Well, I think if I assume that all the relevant bodies (humans and trains) are on the Earth then I'm fine.  But pushing it a bit further, as long as all the humans and trains we are talking about are decended from humans and trains from the Earth then I think I'm still fine because any human not on the Earth who is decended from a human on the Earth can be traced back to a human on the Earth via a finite amount of time and distance.  The distance may be great, but it would still be finite.

Perhaps a little more on topic, I don't think they're actually postponing the sig campaign when people bump this thread.  I understood the threat to be aimed at people asking "daddy are we there yet?" about when it starts.