Precambrian

The Precambrian (PROSE: Prehistory Repeating Itself ^[+]Loading...["Prehistory Repeating Itself (feature)"], The Myriapod Mutiny ^[+]Loading...["The Myriapod Mutiny (short story)"]) also spelled pre-Cambrian, (PROSE: Deceit ^[+]Loading...["Deceit (novel)"], Blood Heat ^[+]Loading...["Blood Heat (novel)"]) was a period of Earth history which spanned from 4.5 billion to 542 million BCE, when animals first evolved and the Cambrian period began. The Precambrian accounted for 87% of Earth's history as of the 21st century.

Life evolved during the Precambrian, but consisted of only single-celled organisms and bacteria for billions of years. There were no plants, no animals, nothing but microscopic creatures. These tiny organisms were responsible for the biggest change in Earth's atmosphere; through photosynthesis, they added oxygen to the planet's atmosphere, making it possible for larger, more complex life to evolve. The oxygen catastrophe wiped out much of the existing life on Earth that could not tolerate the new oxygen-rich conditions. From the perspective of 21st century humanity, a creature or disease from the Precambrian would be as incomprehensible and bizarre, and potentially as dangerous, as an alien. (PROSE: Prehistory Repeating Itself ^[+]Loading...["Prehistory Repeating Itself (feature)"])