<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 Roman Empire was conquered by the Germanic tribes in the 5th century AD, which caused the population of the Roman Empire to decrease. In addition, the plague epidemic of the 6th century AD, which killed about half of the population of the Roman Empire, also contributed to the population decline.