In his book, Darwin never mentioned the origin of life. The primitive understanding of science in his time rested on the assumption that living things had very simple structures. Since mediaeval times, spontaneous generation, the theory that non-living matter could come together to form living organisms, had been widely accepted. It was believed that insects came into existence from leftover bits of food. It was further imagined that mice came into being from wheat. Interesting experiments were conducted to prove this theory. Some wheat was placed on a dirty piece of cloth, and it was believed that mice would emerge in due course.

Louis Pasteur destroyed the belief that life could be created from inanimate substances.

Similarly, the fact that maggots appeared in meat was believed to be evidence for spontaneous generation. However, it was only realized some time later that maggots did not appear in meat spontaneously, but were carried by flies in the form of larvae, invisible to the naked eye.

Even in the period when Darwin's Origin of Species was written, the belief that bacteria could come into existence from inanimate matter was widespread.

However, five years after the publication of Darwin's book, Louis Pasteur announced his results after long studies and experiments, which disproved spontaneous generation, a cornerstone of Darwin's theory. In his triumphal lecture at the Sorbonne in 1864, Pasteur said, "Never will the doctrine of spontaneous generation recover from the mortal blow struck by this simple experiment."2

Advocates of the theory of evolution refused to accept Pasteur's findings for a long time. However, as scientific progress revealed the complex structure of the cell, the idea that life could come into being coincidentally faced an even greater impasse. We shall consider this subject in some detail in this book.