I'm studying Darwin for my most current PhD chapter, and found this story in the Editor's Introduction to Darwin's The Origin of the Species, written by Jim Endersby. He writes:
"On the morning of Thursday, 19 October 1871, 'a respectable-looking young man deliberately climbed onto the parapet of the bridge and jumped into the River Eden' at Carlisle. Despite the efforts of several witnesses to rescue him, he drowned. According to the following day's Morning Post, an old man appeared at the local police station a few hours later, carrying a parcel which the drowned man had given him five shillings to deliver. It contained a guinea to reward whoever found the body and brief diary, which revealed the dead man's name to be Samuel Howard and recorded his last thoughts.
"According to the Post, Howard 'gave as his reason for self-destruction that, the Darwin theory having proved men to be descended from monkeys, he did not desire to live any longer'. Punch picked up the story and, with characteristic sensitively, commented that 'No coroner's jury can, in this instance, have hesitated to find a verdict of insanity'–but suggested that Howard had died in vain, since the absence of mental disturbance and suicide among apes proves that we are not related to them" (lvi-lvii).