Final answer:
The refitting of studies of flakes suggests that humans in the Upper Paleolithic period shifted from the manufacture of round flakes to the manufacture of blade tools, which were more efficient.
Step-by-step explanation:
The refitting of studies of flakes suggests that humans in the Upper Paleolithic period shifted from the manufacture of round flakes to the manufacture of blade tools. This construction method, known as the blade tool industry, involved creating long, thin, and flat stone flakes with sharp edges. Blades had a longer cutting edge than flakes and were more efficient. The refitting of studies of flakes provides evidence of this technological advancement in human tool making.