You may remember Cosmos, the 1980 PBS series by Carl Sagan. Maybe you also recall Sagan’s “Cosmic Calendar” from the series, where in order to put the immensely vast history of the universe into a comprehensible scale, he mapped it onto a calendar year. In other words, if the entire history of the universe were one year, with the big bang in the first second of midnight on January first, and the present day on the last second of December 31st, New Year’s Eve. A project of mine this year has been to note the major events in the Cosmic Calendar, on the real calendar, on this blog!
December 15th on the Cosmic Calendar: The Cambrian Explosion! Before the Cambrian period, while there were a few multicellular animals, most were still single-celled. When they felt ambitious, they might build a stromatolite. Just before and at the beginning of the Cambrian, something — we yet know not what — kicked evolution into high gear and a variety of animals and other organisms appeared similar to the number of species we have today. They were almost all different animals than we see today — now they’re mostly if not all extinct — but there was a similar variety as in the present. This development is what is referred to as the Cambrian explosion. The Earth was finally populated with life in similar numbers to how it is today.
I painted the Cambrian Explosion once. It’s still one of my favorites of my paintings.
Those are my impressions anyway. It really looked more like this: