And I doubt if many would agree to classify as “complex” life the blue-green algae which for more than three thousand million years have been forming stony stromatolites – and still are, in a pool in Shark Bay on what is now the north-west coast of Australia.
Of course complex life does not “pop into being” in a blinding flash.
The exploration of Mars has revealed that it might once have had conditions capable of supporting simple life – but probably not the “little green men” of science fiction.
They would have taken longer to evolve.
Life appears and thrives in places on Earth which until recently were thought uninhabitable.
Stanley Miller’s famous experiment in the early 1950s boiling up inorganic chemicals in a flask produced a “soup” of organic compounds, the “building blocks” of life, as Crick and Watson’s understanding of the DNA molecule later showed.
Being unable to explain exactly how life started here is hardly surprising, since no intelligent life existed on Earth over 3 billion years ago to record the event.