Last name

When did people start using last names? And why? probably I can find answers in wikipedia or history of cultural evolution. But every time I read a news article in Yahoo or in Mercury news, whenever they mention a name from a country where having a last name is neither a cultural thing or a social necessity, they say ----, "who goes by one name only" . What is the significance to the readers to know if the person has "one name only?". Is it some way of putting down the other part of the world where people always have just the given name and live just fine and happy as everyone else?

I see all kind of funny last names - Winehouse is for example is a last name of a celebrity. Sometimes the meaning makes me laugh. But I still do not understand why the so called very important news organizations like AP or Reuters, when reporting even a serious news item, pause to mention "goes by one name only".