Origin of serrations?

[Dan Hibiki]

Does anyone know what the first bladed weapon purposefully designed to have serrations was? I say purposefully because while stone spearheads were serrated, I an not convinced that primitive spearhead-making techniques allowed any other edge

I guess while you're at it you can point out some points in history were serrations made a big difference in warfare (if any).

Thanks!

=- Curious Craig