Remembering how to ride a skateboard, even though it has been a few years since you were last on one, is a subtype of memory termed implicit; procedural memory procedural; state-dependent retrieval procedural; episodic memory episodic; procedural memory

implicit; procedural memory      

Explanation:

Implicit memory: This is also referred to as automatic or unconscious memory. It utilizes past experiences or memories irrespective of the time in which the experience has been occurred to remember those things without conscious awareness.

Example: An individual who has learned to ride a bicycle will be able to ride even after years of not riding.

Procedural memory: This is a type of long-term memory and implicit memory in which a person can perform a particular task without being consciously aware of the experience of that particular task.

Example: Tying one's shoes.

the answer to your question is,

old stone age.

-mabel < 3