<human>:  Why did the population of the Roman Empire fall?
<bot>: The population of the Roman Empire fell because of a combination of wars, disease, and famine. The population of the Roman Empire peaked around 50 million people in the early 1st century AD, and then began to decline due to a combination of factors. The population was reduced by half during the 3rd century, and fell to around 20 million by the 6th century.