It's all pants to me

So this morning I went swimming, and in a hazed state (mainly because I hadn’t had any tea yet), I forgot my underpants. So back home I went, bare bummed, with just a pair of jeans. And that got me thinking, who decided that we need an extra layer underneath our clothes? Scotsmen don’t have them when they wear kilts, some lovely ladies don’t wear them under their skirts and most people only wear vests in the extreme winter. So what is the necessity of wearing modern pants? Is it just a bit of warmth in the winter and we should all throw them out alongside our summer vests? It gets even more confusing when Americans refer to trousers as pants. And then you have the uber-cool people, who think that it’s confused to wear their underpants sticking out over their trousers. Clearly the world is very confused with the modern purpose of pants, and the warmer it gets, the skimpier we dress.