Attention future students in my Brit Lit II (and perhaps The Victorian Age) courses: When it’s time to sit the exam on the Victorian period, you can count on the following question appearing as extra credit:
Why can’t Tennyson’s famous line about “nature red in tooth and claw” refer to Darwin’s theory of natural selection?
The answer has nothing to do with any alleged peacefulness or gradualness about Darwin’s theory.
In Memoriam was published in 1850; On the Origin of Species, 1859. Darwin could (and did!) use the line to illustrate his theory–but, absent a time machine, Tennyson’s poem can’t refer to Darwin’s idea.