It was part of the book, Arrival of the Fittest. The author somehow quantified the scale of the space of all possible chemical reactions and it was just so huge

It was part of the book, Arrival of the Fittest. The author somehow quantified the scale of the space of all possible chemical reactions and it was just so huge that the chance of the citric acid cycle emerging was just infinitesimal, like 1 in 10^100 or something. Like winning the lottery 10 times in a row type of thing. Found it an intriguing idea. Would be curious to see the counter argument, though it's likely to be beyond me mathematically.