Once you realize that you have a favorite historian, you have probably already realized how much of a geek you are. I have several like Doris Kearns Goodwin, Barbara Tuchman, David McCullough and Thomas Cahill. But the most intrigue of them, I believe is Jared Diamond. Diamond likes to write about long term issues like why do some cultures or civilization survives and other don't. Some cultures simply disappear in history while others flourish. One of things he points out is how the Old World (Europe and Asia) had many domesticatable animals while the New World (America and Australia) did not. This allowed for speedier advancement and faster growing populations. Some animals in the new world and Africa are just not domesticatable , like the buffalo and the zebra, no matter how hard you try.
What I learned today is that this didn't occur naturally but that in many parts of the planet, the domesticatable animals did exist but were simply hunted to extinction. The term for this is the New World Blitzkrieg.