New research from the University of Granada found that stress could help determine sex.
- A new study found that women with elevated stress before, during, and after conception are twice as likely to deliver a girl.
- One factor could be that sperm carrying an X chromosome are better equipped to reach the egg under adverse conditions.
- Another factor could be miscarriage of male fetuses during times of stress.
Stress in the modern world is generally viewed as a hindrance to a healthy life.
Indeed, excess stress is associated with numerous problems, including cardiovascular disease, high blood pressure, insomnia, depression, obesity, and other conditions. While the physiological mechanisms associated with stress can be beneficial, as Kelly McGonigal points out in The Upside of Stress, the modern wellness industry is built on the foundation of stress relief.
The effects of stress on pregnant mothers is another longstanding area of research. For example, what potential negative effects do elevated levels of cortisol, epinephrine, and norepinephrine have on fetal development?
A new study, published in the Journal of Developmental Origins of Health and Disease, investigated a very specific aspect of stress on fetuses: does it affect sex? Their findings reveal that women with elevated stress are twice as likely to give birth to a girl.
For this research, the University of Granada scientists recorded the stress levels of 108 women before, during, and after conception. By testing cortisol concentration in their hair and subjecting the women to a variety of psychological tests, the researchers discovered that stress indeed influences sex. Specifically, stress made women twice as likely to deliver a baby girl.
The team points out that their research is consistent with other research that used saliva to show that stress resulted in a decreased likelihood of delivering a boy.
Maria Isabel Peralta RamírezPhoto courtesy of University of Granada
Lead author María Isabel Peralta Ramírez, a researcher at the UGR's Department of Personality, Evaluation and Psychological Treatment, says that prior research focused on stress levels leading up to and after birth. She was interested in stress's impact leading up to conception. She says:
"Specifically, our research group has shown in numerous publications how psychological stress in the mother generates a greater number of psychopathological symptoms during pregnancy: postpartum depression, a greater likelihood of assisted delivery, an increase in the time taken for lactation to commence (lactogenesis), or inferior neurodevelopment of the baby six months after birth."
While no conclusive evidence has been rendered, the research team believes that activation of the mother's endogenous stress system during conception sets the concentration of sex hormones that will be carried throughout development. As the team writes, "there is evidence that testosterone functions as a mechanism when determining the baby's sex, since the greater the prenatal stress levels, the higher the levels of female testosterone." Levels of paternal stress were not factored into this research.
Previous studies show that sperm carrying an X chromosome are better equipped to reach the egg under adverse conditions than sperm carrying the Y chromosome. Y fetuses also mature slowly and are more likely to produce complications than X fetuses. Peralta also noted that there might be more aborted male fetuses during times of early maternal stress, which would favor more girls being born under such circumstances.
In the future, Peralta and her team say an investigation into aborted fetuses should be undertaken. Right now, the research was limited to a small sample size that did not factor in a number of elements. Still, the team concludes, "the research presented here is pioneering to the extent that it links prenatal stress to the sex of newborns."
Stay in touch with Derek on Twitter and Facebook. His most recent book is "Hero's Dose: The Case For Psychedelics in Ritual and Therapy."
New research shows that experiencing an opposite-sex body in virtual reality impacted the subject's gender identity.
- Scientists find that experiencing an opposite-sex body can affect a person's gender identity.
- A new study utilized virtual reality to get subjects to feel like they had a stranger's body.
- The researchers found that people's sense of their own gender became more balanced after the experiments.
Is associating with a certain gender more of a flexible sense than hardwired biological fact? A new study shows that people who were put under the illusion of having an opposite-sex body developed a more equal understanding, with fewer stereotypes, of both male and female aspects.
In their paper, the scientists defined gender identity as "a collection of thoughts and feelings about one's own gender, which may or may not correspond to the sex assigned at birth." To probe this, they designed three experiments using virtual reality that allowed people to experience what it's like to have a body they weren't born with.
The experiments, led by Pawel Tacikowski of Karolinska Institutet in Sweden, involved a relatively large sample of 140 people. One of the experiments had participants wearing a head-mounted display that was playing a first-person POV video of either a male or female body. The participants had to watch the stranger's body being touched while the same kind of action, on the same part, was being performed to their body. The synchronized nature of the touching created the illusion of another person's body being their own.
One of the changed conditions had the stranger's body appear to be threatened with a knife. Other control conditions had the touches being asynchronous, disrupting the illusion. In all the cases, the subjects had to tell the scientists how masculine or feminine they perceived themselves. The experiments showed that the participants felt more connected to another person's body when the conditions were synchronized. Both females and males reported feeling less identification with their own gender during such experiences.
Credit: Tacikowski / Fust/ Ehrsson / Scientific Reports.
In experiment (a), subjects wore a head-mounted display in which a body of an unknown male or female was shown from a first-person perspective (with the participant's actual body out of view). In part (b), participants had to rate the illusion after every interaction to assess the degree of feeling that the stranger's body was their own.
"We found that even a brief transformation of one's own perceived bodily sex dynamically updated the subjective, implicit, and personality-related aspects of the sense of own gender and made these aspects more balanced across male and female categories," write the scientists, adding "The fluidity of gender identity that we report here extends previous knowledge by demonstrating that the link between own body perception and the sense of own gender is dynamic, robust, and direct."
Another experiment utilized the Implicit Association Test (IAT) to find that the implicit gender biases of the subjects became more balanced during the illusion of having the body of the opposite sex. The third test demonstrated that the illusion also affected explicit gender beliefs, with the participants more equally ranking both masculine and feminine traits.
Current gender theories, as outlined in the study, have moved away from positioning gender identity as a strict "male-female dichotomy." Instead, the scientists say, the prevailing view is that gender is derived individually from a variety of associations with both genders, as well as from personal genetics, hormones, patterns of behavior and social life. There is also the understanding that the sense of your own gender is determined by your beliefs about males and females overall.
Check out the study "Fluidity of gender identity induced by illusory body-sex change" in the journal Scientific Reports.
A study of the Mosuo women, known for their matriarchy, suggests that gender roles can influence our health outcomes.
- An isolated ethnic group in China maintains a matriarchal society, much to the benefit of their health.
- The Mosuo women were not only healthier than women living under patriarchy, but were healthier than the men too.
- The findings support the idea that having a degree of autonomy and resource control is good for your health
Every debate about what is innate to humans and what is learned from society runs into the problem of having to rely on humans who live in some kind of society for reference. Claims about human nature can easily be repackaged as claims about people living in similar cultures and vice versa.
Current debates over sex, gender, and what behaviors are biologically influenced fall into this category. Claims that masculinity and femininity are biologically fixed often point to their seeming universality as evidence. However, as mentioned, these claims often rely on people raised in cultures that encourage or discourage people from taking on those traits. It is a bit of a chicken and egg problem.
One way to try and get around these problems is to find a culture that is markedly different from others. A new study on women's health has taken this route; it discovered that granting women autonomy typically given only to men leads to better health outcomes.
The Kingdom of Women
The Mosuo people are an ethnic group that lives in the Yunnan and Sichuan regions of China, next door to Tibet. Long isolated from other parts of China—and insulated against the occasional upheavals that impacted other cultures—they continue to maintain cultural institutions commonly described as matriarchal or matrilineal.
Children take the name of their mother's family, who they live with all their lives. Households are run by matriarchs, often the grandmother, and inheritance goes from mother to daughter. The matriarch makes all major household decisions, including financial ones, and women do work often doled out to men in other cultures.
They are also known to practice a unique form of marriage known as a "walking marriage." In this system, a couple decides to carry on a relationship by mutual consent. They do not live together, remaining in the homes of their respective families. The man, instead, "walks" over to the woman's house for romantic rendezvous. Men have to return home by sunrise.
The relationship is carried on for as long as both parties want but carries no social or economic obligations. It is ended at any time with little difficulty. Many people often confuse this with promiscuity, but most anthropologists report it as a kind of serial monogamy, and many relationships that take this form are long term. Any children resulting from these marriages are raised by the mother's family, though the father may play a role as agreed upon by all involved. Typically, the child's uncles will play the role of father figure.
It is worth noting that men do have some power in this society; they are in charge of all things death-related, including funerals and the killing of animals. They also have some political power, though women often have most of it.
Cases like these are common among matriarchal societies, with men retaining some measure of control over their lives even if they aren't at the top often unknown to women in patriarchal societies. A variety of sources indicate that the men in this society, who are well aware of the alternatives, are often content with their situation. Mosuo villages with patrilineal traditions also exist.
Even with these caveats, it is fair to say that the women of the Mosuo are highly autonomous and have a long history of personal freedom beyond that which is known to women in many other cultures.
Medical considerations of matriarchy
Most of you will know that women tend to outlive men. Fewer of you will know that women tend to have higher morbidity than men do in spite of this.
Two manifestations of this are that women tend to have higher blood pressure than men after reaching post-reproductive age and that women of all ages tend to experience more inflammation than men. Both of these are important markers of long-term health and are commonly associated with other serious conditions.
While these issues have often been calked up to biology, a team of researchers led by Adam Reynolds of the University of New Mexico set out to see if they also existed in Mosuo society. The team recorded health measures in Mosuo individuals living in either a matrilineal or patrilineal society and compared them using statistical methods. The findings have been published in the Proceedings of the National Academy of Sciences.
Levels of C-reactive protein (CRP), a biomarker that can indicate the presence of inflammation, were measured in the blood of 371 Mosuo participants. A mere 3.6 percent of the women living in the matriarchal areas were found to suffer from high inflammation levels unrelated to other conditions. In the patrilineal communities, the prevalence of chronic inflammation in women was 8.3 percent.
Blood pressure tests showed similar results after nearly a thousand people were tested. Of the women living in matrilineal areas, only 25.6 percent had hypertension. A third of women in the comparison areas had the condition.
In a surprising find, not only did the Mosuo women living in the areas where they have control over their lives enjoy lower rates of these conditions than other women, they are healthier than their men as well. Mosuo men living in the matriarchal areas tested for high levels of CRP at double the rate of the women. They also had more hypertension, though the rate was only a slightly higher 27.8 percent.
Now, the men don't suddenly all have high blood pressure because they don't run everything. They have high blood pressure at a rate of only one percent higher than those from the patrilineal culture. If there is an adverse health effect for them caused by living in a matriarchal society, it isn't much of one.
It turns out autonomy might be good for you
Speaking to Inverse, senior author Siobhán Mary Mattison explained their interpretation of the findings:
"Women in these matrilineal communities have a great deal of autonomy in decision-making and excellent social support. Given that women tend to be at greater risk of chronic disease worldwide, the fact that they actually do better than men in this realm of health is telling."
The other authors of the study agree. They conclude that:
"Our data provide partial support for the hypothesis that the effect of matriliny on women's health is associated with increased autonomy and resource control... While patriliny has been linked to reduced autonomy and resource access for women, we demonstrate that these inequalities can have tangible biological effects that contribute to gender disparities in health."
They further note that being head of the household is inversely associated with elevated CRP levels, suggesting that autonomy grants a "protective" effect against inflammation. Lastly, they suggest that the impact of culture, resource control, and autonomy on health all be given further study to capitalize on these findings.
These interpretations would be in line with other findings that suggest racism, which similarly limits human autonomy, is terrible for people's health. The stresses of racism are linked to babies with low birth weight, heart disease, and poorer health outcomes.
While a study on a single, small, isolated group of people isn't going to be the final word on the subject, it does point towards the idea that our health is impacted by our culture and the limitations it puts on us. As we consider ways to improve the world and better understand ourselves, this study and the example of the Mosuo more generally, must be remembered.
Turns out gender assumptions have been going on for quite some time.
- A recent archaeological dig in the Peruvian mountains uncovered evidence of ancient female big-game hunters.
- This adds to a growing consensus that women played a much bigger role in hunting than previously assumed.
- Gender assumptions are a constant throughout history, with culture often playing a more important role than biology.
You've likely heard it like this: for most of history, women foraged, secured water, and partook in minor agriculture while men went out to hunt. Even if this was the end of the story, women still provided an inordinate amount of calories for the tribe, as fruits, vegetables, and nuts accounted for the bulk of sustenance.
As with many myths, this longstanding story might not be completely accurate. Thanks to recent archaeological findings in Peru's Andes Mountains, published in the journal Science Advances, up to half the women in mobile groups in the Americas were big-game hunters.
University of California, Davis archaeologist Randall Haas started shifting his view of ancient hunting practices in 2018 while leading his crew 13,000 feet above sea level in Wilamay Patxja. Upon uncovering the remains, he automatically assumed one body was male due to the proximity of weaponry.
He was wrong.
The team unearthed a total of over 20,000 artifacts, including the remains of six bodies in five burial pits. One pit, which contained a teenage woman, included a toolkit with spearpoints and shafts. Tools for dissecting game were also discovered. In total, 24 stone tools were unearthed, including projectile points for killing large game, heavy rocks for stripping hides and cracking bones, and red ocher to preserve hides.
Previously, such tools were thought to be used for cutting or scraping when discovered near female remains. Haas says we need to rethink that approach, which is likely the result of modern bias. Buried near these pits were the remains of Andean deer and vicuña, two commonly hunted animals in Peru.
Haas's group then reviewed the remains of 429 bodies spread over 107 sites in the Americas. These individuals lived between 6,000 and 12,500 years ago. Big-game hunting tools were buried with 11 women and 16 men. The Wilamay Patxja dig is not an outlier.
Credit: Randall Haas, University of California, Davis
Why Female Gladiators Were Polarizing Figures in Ancient Rome
Extrapolating from the most recent dataset, Haas estimates that between 30-50 percent of big-game hunters were women. This doesn't imply that it's a global phenomenon, although female warriors were recently identified in California, dating back roughly 5,000 years. Likewise, women warriors were discovered in Mongolia 1,500 years ago and in Scandinavia about a millennium ago.
Researchers say these findings challenge our understanding of gender identities. Modern analysis can discover the biological sex of these individuals, though we cannot make assumptions about the role of men and women by current standards. As University of Miami archaeologist, Pamela Geller says,
"With few exceptions, the researchers who study hunting and gathering groups—regardless of which continent they work on—presume that a sexual division of labor was universal and rigid. And because it is commonsensical, they then have a hard time explaining why female-bodied individuals also bear the skeletal markers of hunting or have hunting tool kits as grave goods."
There's always the possibility that hunting tools were ritualistically buried alongside varied members of the tribe, including women. Yet we also have to remember that there were no supermarkets on the savanna. Tribal life was an all-hands-on-deck affair. Female hunters should surprise us no more than stay-at-home dads today. Societies are fluid dependent on circumstances, and the ancient world provided challenges we can only dream of today.
Stay in touch with Derek on Twitter and Facebook. His new book is "Hero's Dose: The Case For Psychedelics in Ritual and Therapy."
The color of toys has a much deeper effect on children than some parents may realize.
- The idea that blue is for boys and pink is for girls plays out in gender reveals and in the toy aisle, but where does it come from and what limits is it potentially placing on children?
- Lisa Selin Davis traces the gendering of toys and other objects back to the 1920s and explains how, over time, these marketing strategies were falsely conflated with biological traits.
- The "pink-blue divide" affects boys and girls on a psychological level. For example, psychologists discovered that when girls exit their intense 'pink princess' phase between ages 3-6 and move into a tomboy 'I hate pink' phase at age 6-8 "that is actually a moment of girls realizing that what's marked as feminine is devalued and so they're distancing themselves from it to prop themselves up higher on the ladder," says Selin Davis.