“We are composed not only of human cells and microbes but also fragments of others…”
Lois Fordham/Millennium Images
Hidden Guests
Lise Barnéoud, translated by Bronwyn Haslam, Greystone Books
Having children conceived using donated eggs, one might assume that there is no genetic connection between the parent and the child. However, recent scientific discoveries have challenged this assumption.
Research has revealed that during pregnancy, fetal cells can cross the placenta into the mother’s body, integrating themselves into various organs. Similarly, maternal cells, and even cells passed from the grandmother to the mother, could also be present in the children. This concept of being a holobiont, consisting of not just human cells and microbes but also fragments of others, forms the basis of Hidden Guests: Migrating cells and how the new science of microchimerism is redefining human identity by Lise Barnéoud.
Barnéoud delves into the accidental discovery of microchimeric cells and explores how their interpretation has been influenced by societal and political factors. The idea that cells from family members can reside within our bodies evokes a range of emotions and reactions in different individuals.
While some find comfort in the connection to lost loved ones, others view it as a means for control or manipulation. Barnéoud navigates through these complexities, focusing on the scientific evidence behind microchimerism. She discusses how these cells can both benefit and pose risks to the individual, playing roles in tissue repair, tumor suppression, and autoimmune disorders.
Through engaging storytelling, Barnéoud shares fascinating cases where microchimeric cells challenge traditional genetic inheritance patterns. These include instances where a mother shares genetics with only some of her children or where cells from past partners are found in a person’s body years later.
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The presence of microchimeric cells can produce extraordinary biological mysteries
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Hidden Guests offers a clear and insightful exploration of this emerging field, using metaphors and analogies to simplify complex concepts. Barnéoud’s comparison of microchimeric cells to stars from distant galaxies adds a poetic touch to the scientific discussion.
The book also raises intriguing possibilities, such as the potential migration of cells from a partner’s seminal fluid to various parts of the recipient’s body. Barnéoud skillfully unpacks the implications of microchimerism on medicine and human identity, emphasizing the interconnected nature of genetic material.
As a parent who initially believed in no genetic link with her children, the revelations in Hidden Guests were both enlightening and reassuring. Barnéoud’s exploration of how we carry traces of others prompts contemplation on the complexity of human biology and relationships.
Helen Thomson is a writer based in London and a New Scientist columnist
