If aliens landed at a lecture they’d be very confused about what’s going on at the end. Why is it we strike our hands together violently to indicate we’re appreciative of what someone did? It’s an odd thing, an arbitrary cultural act that could have been just about anything. Slapping knees, howling, singing a song, all could have been the tradition just as easily as clapping.
In an article in Esquire, Elwyn Simons, head of Duke University’s Division of Fossil Primates, says “We don’t know know how far back it goes… but you don’t find primates doing it unless they’ve been taught to do it. They do not clap hands in the wild. It’s not to applaud something. It’s because they’re frightened or want to call attention to food”.
Jay Fisher, a professor at Yale University, dates the custom to the 3rd century BC, where (Greek?) plays ended with a request, plaudite, for the audience to clap. Wikipedia offers some tidbits from ancient Rome, likely one of the first places where clapping as a cultural phenomenon was recorded.
Various cultures throughout history have had alternatives to clapping. The Romans, and hipsters in the 60s, snapped their fingers. I know, first hand, that Bruce Springsteen fans yell “Bruuuuuce” at his concerts, which to the uninitiated, sounds exactly like people booing.
I also find it interesting, when I’m in the audience, to try and be the first person to clap. Often there’s silence when performances, or lectures, end, and whoever claps first can always start a good number of people clapping. It’s a strange phenomenon. Almost as strange as standing ovations.