Sorry, not Mark Twain. It was written in 1971 by M. J. Shields¹. It has since been frequently mis-attributed to Mark Twain, who only wrote about a similar topic in 1899².
Ah, another quote misattributed to Twain. Looks like it was submitted as a letter to The Economist in 1971 — I'll update the parent. Thanks for pointing this out!
1. http://www.lettersofnote.com/2012/05/iorz-feixfuli-m-j-yilz....
2. https://ebooks.adelaide.edu.au/t/twain/mark/what_is_man/chap...