Did life start on Earth? Take a bunch of organisms, plot the log(genome size) versus time of first fossil. You get a complexity doubling time of ~400 million years. Going all the way back to 'zero complexity' though lands you ~8 billion years before the Earth formed.

The tough part here is the earliest fossils of life were found pretty soon in Earth's history, just 900mya after it formed. Assume living systems start *right away* growing in complexity, it would be a doubling rate of 30 mya years to prokaryotes. Then flatlined to 400 mya

What's more likely, early life had an extremely fast complexity doubling rate that is 12x the rate we see across all of the actual fossil record, or... It just took 900 million years for some spores that 8 billion years in the making to rain down on Earth?

Btw this is a very unsophisticated argument