a study led by researchers at the Nagoya University Museum in Japan may change how we understand the cultural evolution of Homo sapiens at the time of their dispersal across Eurasia about 50,000 to 40,000 years ago . These findings challenge traditional beliefs about the timing and nature of cultural transitions during this critical period in human history . The researchers examined the productivity of stone-tools with a cutting-edge over a 50,000-year span that encompassed six cultural phases .