Historically, Poland has been part of the barrier against the steppe invassions, first the Mongols, then the Russians themselves. From that point of view, it would be central Europe, as the steppe peoples would be eastern Europe. Poles often lived within the HRE, which would place them squarely in the Mittel-europa.
The Cambrian Explosion refers to the metaphorical explosion of life that began 542 million years ago and lasted for roughly 40 million years. This lesson will cover the events that occurred during this time period.
The Cambrian spans from 541 million years to 485 million years and is the first period of the Paleozoic Era of the Phanerozoic Eon. The Cambrian marked a boom in evolution in an event known as the Cambrian Explosion in which the largest number of creatures evolved in any single period of the history of the Earth.