The following is extracted from an exchange on the newsgroup rec.arts.sf.written in early 2000, which started off about the dumb questions people ask writers (or computer programmers, or graduate students, or...), and drifted on to solutions to the problem.
Heather Rose Jones >
I've developed a theory that [everyone] should compose what I call the "cocktail party answer" to [the "what do you do" question?]. It needs to be complex enough to sound like a genuine answer, obscure enough to discourage further questions from someone who's just making conversation, and concrete enough to provide a "handle" for further interaction if the person is genuinely interested. My current version is "I'm working on a cognitive analysis of the grammaticalization of Medieval Welsh prepositions used for role-marking in verbal constructions". It seems to do the trick.
I had a similar line, as a response to questions like "And what is your next book about?" It ran, "Hydrological collapse of an agrarian civilization." Worked great.
Steve Taylor >
Except that for me (and half of the people posting here), it would make my eyes light up, and I'd start babbling incoherently about the how the Babylonians trashed their region by overirrigating and raising the salt table, and how I read a not-sufficiently-informative article in New Scientist about low tech Egyptian methods of reclaiming salinated land with brackish water, and then I'd drift sideways to the American Indian group in the southwest who pretty much blew away their culture by overlogging all the local timber, which would probably lead me onto a digression on The First Eden, a very nice ecological history of the Mediterranean, which has some good stuff about how the Romans overlogged the region to provide fuel and timber for ships, and then my brain would probably split into two so one half could talk about the modern presumption that low tech cultures are in balance with nature and make sustainable use of resources, while the other half would stick with The First Eden and talk about the Mediterranean emptying and refilling and landbridges and how Crete and Rhodes and Malta used to have pygmy hippos and mammoths, and how badly I want a pygmy mammoth as a pet of my own and how I promise I'd wash it and feed it every day, honest I would. Meanwhile the first half of my brain would have refissioned so that half of it could start talking about the (presumed) extinction by hunting of most of the big New World animals, and how Jared Diamond uses this in Guns Germs and Steel as a possible explanation for the lack of domesticatable animals in the New World, and then I'd start to hyperventilate and fall over from sheer excitement.
At no point, however, would I mention late Heinlein or gun control.