In this thought experiment it is some time in the future, after we have learned how to design living bacteria from scratch. We then travel to a distant planet where we discover living bacteria, but nothing else. Do we assume that the origin of this bacteria did not involve direct intelligent intervention? Or do we assume that somebody designed it and placed it on this planet?
I’m editing this to include in the thought experiment that pre-biotic conditions on the planet would be the same as thought to exist on Earth before the first living bacteria appeared on it.