Sons' DNA remains in mothers' brains

This is just a PCR study. No evidence that the foreign human DNA even entered host cells, much less that it was expressed. Probably shows only that minute quantities of foreign human DNA can hang around a host body for a while. Most likely explanation is that it gets bound up in the extracellular matrix. Being that the DNA is of human origin, it would not trigger an immune response, but rather, it would just be slowly degraded like the host's own DNA when it is released from dead cells (part of the normal, perpetual turnover of cells). DNA is hardy stuff; people have sequenced DNA from Neanderthal bones.

Study co-author J. Lee Nelson's comments are ridiculous hype. He should be ashamed of himself. That those comments were published in this newspaper uncritically is also an embarrassment.

This work was published in PLoS ONE. PLoS ONE articles are peer reviewed only for the validity of the methods used, not for the importance of the subject matter or the validity of the conclusions drawn. This is where you can publish all sorts of meaningless crap.