Problem with this ‘theory’ is that very few human cells have a long life outside an organized structure like the brain or the kidney.
free floating cells, perhaps ‘stem’ cells from the placenta (?) might make it across the barrier and into the mom, but, how they would persist is hard to explain.
Decades after birthing a child, the mother can still have cells from that baby residing in her uterine tissues. There may be stem cells in seminal fluid. There are certainly stem cells in the uterus.
Male cells can be found during autopsy in the brains of women who are 60, 70, or older.
The cells have everything they need to survive in the mother’s body. I think that the cells that cross the placenta are not programmed to develop further, but simply to integrate themselves into the host (mother) and survive.
I hypothesize that this may be one reason the immune system does not recognize the baby as a foreign invader and kill it—because the baby’s cells become part of the mother’s body, therefore causing them to be recognized as “self” by the immune system. A related function may be that the presence of the children’s cells strengthens the maternal instinct.
I can tell my sons that they will always be a part of me...
How die mitochondria first get into nuclei? Could this be a related mechanism?