Here's visual proof that us humans like to cluster in cities.
To understand the map, called "Dencity," notice that it's full of colorful circles. The areas of the planet with a lower population density have larger circles with darker colors, while the higher population densities have smaller circles with brighter colors. It's a bit counter-intuitive at first with small circles representing large populations and vice versa, but it does a good job of helping us visualize the population density of a place -- a nice reminder that we could all live comfortably in a Texas-sized city. Here's how China, the country with the world's largest city, is represented:
Contrast that with the U.S., and it's no wonder, with our unsustainable development patterns, that our total annual carbon emissions rival China's, even though we have more than 1 billion fewer people.