Even those far removed from Jewish learning know that it is the mother who determines the Jewish status of a baby. Why this is so is not clearly spelled out. The simplest and most obvious reason would seem to be the fact that while we always know who the mother is, the identity of the father is less certain. The Talmudic assertion that "the majority of relations a woman has is with her husband" (Sotah 27a) is just that--a claim about the majority. However, a minority are not.