So I've been spending the day reading some Darwin, and chapter eight of On the Origin of Species (first ed.), with the captivating title of "Instinct", caught my attention this time. Darwin has two great realizations in this chapter; first he lays out how behaviors can evolve just as physical structures can; how shared ancestry and descent with modification can explain how related species on different continents can exhibit the same or similar behaviors. The second insight lies in his explanation of the, to us, very cruel behaviors that you often find in nature. To people of Darwin's time, it would be a problem to consider that a benevolent creator would have put on the earth creatures that not only killed in order to survive, but that did it in almost unnecessarily horrific and macabre ways.
How does Darwin solve the question of the, in our eyes, unnecessary cruelty in nature? By explaining it in terms of natural selection and abandoning design and benevolence. The conclusion of chapter eight reads:
Finally, it may not be a logical deduction, but to my imagination it is far more satisfactory to look at such instincts as the young cuckoo ejecting its foster-brothers, - ants making slaves, - the larvae of ichneumonidae [parasitic wasps, see below] feeding within the live bodies of caterpillars, - not as specially endowed or created instincts, but as small consequences of one general law, leading to the advancement of all organic beings, namely, multiply, vary, let the strongest live and the weakest die.
Ichneumonid wasp. Most of the parasitic wasps of this order survive by laying their eggs within the bodies of caterpillars. The larvae feed on the living caterpillar from the inside, consuming the most life-supporting tissues last in order to ensure the longest viability of their prey, and prolonging its perceived misery. Ref: Flickr
In one of many letters to his friend, the American botanist Asa Gray, it becomes just how clear and deep this insight is:
With respect to the theological view of the question; this is always painful to me.— I am bewildered.— I had no intention to write atheistically. But I own that I cannot see, as plainly as others do, & as I shd wish to do, evidence of design & beneficence on all sides of us. There seems to me too much misery in the world. I cannot persuade myself that a beneficent & omnipotent God would have designedly created the Ichneumonidae with the express intention of their feeding within the living bodies of caterpillars, or that a cat should play with mice. Not believing this, I see no necessity in the belief that the eye was expressly designed.
Preferring to see nature as governed by laws, Darwin realizes that the laws that govern the formation of an organ such as the eye must be the same that govern the formation of instincts and behaviors, whether they be perceived as benevolent or cruel. If a design argument cannot explain the unnecessary and cruel infliction of suffering on the part of some animals, it's not likely to explain anything else in nature. Perhaps to avoid offending his good friend and supporter, who was a devout Christian and believer in design, Darwin concludes:
On the other hand I cannot anyhow be contented to view this wonderful universe & especially the nature of man, & to conclude that everything is the result of brute force. I am inclined to look at everything as resulting from designed laws, with the details, whether good or bad, left to the working out of what we may call chance. Not that this notion at all satisfies me. I feel most deeply that the whole subject is too profound for the human intellect. A dog might as well speculate on the mind of Newton.— Let each man hope & believe what he can.—
The discussion about how Darwin saw cruelty in relation to evolution and natural selection is very relevant within the context of how it applies to human societies. At best, Darwin is conflicted about the idea of "survival of the fittest", or as he put in at the very end of chapter eight - "multiply, vary, let the strongest live and the weakest die." Many attempts have been made by those that deny and criticize evolutionary theory to characterize Darwin's theories as justification for such horrible acs of cruelty as genocide and the killing of "weaker elements" in society. However, if you read chapter eight of "Origin" or Darwin's notes and correspondence on the subject, it's obvious that just as cruelty and suffering are "small consequences of a general law", so are kindness and empathy.
In chapter five of The Voyage of the Beagle Darwin describes how the Spaniards treated the indigenous population of South America:
This is a dark picture; but how much more shocking is the unquestionable fact, that all the women who appear above twenty years old are massacred in cold blood! When I exclaimed that this appeared rather inhuman. he answered, "Why, what can be done? they breed so!" Every one here is fully convinced that this is the most just war, because it is against barbarians. Who would believe in this age that such atrocities could be committed in a Christian civilized country?