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."
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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."
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.
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
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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.
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Stay in touch with Derek on Twitter and Facebook. His new book is "Hero's Dose: The Case For Psychedelics in Ritual and Therapy."
