High Quality Content by WIKIPEDIA articles! The Older Peron transgression was a period of unusually warm climate during the Holocene Epoch. It began in the 5000 BCE to 4900 BCE era, and lasted to about 4100 BCE (different climate indices at different locations over the globe yield slightly varying chronologies). The Older Peron was a period of generally clement and balmy weather conditions that favored plant growth; in the dendrochronology of the bristlecone pine, which extends back from the modern era to 6700 BCE, the single best year for the growth of the pine was 4850 BCE, early in the Older Peron era.