ABSTRACT
About 4.5 billion years ago a supernova exploded. Its wreckage was propelled into a nearby cloud of hydrogen gas and interstellar dust where, compressed by its own gravity, it formed the sun at its centre. Around this sun, a disc of leftover debris swirled. The timescales over which life has evolved are truly mind-boggling. To get some relative sense of the time periods involved, it can be helpful to shrink the whole story down to just 24 hours. The mystery of life's origins shows no sign of being solved soon and the debates will rage on. Happily, however life started, there is at least some general agreement that the most ancient fossilized ancestor was a prokaryote. Prokaryotes, like all organisms, face the challenge that their world can change. Even if all else remains the same, just an organism's habit of harvesting local resources will change its environment.
