🏆Best of Crash Course: Our very first Crash Course video, The Agricultural Revolution: Crash Course World History, is one of the most beloved. This opening sequence about the importance of learning encapsulates why we do what we do! To see that it resonates with so many of you as well never ceases to warm our hearts! Watch the full video for another all-star Crash Course clip "the journey of a double cheeseburger" https://youtu.be/Yocja_N5s1I | CrashCourse

Genetic drift happens when chance events cause alleles to spike or decline from one generation to the next. Sometimes a segment of a population gets isolated and continues to grow and mutate on it's own. Sometimes populations change as a result of natural disasters or human intervention. https://youtu.be/mFvmY9JASO4 | CrashCourse