Our Selves, Other Cells - Boing Boing:
"How many people have left their DNA in us? Any baby we’ve ever conceived, even ones we’ve miscarried unknowingly. Sons leave their Y chromosome genes in their mothers. The fetal cells from each pregnancy, flowing in a mother’s bloodstream, can be passed on to her successive kids. If we have an older sibling, that older sibling’s cells may be in us. The baby in a large family may harbor the genes of many brothers and sisters. My mother’s cells are in my body, and so are my daughter’s cells, and half my daughter’s DNA comes from her dad. Some of those cells may be in my brain. This is squirm-worthy."