How many men in You ? Sperm & MICROCHIMERISM: Why Virginity Is Important or not ?
The basic idea here — that you can have another person’s DNA inside your body — is not BS. It’s known as chimerism, and it can happen in a few different situations — like in people who get bone marrow transplants. The term comes from “chimera,” a mythological fire-breathing creature with traits of a lion, goat, and dragon.
In that 2012 study, Nelson and fellow researchers were looking for what’s called male microchimerism — when women harbor small amounts of male DNA. They tested tissue from the brains of 59 deceased older women, searching for Y chromosomes, which are only present in males. They found that roughly 60% of the brains contained male DNA.
How did it get there? The most likely explanation is pregnancy.
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In the 1990s, scientists first discovered that, during pregnancy, a woman and a fetus can trade a small number of cells. In some cases, these swapped cells can be detected decades later in both mothers and offspring, Nelson, who’s recognized as a microchimerism expert, explained.
“The most common source of male DNA in an adult woman is from prior pregnancy with a male child,” she told INSIDER.
There’s no science to say that this DNA comes from sexual partners.
There’s no reason to think you’ll absorb DNA from your sex partners. Erik Lucatero/Unsplash
That viral news story also noted that women who don’t have sons can have male DNA in their bodies. That’s true, too. In 2005, Nelson and another team of researchers tested the blood of 120 women without sons. They found male microchimerism in 21% of them.
But there’s no actual science to prove that this DNA comes from having sex.
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“Any suggestion that male DNA is routinely retained from sexual partners has no support from any scientific study,” Nelson said.
Some studies have mentioned the possibility in passing, but at this point, it’s pure speculation that’s never been put to the test, she added. That’s a far cry from some outlets confidently claiming that women absorb DNA from “every man they have sex with,” as one headline read.
Besides, the idea that sperm can burrow inside you and hang out for decades doesn’t jibe with the fact that sperm dies after about five days inside the reproductive tract.
And if sex was really a cause of male microchimerism, Nelson and her team would have probably detected male DNA in more of the women they tested in 2005.
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“To me the biggest statement is the data,” she said. “If this were routinely happening, I mean, you would see it in the vast majority of adult women [without sons] that we studied.”
Most importantly, there are a handful of more plausible and actually-studied reasons that women without sons can harbor male cells.
Male DNA might come from a twin brother, an older brother, or a pregnancy that ended early.
fraternal twins newborn
You could get male DNA if you have a twin brother. Anna Azimi/Shutterstock
Nelson said that male DNA can occur in women who had a pregnancy loss or an unrecognized pregnancy. (Previous research shows that some miscarriages happen very early, before women even realize they’re pregnant.) And some women pick up male DNA while they’re sharing their mother’s womb with a male twin.
“Another possibility is to acquire it from an older male sibling,” Nelson said, though she added that this particular pathway hasn’t been formally shown in studies yet. “Your mom continues to harbor cells from the pregnancy with your older brother at a very low level, and so occasionally you might be able to acquire a cell from an older brother via your mother. I think most of us [in the field] believe that probably occurs, but not very commonly.”
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These days, Nelson’s lab is investigating ways this DNA mixing could actually benefit health. One exciting theory is that fetal cells might help mothers’ bodies detect and destroy cancer more quickly.
But for now, the bottom line is clear: That viral scare story about retaining sexual partners’ DNA makes sweeping claims that just aren’t supported by research.