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.
Recent studies have also emphasized the abruptness of the Cambrian explosion. phyla was unlikely to have exceeded 10 million years (Excerpt D, p. 1297). the base of the Cambrian to the present day (Excerpt E, p. 852). Earth, this means the Cambrian explosion was geologically very abrupt, indeed.