[fruser1]

There were not 4 ice ages in the last 500k years.

There were 4 GLACIATIONS (where ice advances).

We are currently in an ice age that is 4 million years old.

There have been 60 glaciations in that time period.

http://www.museum.state.il.us/exhibits/ice_ages/when_ice_ages.html

[SunkenCiv]

Thanks fruser1.