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.
View full size image. The Cambrian Period is the first geological time period of the Paleozoic Era (the âtime of ancient lifeâ). This period lasted about 53 million years and marked a dramatic burst of evolutionary changes in life on Earth, known as the Cambrian Explosion..