By Patrick Appel
Mary Beard looks at the origins of laughter:
Theorists and scientists…have shown that laughter from tickling is not quite the reflex response we often assume it to be. For a start, it is next to impossible to raise a laugh by tickling yourself (whereas you can easily make your own leg jerk by striking your patella with a hammer). It is also the case that when tickling happens in threatening rather than friendly circumstances, it doesn’t produce laughter, but screams or tears. Hence the conclusion that—while there may be some purely biological prompts to laughter…the link between tickling and laughing is largely a social one, not a reflex at all. From this stems a range of theories that go on to explain laughter as the result of evolutionary adaptation within early society. One idea is that laughing functioned as a "false alarm" device. It was a sign to primitive hominids that despite all the rumpus that other hominids were creating, this was no enemy attack but friendly knockabout.