🌍 When, and above all how, did life evolve on our planet? This existential question, which we all ask ourselves at one time or another, animates scientific communities the world over. To answer it, paleontologists have no choice but to uncover fossils and study them at length, in order to date them and exploit the extensive data collected. While certain periods in the history of our distant past are beginning to provide some clues, one in particular stands out from all the rest, so exceptional does it seem.
We're going to take a very close look at one of the most famous and important eras in the history of the Earth, and of life in particular. This is the Cambrian period. This phase of history marks the appearance of the first ancestors of the plant world, but above all, represents the dawn of the Paleozoic era, with the appearance of living beings that still exist today.
Transported more than 500 million years into the past, our journey through time takes us to a time when the land was rocky and desolate, but the oceans were inhabited by mind-boggling creatures. This period in Earth's history saw the sudden appearance of almost every major form of animal life, in a short period that is thought to have lasted around 25 million years. Scientists call this explosion of life the Cambrian Explosion. This event, unique on the time scale, was therefore of paramount importance for the occurrence and development of life as we know it today.
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💥 Cambrian Era:
- More than 3.9 billion years have passed since the formation of planet Earth. The Precambrian phase, which successively encompasses the Hadean, Archean and Proterozoic eons, was marked by the formation of the oceans, the cooling of the Earth and the solidification of its crust, followed by the formation of the continents Columbia and Rodinia. But it also witnessed the appearance of life in the form of bacteria, then later, during the Neoproterozoic era, the appearance of the Ediacaran marine fauna, with archaic organisms, but above all the bilaterian metazoans.
The Cambrian thus follows this first, long period of almost 4 billion years. This is the first era of a long series that makes up the Phanerozoic Eon, which extends to the present day, itself divided into four sub-categories. The first corresponds to the Paleozoic Eon, or Primary Era, beginning with the Cambrian. The second sub-category is the Mesozoic, or secondary era. Then follows the Tertiary and finally the Quaternary eras, grouped together under the Cenozoic eon, which saw the appearance of the first primates and the evolution of many species as we know them today.
But let's return to the period we're interested in, the starting point of the Paleozoic era: the Cambrian period. Spanning the period from 541 to 485 million years ago, this is the oldest of the six Paleozoic periods. What happened during these 56 million years that marked a decisive turning point, to the point of being defined as the starting point of a new and one of the greatest divisions of geological time, namely the Phanerozoic Eon?
But what might the planet have looked like during the Cambrian period, which marks the beginning of the Lower Paleozoic? During the Pre-Cambrian Eon, Rodinia was a megacontinent that brought together all the continental masses. Under the influence of plate tectonics, it gradually fragmented. Pieces of continental crust began to drift away across the vastness of the oceans.
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🎬 Today's program:
00:00 - Introduction
02:57 - The Cambrian: a geological era
10:01 - The continents of the Cambrian era
14:05 - Climate in Cambrian times
17:17 - The Cambrian Explosion
22:43 - Cambrian in the world
24:48 - Burgess Shales
50:19 - Chengjiang fauna
57:25 - Tomotian fauna
01:00:36 - Titanokorys gainesi
01:04:09 - First food chains
01:11:02 - The Cambrian ecological revolution
01:14:13 - Cambrian-Ordovician extinction
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