Göran Burenhult's data in chapter 8 suggests that human migration to North America happened about 15,000 years ago. New research suggests that this migration may have occurred 6,000 years earlier: https://www.nbcnews.com/science/science-news/fossil-footprints-show-humans-north-america-21000-years-ago-rcna2169 . Here is a link to the journal article: https://www.science.org/doi/10.1126/science.abg7586.