Mitochondria and the origin of eukaryotes
If we assume single celled life is common, and exists in either all star systems, or in all systems without a hot Jupiter close to the star; then given the length of time involved here before eukaryotes, can we estimate how many planets in the galaxy have eukaryotes? 
Or how long it will be before some do?
Presumably increasing the length of time increases the probability of occurrence as would increasing the number of stars involved. Though how can we know if the event was statistically likely after that amount of time or whether we are deviations from the centre of the distribution (other than observing the quiet galaxy).
Surely we can have a rough idea now of where we stand