Would a "new" soul even ask such a question?
I don't know what to think about these "soul age" theories anyway, but in my opinion you will need a certain "level" of "development" before you even begin to ask such questions, get seriously interested in spiritual topics and want more from life than just the usual like what your society defines as "success", material wealth, safety, fulfillment of desires and whatnot.
Of course, there may be people who are interested in reincarnation and soul age because they hope for an ego booster, but I would assume that most people who come here (with very few exceptions, and those people usually vanish after a short time) are at least what usually is referred to as "mature" soul.