"But how else did it start? Some people propose that life was seeded from other parts of the universe, but that poses the question, 'How did it start there?'."
Professor Steel said he believed that "the formation of life, given the conditions on earth, was not particularly unlikely" considering the chemical network at the time.
"But whether there are other life forms in the universe staring out into space and wondering if they are alone or not, that's a totally different question," he said.
Work by Professor Steel and other researchers on how life began on Earth will be presented at the Origins of Life meeting in Princeton, US, next week and at the European Organisation for Nuclear Research in Switzerland next month.
He said the origin of life was quite controversial among scientists with many theories but relatively little data.
"Our findings are helping to provide a mathematical explanation and they suggest that the spontaneous emergences of the first steps of life are more likely than had been supposed by many working in this field," Professor Steel said.
The work is a collaboration with former UC post-doctorate Dr Wim Hordijk from Switzerland, US-based theoretical biologist Stuart Kauffman and other scientists working on the origins of life and synthetic biology.