An old joke definition of a cannibal is:
 
Q: What is a cannibal?
A: Someone who is fed up with people.
 
The joke has been cited in print since at least July 1943, when the newspaper PM (New York, NY) reported it from the radio station WEAF.
 
“Why did the cannibal live on his own?”/“He was fed up with other people” is a similar joke.
   
 
Old Fulton NY Post Cards
7 July 1943, PM (New York, NY), “Heard and Overheard” by Jerry Franken, pg. 26, col. 5:
“A disgusted cannibal is one who’s fed up with people.”
(Heard on WEAF radio.—ed.)
   
Google News Archive
20 November 1943, Berkeley (CA) Daily Gazette, “A Letter Especially For Your Boy Now in the U. S. Armed Forces” by Hal Johnson, pg. 7, col. 1:
Looking around for the weak story of the weak, take this one from the Berkeley Lion’s Club’s Jungle Weekly: “Said one cannibal to the other cannibal over the jungle party line after dinner, ‘I get so fed up with people some times.’”
 
Google News Archive
9 April 1948, Milwaukee (WI) Journal, GreenSheet, pg. 2 headline:
An Old Pessimist Says, ‘I Feel Just Like a Fat Cannibal—All Fed Up With People’
 
30 July 1948, Rhinelander (WI) Daily News, pg. 8, col. 6:
As one cannibal said to the other after lunch, “I get so fed up with people sometimes.”
(Stumpf’s Service Station.—ed.)
 
4 March 1951, Arkansas Democrat (Little Rock, AR), “Jackpot Jokes” compiled by Jack Shafer, Magazine, pg. 14, col. 4:
“As one cannibal said to another, ‘I get so fed up with people no and then’.”—Jimmy Durante.
 
Google News Archive
6 April 1951, Milwaukee (WI) Journal, GreenSheet, pg. 1 headline:
A Bus Driver We Know Says He Feels Like a Cannibal Chief, All Fed Up With People
 
Google Books
The Speechmaker’s Complete Handbook:
A storehouse of colorful, point-making material and complete planning guide for public speakers
By Edward L. Friedman
New York, NY: Harper
1955
Pg. 241:
A humorist has added another classification which he says is the most pathetic case of all. That is the case of the poor cannibal who is fed up with people.
 
Google News Archive
13 October 1976, Spartanburg (SC) Herald, “The Stroller” by Seymour Rosenberg, pg. 1, col. 1:
And did you hear about the vegetarian cannibal who was fed up with people?
 
Google Books
20,000 Quips & Quotes
By Evan Esar
New York, NY: Barnes & Noble Books
1995, ©1968
Pg. 110:
There was once a cannibal who complained he was getting fed up with people.
 
Twitter
Talking Moose
‏@TalkingMoose
Cannibal: One who gets fed up with people.
2:00 PM - 2 Feb 2009
 
Twitter
Talking Moose
‏@TalkingMoose
Cannibal: Someone who is fed up with people.
12:00 PM - 16 Feb 2009
 
Google Books
The Mammoth Book of One-Liners
By Geoff Tibballs
London: Constable & Robinson, Ltd
2012
Pg. ?:
Definition of a cannibal: someone who is fed up with people.
 
reddit
What is a Cannibal?
submitted July 25, 2016 by interrupt_
Someone who is fed up with people.