I remember the days when it was said that the mother is always certain, the father not. Even in those days, though, the fact that for any offspring there are exactly one mother and one father was never disputed.
In the last decade researchers trying to tackle a number of insidious diseases pinpointed them to a faulty mitochondria. Mitochondria are part of the oocyte and as such are always inherited by the mother (likewise, the Y chromosome is always inherited by the father).
In 2012 researchers found a way to get rid of the faulty mitochondria in an oocyte by extracting the DNA from the oocyte, inserting it in a oocyte taken from a different woman with no genetic alteration and fertilise it with the sperm coming from the male. The oocyte could then be inserted into the first woman womb to generate an offspring, a baby, that would have the genetic material coming from two mothers and one dad. The phenotype, the physical appearance, was the one of the natural mother and father but the chemical engine in his cells would run on a different mother mitochondria.
This method that could potentially avert several genetic diseases was never put into practice because of unexplored ethical issues. Now the FDA is to hold an hearing for the approval of clinical trials of this procedure that would indeed result in a baby having 2 mothers and one father.
The method has been experimented on monkeys and although it has produced healthy offsprings it may be too early to be sure that it does not have any side effect on the whole life cycle (what will happen to the offsprings of these offsprings...).
Clearly science is making possible new trails but we have no idea what might be around the first bend or the subsequent ones.
This is evident in genetics but similar issues are popping up everywhere as science, and technology, extended the human capabilities and life span.
What will happen once we will be able to read the minds of our fellows, may be by looking at them using a sort of Google glasses? One thing is to have a hearty laugh looking at Superman in the movie and his x-ray vision, another thing would be to have it. And, as the old Chinese saying warns: be careful on what you wish, you may get it!