The science of how women can have twins with 2 different fathers
For instance, mothers mount different immune responses to male and female fetuses; having both in the uterus at the same time could create an unusual set of circumstances for the female twin, irrespective of hormonal input. Something not acceptable 30 years ago could be more acceptable today.
It's possible that these effects have something to do with the adherence of female-bodied individuals to traditional gender norms. Based on the metrics recorded by the Norwegian government, the researchers determined that women with a biologically male, rather than female, twin were Additionally, at age 32, these women were By that age, they were also 3.
But often more striking than what twins have in common are the differences between them—or, perhaps, how they might change each other. Support Provided By Learn More. Though the root causes of these differences remain unclear, the discrepancies held true even for females whose twins died shortly after birth.
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If a woman shared the womb with a male, instead of female, sibling, she might be more likely to drop out of high school or college, earn less in adulthood, or be unmarried or have fewer children in her thirties. This, it seems, would implicate something in the uterus. To analyze birth, household composition, schooling, and employment data, the researchers examined records of 13, twins born between and in Norway, which, like all Nordic countrieskeeps detailed nationwide registries of its population.
Got a Penis? Both smaller-scale experiments yielded similar—but not identical—.
There was no effect on a final factor—whether or not women chose a STEM or economics major in college. Share this article.
Girls who share a womb with boys tend to make less money than those with twin sisters
Others are more skeptical. Image Credit: HannamariaH, iStock. Katherine J. Wu KatherineJWu. Address. All of this is just a teeny lens into the vastness of human diversity.
Presumably, this rules out the effects of growing up alongside a sibling of the same age—and hints at the possibility that these women might be experiencing long-term biological of sharing the womb with a brother. Our Sponsors Draper.
Twins often look or behave similarly, but they might be able to influence and change each other even before they're born. Many differences exist between the male and female fetal environment, raising the possibility of other explanations, says McCarthy, the University of Maryland neuroscientist. This might be especially true if the women came of age in a society with highly restrictive and unforgiving gender norms, McCarthy says.
These caveats are important to keep in mind given the near doubling in rates of twin births since —spurred on by an increase in the average age of conception in women, as well a rise in the use of fertility drugs and assisted reproductive technology. Zip Code.
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Receive s about upcoming NOVA programs and related content, as well as featured reporting about current events through a science lens. Still, even with these much smaller datasets, the overall trends remained, Kuzawa argues, suggesting that the drivers behind these phenomena were taking hold before birth. With thousands of records to sift through, however, the researchers were able to repeat their analyses on a subset of women whose male twins died within the first year of life and again for the of those whose twins died within the first month and had thus been raised without their brothers.