It reminds us that in the absence of a birth record, the legal framework in which our ancestors operated can provide important clues about their age. Knowing how old a person had to be to marry (among many things) can help us narrow the range of a search considerably.
Judy G. Russell is providing so much good information here it’s unfair to single out any one paragraph, but since this one involves my home state and really is a very good example, here goes:
In East Jersey, the 1683 Fundamental Constitutions required the ruling Proprietors to be 21 years old in order to vote (section XIII), jurors were required to be age 25 (section XIX), and whenever any names were to be drawn by lot for elections or jury service, the drawing was done by a boy under the age of 10 (sections III and XIX).
Where you find a name, and at what point in a place’s legal history, can point you to some very specific age frames, as Russell’s posts amply illustrate. Great stuff.