I'm reminded of that Shakespeare quote "I could be bounded in a nutshell, and count myself a king of infinite space...". We're so primitive as a culture and know so little about the universe that all we can really do is choose a belief that fits comfortably within our realm of knowledge, or accept the fact that we don't know and that any logical theory is as valid as another in the absence of evidence.
We don't know what amount of time is required for life to spontaneously form in a given set of conditions. If we found it to be one day, in ideal conditions then yes, it's very likely it spontaneously formed here, daily. If it required several billion years for it to spontaneously form and take hold then I would say it's more likely it evolved elsewhere and that the primary form of creation is transmition.
We don't know how much other life is out there. If our Milky Way galaxy was found to be primary sterile?
There are many questions, and that's why Neil deGrasse Tyson is arguing for a bigger space program. We'd like answers.