Well the stone age is divided into 3 sub-ages:
The Paleolithic
The Mesolithic, and
The Neolithic
I just put them all together for the sake of argument.
Well, yes, but I believe you missed MP-Ryan's point here. The Paleolithic is further divided into 3 main subgroups, each of which has it's own subgroups. The Paleolithic lasted for over two and a half million years. The big historical time periods after it were each a lot shorter - probably not an exact exponential curve, but I'd have to look into it. At any rate, MP-Ryan's point here was that the modern ages last exceedingly short compared to the old ages. Whether or not the Paleolithic was subdivided into subgroups has really no bearing on his argument.
In general, humanity's historical ages are marked by technological progress, which doesn't advance in a straight curve. You get a long period of the same ol' same ol', followed by some technological breakthrough that allows a "boom" of sorts, and many of that period's advancements merely tag along on this basic new technology that was discovered. The difference to the old ages is, it no longer takes millenia between two distinct "periods". I would call some period a distinct historical age based on whether or not the lifestyles of people are vastly different to previous eras due to technology available. Based on this, I would call this age the age of communication; our internet, email, cell phone enabled every day routine made the modern way of life completely different to what it was just 30-40 years ago; a far cry from millions of year's worth of roughly similar lifestyles.