Currently there are approximately 6.9 billion people on earth. A conservative estimate of 4.71 billion, approximately 67%, believe in supernatural beings and forces. Here's a breakdown by religious belief:
Hinduism: .95 billion
Judaism: .13 billion
Islam: 1.3 billion
Christianity: 1.9 billion
Animism: .23 billion
Other Theisms: .2 billion
The remaining 2.19 billion, or 33%, include Buddhists and secularists such as atheists, humanists and agnostics.
Belief in supernatural beings and forces most likely began after our ancestors had invented symbolic speech and language, approximately 100,000BP. Our ancestors may have begun to think symbolically before this in that there is compelling evidence that other animals - the great apes, dogs, dolphins, and others - also think symbolically though to a lesser degree and effect than humans.
With the advent of symbolic speech and language came the attendant ability to think of and comment in detail on events in the past and present, and possible events in the future. The ability to consider and discuss these events and their possible causes and effects gave rise to numerous explanations for the origin and workings of the forces of Nature and the objects of the day and night sky. Among these explanations were the invention of supernatural forces and human-like and nonhuman-like gods.