languages change all the time. You probably speak pretty much the same as your parents did - but not exactly the same. You've picked up new words from friends, from your travels, from reading or watching television. Adam and Eve had no word for computers; their descendants have just had to make them up. From time to time, for reasons nobody quite knows, languages undergo wholesale changes in pronunciation too, just to make things trickier. All these possibilities add up - or rather, multiply up - to vast changes over the millennia during which humans have been speaking.