With an Introduction by Jeff Wallace. 'A grain in the balance will determine which individual shall live and which shall die.'. Darwin's theory of natural selection issued a profound challenge to orthodox thought and belief: no being or species has been specifically created; all are locked into a pitiless struggle for existence, with extinction looming for those not fitted for the task. Yet The Origin of Species (1859) is also a humane and inspirational vision of ecological interrelatedness, r