Well, it was partly alcohol. Don't kid yourself. Without this disinhibiting factor you would probably, as you do at work the rest of the year, have managed to keep your amygdala under control. The amygdala, otherwise known as the "lizard brain", is the most basic part of your brain, the bit your ancestors had even before they crawled from the primal swamp. It governs your powerful emotions (fear, anger, sexual desire and so forth) and instincts. A good deal of the rest of your brain is dedicated to ameliorating the more extreme effects of the amygdala. And if you dull those parts of the brain with booze and let your amygdala roam loose; all hell has a good chance of breaking loose with it.

The thing is, the reason people tend to behave so badly at office parties is that the office situation - however efficient it is at helping us get work done - is one of the most unnatural environments our little primate selves can find themselves in. It's a place where all the usual characteristics of the dominant animal - strength, intelligence, speed - are largely redundant, and the behaviors of the biologically weak - low cunning, obedience, surviving by finding and clinging to a protector, getting status by virtue of age - tend to be the successful strategies. As a consequence, you often find Alpha-animals being dominated by Beta (and in the case of some bosses I've suffered under, even Delta) ones. The usual primate strategies (making the loudest, fiercest display, beating up your rivals) just don't work.

As a consequence, many office workers live in a state of low-level stress all year round. Which means that the dangerous mix of booze and false equality that characterizes the office party creates a Pandora's Box for all sorts of emotions to come out. Hence the fighting and shagging.

As for your own indiscretion, the chances are that this was your amygdala up to what it does best, again. Because whatever your waking brain thinks you want in a man - education, salary, flowers 'n' poems, a nice suit - your amygdala is still back there in the jungle fighting tooth and claw for survival. As far as your amygdala was concerned, you hooked up with the Alpha-est male in the room.

Office parties shouldn't be an ordeal, as long as you keep your head. This year, just pretend to drink. Well, after you've had a couple to loosen up your sense of humor, anyway. The reward will be the relentless entertainment of watching your colleagues leap about baring their teeth and waving thigh-bones at each-other, like in the opening scenes of 2001: A Space Odyssey.

Read Serena's latest advice here.