Scientists have created artificial sperm from stem cells. Similar techniques can probably be used to create artificial eggs. Hence:

..it may even prove possible to produce sperm from female stem cells, and eggs from male ones, allowing homosexual couples to have children that bear the genes of both parents.

This would also enable a single man or woman to provide both the sperm and eggs needed to create an embryo, so that a person could essentially mate with himself or herself.

This means the arguments based on “marriage is about raising children” currently used against homosexual marriage may soon fall by the wayside. I always found those arguments weak anyway. Do supporters of that argument think that a woman past child bearing age should not be allowed to marry either? Or what of a man that is sterile? My view is that if two (or more) people want to get married to each other and spend their lives together then what’s the problem? Where’s the victim?