lived near the close of the “Cambrian Explosion
”. The Cambrian Explosion refers to the sudden appearance in the fossil record of complex animals. It may represent the most important evolutionary event in the history of life on Earth.
The beginning of the “Explosion” is generally placed about 542 million years ago, during the Cambrian Period at the start of the Palaeozoic Era. The Burgess Shale, at 505 million years old, records the tail end of this event. By the end of the Cambrian, every major animal phylum (i.e. different body plans) was firmly established, and life after the Cambrian was radically different from what had gone before. So it is safe to call this event an "Explosion" - it was crucial to the evolution of life on Earth as we know it.
Why did the Cambrian Explosion happen when it did, and why was it such a unique event? While there is no current consensus among scientists, most researchers agree the Explosion cannot be ascribed to a single, simple mechanism. The potential triggers can be classified in three main categories: environmental, genetic, and ecological. Deciphering the impact of each of these factors remains one of the most important challenges faced by palaeontologists today. For more information on the triggers of the Cambrian Explosion, click here
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