If life arose gradually from chemicals here on earth, it had plenty of time and plenty of space to do it. It only had to do it once. There were no predators. Forms of life that would have no chance today could survive back then without competition. It seems to be also quite possible now we have discovered that earth like planets are common, that life abound in our galaxy. Life was seeded here on earth. For some reason, many lifeforms on earth are so tough they can survive hitching rides on comets. Why would they have such abilities if they never used them?

In that case life has had hugely more time and hugely more places to get started. It could require the freakiest event imaginable and still have happened many times.

Science has not solved this yet, but they have made progress.

Can Science Explain the Origin of Life? click to watch
~ Roedy (1948-02-04 age:70)