China and India are the most populated countries in the world. Above, the Hong Kong skyline. Pixabay, public domain

China and India are the only countries in the world with populations that have cracked a billion. It might be the land all those people live on that have made their nations so prolific.

China’s population is almost 1.4 billion and India’s is just above 1.3 billion. MinuteEarth points out in a new video that together they have more people than the next 20 of the world’s most populated countries — combined. Add those two groups to the populations of all the other nations and you arrive at the world’s 7.5 billion total.

The two Asian countries at the top added more to their population than anywhere else over the last three centuries, but the math shows they were growing at the same rate as the others.

“They have a lot more people today because they had a lot more people a few hundred years ago when the world began a period of modern and rapid population growth,” MinuteEarth narrator Kate Yoshida explains.

Although things like medical advancements, natural disasters and war all play a role in population growth, MinuteEarth asserts that agriculture had the greatest influence over their sizes.

“Having lots of fertile land and good access to fresh water makes it possible to grow lots of food, which in turn makes it possible to nourish a lot of people,” according to the video.

In Asia there is a lot of arable land and farmers can grow their crops year-round. There is also a long history of livestock domestication on that continent. In the case of China and India specifically, both countries cover an enormous area, so they have potential to hold way more people than smaller Asian countries.

It’s no coincidence that in the group of the world’s most populated countries, many have space in the millions of square kilometers. The further you go down the list, toward the lesser populated nations, the more infrequent it is to see a country with a square-kilometer measurement in the seven digits.

Agriculture and open space came together to give China and India a boost, MinuteEarth says. “When the era of modern population growth came around, they had a head-start.”