During the time of the Roman Empire, Western Europe, India,and China had the ruling populations with a few million each. Nearly 1250 years later during the time of Mongols in China, the ruling populations were in all of Europe, India, China, and Japan. Sixty years later, there was a major drop in Europe's population, due to the Black Plague(or Black Death). By the time of the Industrial Age, Europe's population had rebuilt itself. In the time of the World Wars, America, Europe, India, China, and Africa had the largest populations. Moving on to modern times, all of the continents have billions of people, but the leading countries are China and India, as they were 2000 years ago.
This topic was if interest to me because I have always found it incredibly crazy that there are billions of people on such an incredibly small planet(that is, when you compare it to the universe!). The growth of the human population over a two thousand year has gone from a few million to over seven billion.
I can't connect this to my life in very many ways, but when I was in third grade, I began to take interest in the growth of the butterfly population in my grandmother's backyard. Two years after I started to take attention to this, I noticed that there was an increase in the population. Though, since then, the population has seemed to decrease, for an unknown reason.