It's certainly some kind of idol, but my theories would be more along the lines of it representing a hero of some kind. It's quite common for factors to be exaggerated to almost inhuman proportions, which would also explain why the figure seems to be carrying a weapon of some sort.
...Of course, heroes could become fertility idols too, if they were particularly... potent in that department... maybe it all loops around. The past is a confusing place.