by Demand:
Women absorb and retain DNA from every man they have had sex with.
Rating:
In late February 2024, a claim that women were “storing DNA from every man” they had ever had intercourse with appeared on X (formerly Twitter):
Nothing in the above post is a biological fact.
The claim, which has been circulating online for years, stems from research into a phenomenon in which human female tissues contain male cells — male microsimarism. Most, but not all, cases of this condition result from tissue derived from a pregnancy with a male fetus. Although the source of male DNA in women who have never been pregnant is an ongoing question in science, intercourse is only one speculated source of male microchimerism.
The same claim has gone viral several times since 2012, usually in defense of conservative social politics. Snopes first checked the claim in June 2017, when a website called Your News Wire (which now goes by many including the People’s Voice) posted an article asserting that “Women are absorbing and keeping DNA from every man they have sex with.”
That article made the claim that a “new study” showed that cells transferred from a man to a woman during intercourse are integrated into that woman’s body after sex—”every single time.” In fact the study they referenced, published in PLoS ONE in 2012, showed male microdimerism in female brain tissue in 63% of the 59 women the researchers analyzed postmortem.
These researchers did not seek, nor did their study, draw any conclusions about the likelihood of male microsimarism occurring due to intercourse. The significance of the paper was that it showed that male cells were able to cross what is known as the blood-brain barrier – a semi-permeable membrane that prevents most chemicals in the blood from entering the brain. In fact, that study does not once mention intercourse as a suggested mechanism. This is as close as the 2012 study got to the source of those cells:
The source is probably male [microchimerism, Mc] the female brain consists of receiving Mc fetuses from a pregnancy with a male fetus. In women without sons, male DNA can also be obtained from an abortion or miscarriage. Pregnancy history is not known for all subjects but for some subjects in the present studies, thus male Mc in the female brain [tissue] it could not be judged by a specific previous pregnancy history. In addition to a previous pregnancy, a male female may acquire Mc from a known or missing male twin, an older sibling, or through a non-irradiated blood transfusion.
A paper published in 2015 investigated this matter further, concluding that — all possible mechanisms could contribute. From that paper, which was quite limited in its data set, it is clear that the transsexuality of male chimerism remains entirely speculative:
Data suggest that male microsimarism in young girls may come from an older sibling, either full or from an aborted pregnancy or a blood transfusion during pregnancy. We speculate that intercourse may be important but it is likely that there are other sources of male cells in adolescent girls.
Research since the original Snopes fact-check in 2017 has shed some additional, but not much, light on the origins and significance of male microchimerism. For example, in a study from September 2021, it was confirmed that male microchimerism exists in women who have never been pregnant. Although the authors acknowledged the hypothesis that intercourse could be a source, they said their study could not address that question and suggested other hypotheses:
Our study suggests that the origin of microsomal cells may not necessarily be a close family member. One source is sequential fetal-maternal exchanges over generations. Other possible sources are unreported or unrecognized interrupted pregnancy, breastfeeding, placental structure, pregnancy complications including preeclampsia and it has also been suggested that intercourse may play a role. We did not have these data available for a sufficient number of participants to perform a comprehensive analysis of these alternatives.
Taken together, all science can say with confidence that many — but not all — women have some male cells in their tissues and that most — but not all — cases involve a pregnancy with a male fetus. Science cannot answer with certainty whether intercourse is one possible source of male cells in cases where no pregnancy has occurred, but it cannot be absolutely said that a woman will store “DNA from every man who has penetrated her private parts without protection. ” Science is not even sure that such a phenomenon occurs at all.
Because the science underlying the claim that women retain the DNA of all the men they’ve slept with is misrepresented, the claim is False.
Sources:
Chan, William FN, et al. “Male Microchimerism in the Female Human Brain.” PLoS ONE, edited by Martin Gerbert Frasch, vol. 7, no. 9, September 2012, p. e45592. DOI.org (Crossref), https://doi.org/10.1371/journal.pone.0045592.
Funke, Daniel. “Fact Checkers have taken down this Fake News Site 80 times. It’s still being published on Facebook.” Poynter, 20 July 2018, https://www.poynter.org/fact-checking/2018/fact-checkers-have-debunked-this-fake-news-site-80-times-its-still-publishing-on- Facebook/.
Johnson, BN, et al. “Male Microchimerism in Females: A Quantitative Pedigree Duplication Study to Investigate Mechanisms.” Human Reproduction, vol. 36, no. 9, August 2021, pp. 2529–37. DOI.org (Crossref), https://doi.org/10.1093/humrep/deab170.
Müller, Amanda Cecilie, et al. “Microchimerism of Male Origin in a Cohort of Danish Girls.” Chimerism, vol. 6, no. 4, October 2015, pp. 65–71. DOI.org (Crossref), https://doi.org/10.1080/19381956.2016.1218583.
Yan, Zhen, et al. “Male Microchimerism in Women Without Sons: Quantitative Assessment and Correlation with Pregnancy History.” The American Journal of Medicine, vol. 118, no. 8, August 2005, pp. 899–906. DOI.org (Crossref), https://doi.org/10.1016/j.amjmed.2005.03.037.
