Why Map.containsKey() takes an Object parameter instead of a speciallized type?

Possible Duplicate:
What are the reasons why Map.get(Object key) is not (fully) generic
Java Generics: Why Does Map.get() Ignore Type?

Java Map interface is declared like this:

Interface Map<K,V>

It has such a method:

boolean containsKey(Object key)

Why not boolean containsKey(K key)?

On the contrary, the List interface has add method that takes parameter of generic type instead of Object:

boolean add(E e).