Human childbirth is a relatively painful and complicated process in the animal kingdom.
Unlike other primates that are able to give birth unassisted, human mothers usually need help from their family or community to deliver a baby. Even with help, mothers and infants face a small chance of death during childbirth, especially in regions with limited access to healthcare, like Sub-Saharan Africa.
One reason human childbirth is dangerous is the "obstetrical dilemma." This dilemma describes what seems to be an anatomical contradiction: Human infants have large heads, but their mothers have small birth canals.
To pass through the birth canal, human infants have to perform a series of twists and turns, a process called rotational birth. (Human infants also have fontanels, commonly referred to as soft spots, which help them better squeeze through the birth canal.)
It begs the question: Why hasn't evolution made childbirth easier on humans?
Evolutionary trade-offs
A study recently published in Proceedings of the National Academy of Sciences proposes that human childbirth is difficult because of evolutionary trade-offs that ultimately help protect organs in the body.
The main trade-off for women centers on the pelvic floor, which is a group of muscles that stretches from the pubic bone to the tailbone. These muscles help stabilize the spine, support the womb, and control bladder and bowel functions. The pelvic floor also stretches during childbirth, allowing the baby to pass more easily through the birth canal.
A medical illustration depicting the female pelvic muscles.
A medical illustration depicting the female pelvic muscles.Credit: BruceBlaus via Wikipedia and licensed under CC BY-SA 4.0
Some researchers have proposed that a larger pelvic floor would make childbirth easier for women. But others have countered that a larger pelvic floor would actually be more vulnerable to deformation and could lead to disorders, including incontinence and organs dropping from their normal positions (known as prolapse).
Known as the "pelvic floor hypothesis," this idea has been difficult to test. In the current study, a team of researchers from the University of Texas and University of Vienna used computer models to test how increasing the size and thickness of the pelvic floor might affect women, both in general and during childbirth.
To test the models, the team used finite element analysis. This method, more commonly used in engineering projects, uses mathematics to test how structures would likely react to real-world forces, such as vibration, heat, fluid flow, and pressure. After testing a wide range of pelvic floor sizes and thicknesses, the results suggested that the pelvic floor hypothesis is correct.
"We found that thicker pelvic floors would require quite a bit higher intra-abdominal pressures than humans are capable of generating to stretch during childbirth," Nicole Grunstra, an affiliated researcher at the University of Vienna's Unit for Theoretical Biology in the Department of Evolutionary Biology, told UT News.
"Being unable to push the baby through a resistant pelvic floor would equally complicate childbirth, despite the extra space available in the birth canal, and so pelvic floor thickness appears to be another evolutionary 'compromise,' in addition to the size of the birth canal."
The results highlight how evolution has helped us achieve remarkable anatomical balance.
"Although this dimension has made childbirth more difficult, we have evolved to a point where the pelvic floor and canal can balance supporting internal organs while also facilitating childbirth and making it as easy as possible," lead study author Krishna Kumar told UT News.
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."
There's more gender equality in Western societies today than in the past. Inequalities still exist, of course, but research shows a general uptrend in women joining and rising within the workforce, obtaining degrees, and earning more money. The social expectations of men and women also seemed to have changed; this is harder to measure empirically, but it seems safe to say that our ideas about gender roles are more fluid today than they were, in say, the 1950s.
So, have these changes affected a crucial part of children's development: play? More specifically, as gender roles have become more fluid, have children's preferences toward gender-typed toys become more fluid, too?
The short answer seems to be no. For decades, studies have shown that boys and girls generally prefer playing with toys typically associated with their biological sex: toy trucks for boys and dolls for girls, to give a rough example.
These results have remained remarkably stable over the past 50 years, according to a 2020 meta-analysis of research on gender differences in toy preferences. Published in Archives of Sexual Behavior and titled "The Magnitude of Children's Gender‐Related Toy Interests Has Remained Stable Over 50 Years of Research," the analysis examined 75 previous studies, 113 effect sizes, and a range of toy preference measurements.
No matter what society wants, it's worth noting that there seems to be some biological drivers behind children's preferences for gender-typical toys.
The authors, Jac T. M. Davis and Melissa Hines, found "a broad consistency of results across the large body of research on children's gender-related toy preferences: children showed large and reliable preferences for toys that were related to their own gender. Thus, according to our review, gender-related toy preferences may be considered a well-established finding."
A letter to the editor in the same journal sought to challenge these findings in a separate analysis, which concluded that children actually spend less time playing with gender-typical toys these days.
The authors of that analysis speculated that the reason for this decline "might reflect social pressures in recent times for children to be less gender-typical in their behavior." In other words, the decline stems from parents wanting to be more in line with progressive ideas about gender fluidity.
However, Davis and Hines disagreed, proposing that the supposed decline appeared in the analysis only because of the specific methodology employed by the researchers. What's more, they noted that toy advertisers have been using more gender stereotypes to boost sales in recent decades—a finding that potentially complicates the claim that social pressures are causing kids to spend less time playing with gender-typical toys.
Davis and Hines concluded:
"It may be tempting to think that social changes over time might be reducing children's play with gender-related toys, given arguments that play with a broader set of toys would be beneficial for both boys and girls. Unfortunately, however, broad change in the social roles of men and women do not seem to have influenced children's toy choices, perhaps because they have been counteracted by stronger marketing of different toys to girls and boys over recent time. If society wants girls and boys to play with the full range of toys, more targeted action is probably required."
Little boy playing mathematics wooden toy at nurseryCredit: Rawpixel.com via Adobe Stock
Why are we so concerned about which toys kids play with?
But does society really want kids to play with less gender-typical toys? Some research suggests the answer is yes. A 2017 survey from Pew Research Center found that a majority of Americans considered it a "somewhat or very good thing" to steer kids toward toys and activities traditionally associated with the opposite gender (though respondents were less enthusiastic about doing so for boys than girls).
Encouraging kids to play with a wider range of toys could yield benefits. For example, a 2020 study published in Frontiers in Human Neuroscience found that when both boys and girls play with dolls, they experience heightened activation within brain regions associated with empathy and perspective-taking.
But no matter what society wants, it's worth noting that there seem to be some biological drivers behind children's preferences for gender-typical toys.
For example, studies have shown that babies tend to prefer toys oriented to their own gender, a finding that suggests their preference is innate because they're in the pre-socialization stage of development. Supporting that argument are studies showing that baby monkeys also display gender-typical toy preferences.
Still, it's easy to see how social pressures might affect kids' toy preferences as they grow up. So, the question of why kids prefer the toys that they do likely boils down to a familiar answer: a tangled mix of environmental and biological factors.
"It would be extreme to claim zero influence of biology on gender differences in toy choices, and the research community is still divided on how important biology and social factors are," Davis told Big Think.
In a scathing indictment of the growing influence of money in the private school educational system—and therefore on education, opportunity, and social mobility in America—The Atlantic's Caitlin Flanagan investigates the increasingly troublesome trend of parental involvement in their children's schooling. She points out an anecdotal instance when, as a private school teacher, she butted heads with the same parents twice after giving their child the unforgivable grade of an A-.
One of those irate phone calls came in less than 10 minutes after handing said student their creative writing paper. This meant they left the classroom and bolted straight to the school's pay phone to complain—this was the 1990s, after all. The parents immediately phoned the school. Back then, the school had her back; today, parents yield much more influence, often in the form of endowments.
Flanagan's article highlights two important questions beyond the unyielding influence of money on education: How involved should parents be in their children's education? And what is the emotional result of too much intervention on the child?
A new study, published in the Journal of Family Psychology, attempts to answer both of those questions. Led by Stanford Graduate School of Education Associate Professor Jelena Obradović, the study finds that while it's important for parents to be involved, too much direction and influence can be counterproductive.Why helicopter parenting backfires on kids | Heather Heying | Big Think
For this study, researchers watched videos of parental behavior around their kindergarten-age children. A total of 102 children, ages four to six, were brought into the Stanford lab by their primary caregivers. The children were tasked to clean up toys, learn new games, and discuss problems. The researchers timed the length of their interactions with caregivers, such as how much direction the parents gave them when trying to solve a novel puzzle.
The results were clear.
"The children of parents who more often stepped in to provide instructions, corrections or suggestions or to ask questions – despite the children being appropriately on task – displayed more difficulty regulating their behavior and emotions at other times. These children also performed worse on tasks that measured delayed gratification and other executive functions, skills associated with impulse control and the ability to shift between competing demands for their attention."
Given the laboratory conditions—parents knew they were being watched—Obradović and team noticed that parents did not yell or check their phones. How realistic this is for such a large cohort is difficult to gauge. The team was looking for "parental over-engagement," the tendency for parents to intervene too often and not allow their children to figure things out for themselves.
Credit: Monkey Business / Adobe Stock
Of course, helping children is important as well. The team notes that aiding a child while they work on a new puzzle helps with cognitive development and independence. Striking a balance between lending a hand and letting the child struggle is important. As Obradović states, "there is a lot of variability within those averages, and our goal was to discover more subtle differences among parents who are generally doing fine."
This research is especially pertinent during the pandemic as parents and children are interacting more than ever. The overall message: if you're going to fly a helicopter, only descend when necessary.
This advice is critical for an educational system that, as Flanagan points out, is skewed to favor children from wealthy families. One startling statistic: only half of the public-school students in California are at grade reading levels; the numbers for math are even worse. As she writes, "Shouldn't the schools that serve poor children be the very best schools we have?"
Extrapolating from that idea, we can ask the same of all parents: shouldn't we work toward supporting children in the very best manner possible? Be it through influence or attention, it seems that too much of anything is usually counterproductive. Kids need to learn on their own terms, too.
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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."
