Instant Genius How our bodies are host to mysterious cells that came from other people
Oct 19, 2025
In this enlightening discussion, science writer Lise Barnéoud, author of Hidden Guests, delves into the fascinating world of microchimerism. She reveals how our bodies host cells from our mothers and even from past siblings, challenging the notion of a singular identity. Lise shares intriguing cases, like a woman giving birth to her twin sister's genetic children, and discusses the potential health implications of these foreign cells. Explore how microchimerism could redefine family connections and our understanding of self.
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Human Bodies Contain Other People’s Cells
- Some of the human cells in our bodies come from other people and are called microchimeric cells.
- They are rare (about 1 per 10,000–100,000 cells) but carry a different genetic signature.
Viral DNA Helped Humans Implant Embryos
- Trophoblast cells invade the uterine lining using a viral-derived gene to fuse and penetrate maternal tissue.
- This ancient viral contribution (e.g., the HERV gene) enabled placental implantation and may have enabled live birth evolutionarily.
Fetal Cells Can Engraft In Mothers Long-Term
- Fetal cells cross the placenta into the mother and can engraft in maternal organs for life.
- These cells act like stem cells, self-renewing and forming small persistent cell populations.
