At the end of the last ice age, two worldwide changes coincided to create a small number of regions in which farming began to look tempting. First, climates began to get warmer and wetter around the globe; second, foragers now occupied so much of the Earth that some regions were beginning to feel overpopulated. Both changes nudged humans toward farming. Because these changes were felt to some degree in different regions in all of the world zones, they help explain the strange fact that farming appeared within just a few thousand years in parts of the world that had no contact with one another.
