Until the 1800s, population growth was incredibly slow on a global level. The global population was estimated to have been around 188 million people in the year 1CE, and did not reach one billion until around 1803. However, since the 1800s, a phenomenon known as the demographic transition has seen population growth skyrocket, reaching eight billion people in 2023, and this is expected to peak at over 10 billion in the 2080s.

The earliest point where scientists can make reasonable estimates for the population of global regions is around 10,000 years before the Common Era (or 12,000 years ago). Estimates suggest that Asia has consistently been the most populated continent, and the least populated continent has generally been Oceania (although it was more heavily populated than areas such as North America in very early years). Population growth was very slow, but an increase can be observed between most of the given time periods. There were, however, dips in population due to pandemics, the most notable of these being the impact of plague in Eurasia in the 14th century, and the impact of European contact with the indigenous populations of the Americas after 1492, where it took almost four centuries for the population of Latin America to return to its pre-1500 level. The world's population first reached one billion people in 1803, which also coincided with a spike in population growth, due to the onset of the demographic transition. This wave of growth first spread across the most industrially developed countries in the 19th century, and the correlation between demographic development and industrial or economic maturity continued until today, with Africa being the final major region to begin its transition in the late-1900s.

The largest Western European city in 1200 was Palermo, with 150 thousand inhabitants. This is a great decrease in the number 150 years previously, where the population was 350 thousand. The city of Cordova also decreased by almost 400 thousand in this time, possibly because of the declining Arabian control and influence in the area. Seville is the third largest city on this list, although it's overall population decreased by ten thousand since 1050. The largest cities are generally in Spain or Italy, although the second largest city on this list is Paris, with 110 thousand inhabitants. In the lists that follow, Paris remains at the top as either the largest (1500 and 1650) or second largest (1330 and 1800) city in Western Europe.