With it Wallace sent Darwin a memoir, asking him to present it to the Linnaean Society: on examining it, Darwin found that Wallace had independently arrived at conclusions similar to his own--possibly had deprived him of fame; but Darwin was loyal to his friend, and his friend remained ever loyal to him.

He publicly presented the paper from Wallace, with his own conclusions; and the date of this presentation--July 1, 1858--separates two epochs in the history, not merely of natural science, but of human thought.
In the following year, 1859, came the first instalment of his work in its fuller development--his book on The Origin of Species.

In this book one at least of the main secrets at the heart of the evolutionary process, which had baffled the long line of investigators and philosophers from the days of Aristotle, was more broadly revealed.

The effective mechanism of evolution was shown at work in three ascertained facts: in the struggle for existence among organized beings; in the survival of the fittest; and in heredity.

These facts were presented with such minute research, wide observation, patient collation, transparent honesty, and judicial fairness, that they at once commanded the world's attention.