Long bone epiphyseal fusion — the joining of the growing ends of long bones to their shafts — occurs at predictable ages and provides a minimum age indicator: if all growth plates are fused, the individual had reached skeletal maturity.

Joint surface wear — the gradual development of arthritic changes on weight-bearing joint surfaces — provides an upper indicator of age, with more extensive changes generally associated with greater age.

The combination of these indicators typically produces an age range rather than a specific year.

The determination that the Hourglass Cave man was roughly 35 to 45 years old at death reflects this range.

He had clearly passed skeletal maturity — he was not an adolescent or young adult — and the degree of age-related change in his joint surfaces was consistent with middle age rather than advanced age.