If so, amoebas are more efficient. There's no reason whatsoever to assume that all life on Earth arose from a common ancestor, or that all life originated at the same time. There need not have been a single magic instant and location which was uniquely suited to the spontaneous generation of life. For ages, and at countless locations, conducive conditions probably existed, if they ever did. Here's another interesting idea.
Some animals live a long time.
Maybe even a hundred years. That's a long time in the evolutionary history of a microbe fresh off the theological drawing board. Thank you, Jonathan, for the conundrum. Perhaps they still do. Most likely, we'd exterminate it.