Overloading methods in R

(1) It seems to me that, generally, in R it is not possible to  
overload functions. Is that right?

(2) Assuming that the above is true, or partially true, is there any  
extra packages to handle overloading in R?

(3) Assuming (1) is TRUE and (2) is FALSE, can anyone provide some  
advice on developing some function that understand what the arguments  
are and then calls the right overloaded function?

It would be something like this:

overloadedFunction1 <- function(x) {};

overloadedFunction2 <- function(x, y) {};

theFunction <- function(...)
{
  # How to identify ... and call the right overloaded function?
}