Researchers discover strange periodicities in history

Two Slovak researchers have published several papers in recent years in which they suggest that in history there are statistically significant cycles of about 500 years in which emerge great poets, historians and physicians, and occur periods of political instability and chaos.

http://www.sophia.sk/sites/default/files/Ancient-poets.pdf (poets)
http://www.sophia.sk/sites/default/files/Ancient-historians.pdf (historians)
http://www.sophia.sk/sites/default/files/Ancient-physicians.pdf (physicians)
http://www.sophia.sk/sites/default/files/Egyptian-dynasties.pdf (political chaos)

The first and fourth papers were published in the peer-reviewed journal Neuroendocrinology Letters and the first paper also won an award from this journal and from Charles University in Prague (http://www.sophia.sk/sites/default/files/Zdenek_Klein_Award_2004_0.pdf).

The lists of great poets, historians and physicians were taken from anthropologist Kroeber's book "Configurations of Culture Growth". Political chaos was statistically analyzed on durations of Egyptian dynasties, data taken from egyptologists Baines and Shaw.

In all four papers, the discovered 500-year cycles seem to be roughly synchronous in different parts of the world, therefore the authors think that the causative factors are global, rather than local. They mention that ancient Babylonian priests predicted these 500-year cycles and attributed them to their gods.