Who trusted God was love indeed
And love Creation's final law --
Tho' Nature, red in tooth and claw
With ravine, shrieked against his creed.
--Alfred, Lord Tennyson
Tennyson's quote comes from a group of cantos entitled, "In Memorium A.H.H." (1850). This quote comes from canto LVI. The Oxford Dictionary of Quotations, 3rd Ed.
Richard Dawkins used this quote in his book, "The Selfish Gene," to summarize the behavior of all living things which arises out of the survival of the fittest doctrine of evolutionary biology. His unsentimental view of behavioral biology was originally unpopular when the book was published in 1976, coming at a time when the prevailing worldview of human behavior was tabula rasa, that all men were created equally, with the same potentialities, who could be brought up in cultures which could bring up children who knew only love and not hate, and who could be taught that competition for mates, material acquisitions, or sports trophies were a thing of the past.
Dawkins used the quote as a corrective, reminding us that we humans are born into a world with pre-existent genetic imperatives that cause us to be competitive despite the best efforts of education and religion to suppress those imperatives.
"How long he stood he did not know, but there was a foolish and yet delicious sense of knowing himself as an animal come from the forest, drawn by the fire. He was a thing of brush and liquid eye, of fur and muzzle and hoof, he was a thing of horn and blood that would smell like autumn if you bled it out on the ground. He stood a long long time, listening to the warm crackel of the flames." - Ray Bradbury, Fahrenheit 451
Thanks to unperson for pointing out the passage.