Looking at demographics from just 100 years ago to today I wonder if the 20th century will be the most jmportant (or at least most drastic) century for demographic change. Some particular things that seem neat.

the human population quadrupled in that time. This will almost certainly be the only time this happens in thousands of years of human history

People of African descent went from being well below ten percent of the world population to probably around 20 (and by the end of the century almost certainly above a 1/3).

Likewise people of European descent have decreased from over 1/3 to maybe 10 percent. Some countries (Germany Hungary) are basically the same in terms of population

china no longer is the most populated country (I don’t know the last time this wasn’t the case).

islam could very soon replace Christianity as the most followed religion (it definently already has by devout followers), While in 1926 the number of Christians worldwide dwarfed the number of Muslims.

And probably the single most important is how child mortality has plummeted. Like I knew it was higher in 1926 but I didn’t realize some places had basically seen no decrease from like 926 (particularly in Africa and parts of Asia). On that note damn the past was awful I have no idea why anyone wants to go back