The Vendian

650 to 543 Million Years Ago the latest part of the Proterozoic

This is the time when the earliest-known animals evolved, and the continents had merged into a single super continent called Rodinia.  Simple primitive life is known from 3.5 billion years ago. Why did it take so long for complex life to evolve and what kick started this development?  One interesting idea is called Ice Planet Earth.  The planet froze over completely, isolating the remaining life into pockets and subjecting them to extreme conditions.  Eventually, the ice melted and the combination of events proved to an evolutionary stimulus.  The Ediacara fauna marks the beginning of visible life; including soft-bodied multi-cellular animals, like sponges, jellyfish, worms, and relatives of the arthropods. Just what if any is the relationship of these strange animals to modern animals is debated.  There are two basic ideas; one being that the fauna dominated by animals with a thin quilted construction died out as a failed experiment.  The thin quilted body plan could have allowed them to breath without developing complex internal structures. There don't seem to be any carnivores so they may have been especially vulnerable as predators evolved.  The other camp sees them as predecessors to the animals seen later in the Cambrian.  Fossils are rare and usually difficult to interpret, but as more finds come to light I expect a synthesis of the two views will arise.  The Ediacara was named for the Ediacara Hills in Australia, north of Adelaide; the most famous Vendian fossil deposit.

updated 050612