During the time period of ancient history (starting roughly from 3000 BC), the world population was already exponentially increasing due to the Neolithic Revolution, which was in full progress. According to HYDE estimates from the Netherlands, world population increased exponentially in this period. In 10,000 BC in prehistory, the world population had stood at 2 million, rising to 45 million by 3,000 BC. By the rise of the Iron Age in 1,000 BC, the population had risen to 72 million. By the end of the period in 500 AD, the world population is thought to have stood at 209 million. In 3,500 years, the world population increased by 100 times.