You might have your mom’s eyes, your uncle’s height, your older brother’s taste in music. But you might not know that sharing between family goes all the way down to the cellular level: you probably have cells from your mother, your older siblings, and most likely more of your relatives, living in your body right now. And if you’re a mother, you have some of your children’s cells too.
In early 2024, Atlantic staff writer Katherine J. Wu reported on an evolutionary adaptation that’s become one of modern medicine’s most confounding mysteries: what are your family’s cells doing in your body?
Wu explains how scientists believe these cells get there, how they affect your body, and how learning more about them could revolutionize medicine—from aiding in organ transplants, helping mothers with high-risk pregnancies, and more. “The simple fact that they’re allowed to stick around for decades, while they grow and develop and change,” Wu writes, “could have a lot to teach us about immunity—and our understanding of ourselves.”
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