We have only one sample of a planet with life. To draw universe-wide conclusions from that one sample is ridiculous! We have discovered other planets with more-or-less Earth-like conditions. But they are so far away that we can barely conceive of a technology that could carry a ship full of humans to one of them. Even if that generation starship is built, by sheer bad luck it could be destroyed by a collision with "space junk," or by failure of degradation of its own technological infrastructure, or by the crew inventing a new religion run by a god who thinks that humans are parasites in his universe and therefore demands that they commit mass suicide. If the ship manages to surmount these possibilities, the nearest quasi-Earth is so far away that radio communication will fade away within a few years. By the time the great-great-great-etc. grandchildren of the original crew arrive, life on our planet may be considerably different from today--if we manage not to annihilate ourselves in a nuclear war. By the time that THOSE people's great-great-great-etc. grandchildren resupply the ship (or perhaps build a better one with the technology of their new hosts) and make the return trip, they may be nothing but legends to the people they find here--who may have bombed themselves back into the Stone Age. Because you're working with a SAMPLE OF ONE. Surely you understand that this is not proper science! There may be zillions (pardon my technical jargon) of planets scattered throughout the universe. Until we find a few upon which life arose, we have absolutely no way to answer your question. Our own ancestors made the progression from making tools out of stone but not knowing how to create fire... to industrial technology, computers and controlled nuclear energy... in less than 15,000 years. That is truly a blip on the cosmic calendar. There's no good reason to be thinking about "tens of millions of years." Even if our biosphere was the very first one in the entire universe where life arose, we have no reason to assume that it's not going to arise somewhere else next Tuesday.