Our planet is crowded with a spectacular diversity of living creatures. As a most peculiar fact, the oldest of these are in general the most primitive whereas the most recent are the most advanced. How can evolution be working in order to bring about such a counterintuitive result? This raises the challenging question of a direction of evolution. Is it proceeding in a certain direction, is it improving, is it even accelerating?

By introducing the concept of complexity, the author suggests a new way of describing the process of evolution. In this conception, the human cultural evolution...