Simplify the following text for a Grade 12 native English-speaking person.
Original: The hypothesis suggests that the speakers of the Proto-Indo-European language ( PIE ) lived in Anatolia during the Neolithic era , and associates the distribution of historical Indo-European languages with the expansion during the Neolithic revolution during the seventh and sixth millennia BC .
Simplified: The Anatolian hypothesis of Proto-Indo-European origin is that the speakers of the Proto-Indo-European language lived in Anatolia during the Neolithic era . When the Neolithic Revolution took place in the seventh and sixth millennia BC , the speakers spread over Europe .