a word about whistling

I was standing in the gentleman's toilets the other day when a question popped into my head. Why do men whistle more than women? (according to research, there are only 2 women in the world that whistle, and they both live in Eastern Russia) I find that the most common time to hear examples of whistling is in the toilet. I suppose that I must have heard someone whistling to put the thought in my head. When one thinks of whistling in terms of a carefully executed exhalation of air, and positioning of the lips to provide "tunefullness", much like singing, it poses another question: most people (let alone men) would be too shy to sing in public, so why, therefore, should whistling be any different? It is, in fact, very expressive. Should men really be happy with this?

What I can say is that I think i've identified two main types of whistling, which are defined by the situation in which they are used. There is the "fake" whistle, presumably to mask an uncomfortable situation, and often heard in the toilet (or perhaps after an embarrassing slip of some sort), which is often simple and repetitive in style (after all it's only a decoy), and there is the "whistle of contentment", often heard used by old men while looking at house plants (but not exclusively so), which can be extremely intricate in style and is, I think, a genuine expression of happiness with the world.

Ok, so I may have identified different types of whistling but this doesn't answer my initial question: Why do men whistle more than women? Is it a vent for stress? something used instead of talking through feelings? Or it could be a way of expressing excitement - how often do you hear a man expressing his excitment about something in words? Or perhaps it goes back to the dawn of man - something to do with mating, attracting attention, or hunting for food... an instinct which can't be shaken off? Who knows. I would love to know the reason. Yet another of life's little mysteries... suggestions are welcome.