Recently, two University of Pennsylvania researchers announced findings that, in the words of the Washington Post, "could blur the biological line between fathers and mothers." Writing in the online journal Science, Hans Schoeler and Karin Huebner described how they turned ordinary mouse embryonic stem cells into eggs capable of being fertilized. What’s more, the stem cells they used were from males. Thus, if the technique used by the two researchers is applicable to humans, it could be possible for a gay couple to have children "with one man contributing sperm and the other fresh eggs bearing his own genes." That...