This is mentioned in the first Crash Course World History video. https://www.youtube.com/watch?v=Yocja_N5s1I&list=PLBDA2E52FB1EF80C9 https://www.youtube.com/wa

This is mentioned in the first Crash Course World History video. https://www.youtube.com/watch?v=Yocja_N5s1I&list=PLBDA2E52FB1EF80C9 https://www.youtube.com/watch?v=Yocja_N5s1I&list=PLBDA2E52FB...