Answer
Bone Age is not part of Gimbutas' three-age system, which is a periodization scheme for European prehistory. Gimbutas' system is based on archaeological finds and cultural changes and divides prehistory into three main ages: the Stone Age, the Bronze Age, and the Iron Age. Bone Age, on the other hand, is a concept used in forensic anthropology and paleopathology to estimate the age of an individual based on skeletal development.