530 Million B.C.T. - The Cambrian Explosion

Around 530 Million B.C.T., the Cambrian Explosion began.

The Cambrian explosion, or Cambrian radiation, was the relatively rapid appearance, around 530 million years ago, of most major animal phyla, as demonstrated in the fossil record, accompanied by major diversification of organisms including animals, phytoplankton, and calcimicrobes. Before about 580 million years ago, most organisms were simple, composed of individual cells occasionally organized into colonies. Over the following 70 or 80 million years, the rate of evolution accelerated by an order of magnitude (as defined in terms of the extinction and origination rate of species) and the diversity of life began to resemble that of today.


The Cambrian explosion has generated extensive scientific debate. The seemingly rapid appearance of fossils in the “Primordial Strata” was noted as early as the 1840s, and in 1859 Charles Darwin discussed it as one of the main objections that could be made against his theory of evolution by natural selection. The long-running puzzlement about the appearance of the Cambrian fauna, seemingly abruptly and from nowhere, centers on three key points: whether there really was a mass diversification of complex organisms over a relatively short period of time during the early Cambrian; what might have caused such rapid change; and what it would imply about the origin and evolution of animals. Interpretation is difficult due to a limited supply of evidence, based mainly on an incomplete fossil record and chemical signatures remaining in Cambrian rocks.

The Cambrian Explosion -- Earth's evolutionary equivalent to the "Big Bang" -- began some 530 million years ago.  Within the span of a mere 5 million years, the ancestors of almost all animals suddenly appeared on the Earth.  There have been a number of theories advanced concerning the reasons for this "creative" explosion.  Some have said that an increase in the Earth's oxygen supply fueled the outburst.  Others say that a decrease in carbon dioxide in the Earth's atmosphere led to mass "creation."

One of the more intriguing theories for the species explosion is that the evolution of eyes sparked the Cambrian "Big Bang."  According to this theory, before the eye came along, there were just simple animals -- essentially just worms and jellyfish.  However, once the evolution of the eye came along, massive natural selection pressures began to exert themselves forcing these simple life forms to alter themselves for purposes of protection and reproduction.  These alterations led to life forms learning how to swim, burrow, hide, have armored body parts or reflect warning colors.  And it was these adaptations that eventually led to our diversity of life.

At least, that is the theory.