreck that Messina and his Soy Board shills want to sell us. They are hyperpalatable and my experience with them is that they are very easy to overeat. I remember buying a box of Tofutti Cuties and eating them all in a single night...
I am not one of those folks who doesn't ever eat soy. I enjoy miso and soy sauce when I eat Japanese food. Like most traditional soy foods, they are very strong and it's hard to eat too much of them. When I was at ag school in Illinois, I had a class that was a series of seminars. One of them was a visit to the food science lab sponsored by the Soy Board. In that lab the lead scientist talked about how they were removing (or overpowering) the natural bitter flavors in soy to make tastier soy foods! Hmm. That bitter taste is what keeps us from eating too much plant poison. I feel bad for vegans who care more about their health than about soy farmers, because the reality is that you CAN do a vegan diet with reasonable levels of soy or no soy at all.
In other news, my spell checker wants to correct edamame into "damned."
I was going to just do one big post on this subject, but the amount of information out there is so extravagant that perhaps I'll do several. I suspect this topic doesn't get much air because well, most bloggers don't want to relate personal anecdotes. And really, there are no really good solutions to this issue.
If you are anything like me, in high school health class you were taught that things were pretty bad for women and then suddenly they invented The Pill and it freed us to enjoy sex without worry.
Like many women I was given the pill before birth control was even on my mind. Doctors routinely give it out to make menstrual cycles "more regular," fix PMS, cure acne, and for other non-birth control reasons.
This troubles me and now that I know better I would make sure that any daughter I have isn't handed the pill so casually. There are so many types of hormonal contraceptives and so many conflicting studies that it's hard to say that the pill is a bad thing. But given how little we still know about human reproduction, I'd rather not take it unless I have to. When I stopped taking it many frustratingly persistent health problems I struggled with went away.
I think because there aren't very many good alternatives for birth control, some of the problems with the pill are swept under the rug. Women deserve to know about them.
So here are some good sources I've been reading:
Some letters from a study on long-term mortality. Here are some good quotes (nulliparous means women who have never had children)
"Deaths increased three times more in “ever” takers under age 30 than in young “never” takers. GP observed “ever” takers had significant increased mortality rates compared with “never” takers for all circulatory diseases, cerebrovascular disease, other circulatory diseases (thrombosis), and violence (perhaps reflecting previously increases in mental illness and marital break ups in “ever” takers). A much vaunted ovarian cancer reduction depended on 14 deaths in “ever” takers and 29 deaths in “never” takers and 75 deaths in each group in the full data set. Whether these women were taking fertility drugs or HRT, which can increase the risk of ovarian cancer, is unknown.2,3"- Dr. Ellen Grant
"Troubling trends of increased morbidity and mortality among OC users v. non-users are also apparent when considering the subset of women who constituted a small minority of users in this study cohort, but who predominate among current users, namely, young nulliparous women."- Dr. Joel Brind
"The results of this large study are really welcome and promising to highlight long term safety of oral pills which are the most effective method of contraception and save many women's lives from complications of unwanted pregnancies-" Dr. Sharma
"It is surprising why the authors did not give greater importance to the fact that such a huge proportion of participants (one third) were lost to follow-up. Usually, a great restrain is needed when interpreting a cohort study attaining a retention rate lower than 80%."- Dr. Miguel A. Martinez-Gonzalez
"It is now surely inconceivable that any medical scientist who has some understanding of basic mechanisms could believe that widespread hormone use, especially of progesterones, is not a major health problem."- Dr. Ellen Grant
Here is among the most interesting letters:
Hannahford et al. (2010) report convincing evidence for reduction in mortality from several forms of cancer and other disease in women who have used oral contraception compared to never users. However, they also find a higher rate of violent death among ever users, and that the rate of violent death increases with longer duration of oral contraceptive use, but they are unable to explain these intriguing results. I suggest that recent evolutionary insights into human partner choice may provide a clue.
There is evidence that use of oral contraception alters women’s baseline preferences for men[2,3] such that pill users prefer men who are relatively similar to themselves at loci in the major histocompatibility complex (MHC). One consequence of being partnered with relatively MHC-similar men is that such women express lower sexual responsivity toward their long-term partner compared with women in relatively MHC-dissimilar couples, reject sexual advances from their partner more frequently, and report having had more extra-pair partners. Other evidence points to MHC- similar couples being more likely to experience problems conceiving children, and having less healthy children due to lower MHC-heterozygosity. Cumulatively, these effects could have real impact on the quality of spousal relationships[3,5].
It is not unreasonable to suspect that such effects could also influence rates of intimate partner violence. This is the most common cause of nonfatal injury among women and accounts for more than a third of women murdered in the US. Furthermore, ex-partners are a key risk factor, which could further emphasise the risk for pill users if the behavioural effects of pill use ultimately influence rates of marital breakdown[3,5].- Dr. S. Craig Roberts
As you can see there is still a bit of a debate on how exactly hormonal contraceptives impact women's long-term health. A debate I was totally unaware of when I was on them...
And more and more stuff still comes out every year showing unintended effects. An interesting, but inconclusive study last year found that hormonal contraception can change a woman's brain structure. I could definitely write separate posts on how the pill effects nutrition, future fertility, bone density, inflammation, heart disease risk, hypertension, libido, mood, and that's the tip of the iceberg. I can't promise a series, but this is a topic that definitely interests me.
Context and Variation has a good post about The Pill from an anthropological perspective.
The second health issue I want to mention is the potential increase in systemic inflammation with the use of hormonal contraceptives (one of my other undergraduates, Katherine Tribble, found this article for our lab's weekly journal club). Morin-Papunen et al (2008) looked at women at thirty one years of age in the Northern Finland Birth Cohort, born in 1966. They grouped these women into levonorgestrel-releasing intrauterine device (IUD) users, oral contraceptive users, and no hormonal contraception use. Morin-Papunen et al (2008) found oral contraceptive usage was correlated with increased C-reactive protein concentrations -- this is a biomarker for inflammation that is associated with cardiovascular disease. Compared to IUD users, oral contraceptive users also had more insulin resistance, higher blood pressure, raised lipids and insulin levels, despite having a smaller waist and lower waist-hip ratio (a larger waist or higher waist-hip ratio is often associated with these results). Further, most of these results actually strengthened when factors like BMI, household income, and alcohol consumption were controlled for. Another interesting point, third generation hormonal contraceptives, which are lower concentrations of synthetic hormones than the second generation, actually had higher serum levels of insulin, CRP, total cholesterol and other lipids, compared to users of second generation contraceptives.
Based on my own research, I think it's not a good idea to use The Pill for anything other than birth control unless all other options have been explored. As birth control it is the most effective, which leaves women who don't do well on it or who would prefer to take a precautionary approach with some tough choices. There is some evidence that non-oral methods like the Nuvaring are better, though actually there are some disturbing studies on the patch and Depo. Women in marriages/long-term relationships for whom a pregnancy wouldn't be the worst thing might want to explore fertility charting (this isn't your mom's method, significant research and improvement has been done on this method in the last decade) or withdrawal (possibly just as effective as condoms).
I think an issue is that it's considered silly to think about children in your twenties. But just because you'll change in the future doesn't mean you shouldn't think about it at all. If you are trying to live close to the species optimum as possible in the modern world, you will probably make different choices.
I said I'd go to bed, but then I read something interesting. Lately there has been some discussion in the comments here about what level of body fat is healthy for women. Is it healthy for women to be as lean as men should be (below 18% body fat)? Some authors say yes. After all, don't women in third world refugee camps have babies all the time?
Turns out it's more complex than that. Ancient Bodies, Modern Lives is my go-to reference on this sort of thing and lo and behold it had some answers on this matter.
To a great extent, reproductive hormone levels are set during development and reflect resource availability while a girl is growing.As we will see with regard to fetal development, a maturing system (the reproductive system in this case) reads cues about the environment to assess future conditions and adjusts levels of hormones and other components of the system to match the expected conditions. If a girl develops in a health-rich environment, her system "expects" that environment to be stable, but if she experiences short-term deprivation fo food, for example, her reproductive system may down regulate to wait for the expected better times.
Wenda mentions some rare examples of famines in first world countries, like the Dutch famine in WWII, where fertility levels completely crashed. So it's theorized that each woman has a "set point" established while growing up that determines her body's response to food intake.
Ammenorhea is a complex condition. Lots of long-distance runners suffer from it(which makes me doubt that women participating in persistence hunts was ever part of our evolutionary history)...but others don't. It sounds like a cliche, but everyone is different. For exercise-induced ammenorhea, it's not just body fat that's a factor, but cortisol and probably quite a few other hormones.
I would note that many advocates of low body fat for women are men. My own opinion is that this is foolish and will lead women to disordered eating. The only body fat that you want to avoid is visceral fat. I guess if you don't want to have children and care mostly about being super lean you can do that...but don't pretend it's healthy or natural.
Lassek and Gaulin also argue that hip and buttocks fat are the primary sources of fatty acids that are passed from the mother to the fetus during gestation and the infant during lactation. These long-chain polyunsaturated fatty acids play a major role in brain development. Thus, they argue, hip and buttocks body fat does not just signal overall energy availability for pregnancy, but also signals that the essential fatty acids for brain development are in sufficient supply. Does hip and buttock fat correlate with cognitive abilities? IN an examination of the third NHANES study database, Lassak and Gaulin found that high amounts of hip and buttocks fat relative to waist size (a low waist-hip ratio) was predictive of women's own and their offspring's cognitive performance. They refer to this fat as "a privileged store of neurodevelopmental resources.
I think other people refer to it as "my humps"
Edit: some commenters got the idea that this is about being "fat", which is it not. I mention that visceral fat is a highly unhealthy possession, and it is. Ideally a woman should have a relatively flat belly (unless she is pregnant), but not worry about ample hips, buttocks, or breasts.
Don at Primal Wisdom recently had a post on hormone levels in beef, which was really about whether or not hormone-treated factory farmed meat is unsafe*, but I was more interested in hormone levels in general.
I once had a native African explain to me that among her people, they have a taboo against hunting female animals. This taboo makes a lot of sense for a tribe dependent on hunting. If you kill a female, you are eliminating a bunch of potential offspring at the same time; while killing a few bulls will have essentially no effect on the fecundity of the herd.
So hunters would have preferred eating bulls to cows, and in Europe still today some producers raise bulls. Similarly, in the U.S. we get most of our beef from steer—neutered bulls—while we save the cows for calving and milk production.
Bulls and steer differ hormonally. Bull meat samples tested by Fritsche and Steinhart  contained medians of 0.34 mg/kg testosterone and 0.32 mg/kg epitestosterone, while steer meat samples (from unsupplemented steers) contain medians of 0.01 mg/kg testosterone and 0.12 mg/kg epitestosterone. Bull meat had up to 1.05 mg/kg testosterone. Thus, bull meat contains a median of 34 times more testosterone and more than twice as much epitestosterone than steer meat; and bull meat might have up to 105 times as much testosterone as a steer.
I've also read about these taboos. A long time ago I took a class on African agricultural economics and did a paper on how food taboos protected resources. Many cultures have taboos against killing young, lactating, pregnant, or female animals. It makes sense.
But maybe our beef these days doesn't have enough testosterone because we are consuming steers rather than virile males? As Tim Ferriss says in Four Hour Body "The sperm counts of men in the United States and 20 other industrialized countries have been falling since 1942 at a rate of roughly 1% per year in healthy males."
As an aside, many cultures have male virility rituals which involved the ingestion of animal penises and testicles or human seminal fluid.
It's an interesting thought I'll just throw out there, which came to mind when Ulla Kjarval tweeted me that she thought us paleos would be most interested in her father's bull meat for sale. Her father, Ingimundur Kjarval, has a grass-based farm and blogs at healthymeat.org. If you are in or near NYC you can vote for Meatshare to buy it.
* I think we don't know and even if wild animals have high hormone levels, animals treated with the synthetic stuff still might be different. I prefer to take the precautionary approach. And there are other reasons not to eat factory farmed beef, though I think it's a better choice that factory chicken or pork because it spends some time on grass.
So far the best book about how evolution has shaped women's bodies. Chock full of interesting info.
Chris Masterjohn pointed out that my last semen post pointed towards a biological bolster for monogamy in this modern age. Here is another. I'm sorry but this post is less fun than the last one about semen, but I promise another one that is less alarming in the future, though I have a post in the queue on birth control that's rather unfun.
So humans are one of the few species that engages in non-reproductive sex. We have sex when the woman isn't pregnant (and between people who can't get pregnant), but also when the woman is already pregnant. Biologically this seems a little pointless. But this paper(PDF) sheds light on reasons why it might be beneficial, as long as the semen is from the man who is the father of the baby.
Preeclampsia is one of the few true dangers to pregnant women in the first world. It causes severe hypertension and can cause the loss of the baby, the mother, or both. The death rate is 790 maternal deaths per 100,000 live births.
The prospective causes of it are complex and I'm not going to talk about all of them. Evolutionarily some scientists speculate it is caused by the nutritional hunger of a developing baby's brain, which is very high compared to our forebearer species. Other species don't get it at the fairly high rate we do. The paper discusses the fact that evolutionarily speaking, paternal investment improves survivability. Sex at Dawn argues against this using examples of some modern tribal societies where children are raised communally, but it's impossible to know whether this was the state of things in the paleolithic and either way there is good evidence that evolution has continued since then.
Several studies, particularly on babies conceived with donor semen, show higher risk of preeclampsia in pregnancies with non-paternal semen exposure. If you have a second pregnancy and the father is different from the first, it seems risk for preeclampsia is also higher. Interestingly, exposure to consistent and familiar semen (a la in a monogamous relationship) seems to increase odds of getting pregnant.
What about just not having sex during pregnancy? Don't do that! That increases risk of preeclampsia as well! You might as well have some oral sex, as that is also shown to reduce odds of preeclampsia in some studies.
Why does this happen? Perhaps it's an evolutionary response to the dangers of carrying an unwanted pregnancy (from a rape for example) or perhaps to the benefits of paternal investment. Either way, it's very interesting and supports the idea that if you want to have a healthy baby it might be better to be married or in a monogamous relationship.
Now that I have just written a rather dry post, I thought I'd see what's up with my Google Analytics. Some Google searches that have brought people to this site are pretty funny:
"obligatory sex activity"
"paleo sex how often"
Well I much say that it's important for paleo dieters to have sex every day. It's obligatory because it's rather good for you. I totally apologize to the person who searched for "negative effects of men being pushed into having sex" for this post because it might cause more of that sort of thing.
Now that I have journal access again, I've been reading some interesting papers. I'm surprised this one was published, because I'm sure it will lead to some awkward pickup lines at campus bars.
Dude: Feeling down?
Girl: Yeah, just a bit.
Dude: Well I just read a paper in Archives of Sexual Behavior called Does Semen Have Antidepressant Properties? The p-value is pretty high. You might want to try it out.
Yes, I'm serious, this is a real paper. It relies on surveys of sexual behavior and depressive behavior in co-eds in Albany. That's one strike against it already, since people in Albany are known to be depressed because they live in Albany, despite the fact that 87% of the women were having sex. But more seriously, surveys themselves are rather suspect. I remember quite vividly lying on surveys in health class in high school, though I imagine they threw mine out because I said I did heroin 20 times a day.
The researchers cited evidence that hormones in semen are absorbed through the vaginal wall and could possibly influence behavior. Some of these hormones include testosterone, estrogen, follicle stimulating hormone and luteinizing hormone, prolactin, and a number of different prostaglandins. The vaginal cells are surprisingly good at absorbing these things. The researchers speculated that this might affect women's mood.
Based on the survey, it seems women engaging in unprotected sex were less depressed. Women who used condoms were just as depressed as women not having sex at all. The researchers admitted that the data was preliminary and correlational and call for further studies.
The researchers noted that there could be many explanations. Women who didn't use condoms had more sex, which the researchers said might make them less depressed (lol). They also said that given the risks of unprotected sex, that it might be more likely such women were in long-term monogamous relationships. When I wrote about Sex at Dawn, which posits that humans are "naturally promiscious" I noted that this doesn't really provide a solution for having a satisfying modern sex life. I think this paper highlights a benefit mostly enjoyed in long term monogamous relationships in our modern society where sex is fairly dangerous.
They regrettably omitted what is totally obvious to anyone who has ever used a condom already knows: that they suck and no one likes them.They also omitted discussion of other ways in which semen might enter a woman's system.
Other factors notably absent include whether or not the women practiced birth control and which type, which can have a huge influence on women's moods for better or worse.
What follows in this journal are two hilarious letters. One is Greater Frequency of Penile–Vaginal Intercourse Without Condoms is Associated with Better Mental Health and the other is Sparse Evidence for the Association between Lack of Condom Use and Better Mental Health, a killjoy which accurately takes down the survey accuracy of the studies cited. I do think that given all the stuff that's in semen, that it has more complex effects than we give it credit for. In hunter-gatherer societies women are often exposed to large amounts of it, and sometimes men are too.* And it's an interesting topic that I hope to post more about. Some other aspects that I've researched include the declining quality of semen in modern times.
* See Ritualized Homosexuality in Melanesia (VERY VERY NSFW), one part of the Pacific diet that is not often written about...