I got confused with the timey-wimey monster and thought the sacrifice had already happened (and was a bit disturbed that, even if Agatha was in the madness place, she hadn't objected). So, doubly glad to see Violetta's alive.

I wonder if Steelgarter doesn't differentiate between "dead" and "good-as." It's a common, semantic error with villains (hmm, the connection between villainy and certain verbal processing disorders, possibly connected in some way to the need to make elaborate death traps but never take the time to see if they work [which seems like an attention deficit related problem, but the co-existence of the two is too high to be ignored]).

On the re-occurrence of Sparks: According to what I read on the Mayo Clinic's site, 30% of hemophilia cases seem to be caused by a spontaneous mutation when there was no history in the family (Queen Victoria may be an example, but I'm not 100% sure).

It may be Sparkyness is similar. Although, we don't know how common the trait is outside of Europa, if stat numbers are about the same in other population groups, we could assume it appears spontaneously in populations or that it dates back to very early in human development and is more or less equally spread among all human populations. Of course, time travel may have also played a part in its distribution (oh, no, did I just suggest Barry is the ancestor of all Sparks? Wait, would that make all Sparks Heterodynes? Or do they still count after 20,000 years or so?). It's also possible some Sparks travel a lot more than other members of their population groups, again messing the stats.

So, boiling that down (and discarding time travel):

1. If Sparks are more present in Europa, we can assume a common, genetic ancestor and that Othar's goal might be doable.

2. If Sparks are equally present in most or all population groups, spontaneous mutation becomes more likely.

3. Although it's also possible that the trait appeared early. Its persistence (despite the high death tolls associated with it) suggests that it may have an evolutionary advantage (although that might be an advantage for people with the Spark surviving in a world full of Sparks rather than population groups surviving because of the Spark).

4. A limited geographical area with lots of Sparks might also mean an environmental factor that encourages the emergence of the Spark, like the way the Dyne influenced the Heterodynes (they are noted for the strength of their Spark and its high level of occurrence in the family).