The overriding mystery, the review tells us, is that humans in all societies laugh (making a very similar noise in the process) but that what we all laugh at varies hugely between cultures and across history, thus making it extremely difficult to say what the function of laughter is.
Several theories have apparently been espoused, but none of them are entirely successful in explaining all that we find funny and when. There's the notion of laughter as an expression of superiority, in which the laugh is a form of mocking sneer. It's easy to see how racist and sexist jokes fall into this category. Incongruity theory claims we laugh at odd combinations, or the unexpected. There's Freud's relief theory - which, you guessed it. And finally there's the idea of laughter as a social survival mechanism for escaping awkward situations.
Of course, psychologists too have covered this territory - the work of Richard Wiseman and his search for the world's most popular joke comes to mind.
My favourite part of the review comes when Mary Beard, the reviewer, provides a (most probably) unique example of an instance from Roman Times "when we can follow in detail the story of a laugh, and share something of its physical experience."
"The laugher in question," Beard explains, "is Dio Cassius, historian and Roman senator. During the reign of the emperor Commodus (180–192 AD), the terrible son of Marcus Aurelius, Dio attended the games in the Colosseum, where (not wholly unlike the scenes recreated in the movie Gladiator) the emperor himself was performing. He had scored a number of victories against animals (comparatively safely, since the particularly fierce ones were presented to him in nets), and had just succeeded in decapitating an ostrich. Dio himself was sitting with the other senators in the front row and gives an eyewitness account of what happened next:The story captures an intriguing aspect of humour, which is that laughter can feel all the more irresistible when you know you shouldn't be doing it. And from that situation, whether in the headmaster's study or the chief executive's office, cheeky pupils or errant employees can find themselves descending from laughter into a disabling state of hilarity at just the moment when they really ought to be conveying an air of sombre reflection. I agree with Beard that there is something rather touching about a Roman senator experiencing such a recognisable sensation when sat before the emperor, revealing as it does how the universality of human experience stretches through the millennia.
'He came up to where we were sitting, carrying the head in his left hand and in his right hand holding up his bloody sword. He spoke not a word, yet he wagged his head with a grin, indicating that he would treat us in the same way. And many would indeed have perished by the sword on the spot, for laughing at him (for it was laughter rather than indignation that overcame us), if I had not chewed some laurel leaves, which I got from my garland, myself, and persuaded the others who were sitting near me to do the same, so that in the steady movement of our jaws we might conceal the fact that we were laughing.'"
Link to review of books about laughter in New York Review of Books.