This is a great example of people purposely taking research results out of context and using it to promote an agenda. The subliminal message? Don't have (casual) sex, you don't know what DNA you are absorbing! And even insinuate it may be relayed to neurological diseases. Reality: they cite 2 different papers and combine the results to make it look scary. Paper 1, the one that found 63% micro chimerism. They did not quantified how many of their subjects have had a son. Only one person was described as never having a live child. Did not report on spontaneous or induced abortions. So if all but one the women had have children, it is expected that at least 50% may have boys. Add that to the percentage of women that may had aborted (spontaneous or not) a male fetus, 63% does not require other explanation more than pregnancy. And the study found that women with microchimerism had LOWER levels of Alzheimer's than the ones without. Second study (different set than the first): they separated the subjects according to whether they had female kids, abortions or no reported pregnancy (keep in mind that the rate of spontaneous abortion among all fertilization events is about 30-50%, most without the woman ever realizing she was pregnant). The over all rate of microchimerism on this group of women without male children was 23% , not 63% as in the previous study. And the level for women never pregnant or only daughters was 10 and 9% respectively. The only group that had a level comparable to the previous study was the women that had had an abortion, and since we would expect that 50% of the fetuses would have been male, that is not surprising. So what about the 10% in the never pregnant woman? Again, while it is impossible to say for sure, it could be explained if they had miscarriages that never knew about. None of this supports the sensational title of this article