The story is told of the zookeeper who one day was passing the monkey house. He looked in and saw a monkey sitting on the branch of a tree with the Bible in one hand and Darwin's "On the Origin of Species" in the other.
"What are you doing?" asked the zookeeper.
The monkey replied, "I'm trying to discover whether I'm my brother's keeper or my keeper's brother!"
(not really a joke as such ... but thought-provoking, I hope)