2C; A Global Perspective
500 Million Years Ago
When Georgia’s trilobites lived during the Middle Cambrian Period, more than 500 million years ago, Georgia was the floor of a shallow sea and there were no bones, trees, insects or enameled teeth (such as ours) on all the Earth.
Vertebrates were as yet unknown; simple chordates, which would lead to vertebrates, had just emerged in the Cambrian Explosion and were present in a very basic form. A skull-like structure was present, though jawless, and a hollow tube of cartilage serving to protect their notochord (see: Haikouichthys). However, the earliest vertebrates; fish, would soon appear.
Simple marine plants were present, but landscapes were barren of green life. Biological films and micro biological mats could be found in tidal flats and perhaps beaches. Inland there were only lichens and fungi.
The Appalachian Mountains, one of the oldest mountain ranges in the world today, was still hundreds of millions of years in the future. Georgia was even in a different place, due to plate tectonics (continental drift) it was deep in the Southern Hemisphere.
Cambrian Explosion
All modern advanced life can be traced back to the Cambrian Explosion. The term Cambrian Explosion was coined by Stephen Jay Gould (1941-2002) and occurred roughly from 530-520 million years ago. Multi-celled life diversified and radiated wildly, setting many basic patterns which would endure and eventually lead to the forms we see today, including us.
Primitive life on Earth can be confidently traced back to 3.5 billion years ago, right to the point where the Earth had stabilized enough to support large bodies of standing water.
From 3.5 billion years ago to about 700 million years ago, research suggests that only single celled life was present. At about 700 million years ago we see evidence for small, simple multicellular life. Then the Cambrian Explosion of advanced life occurred.
Primitive life on Earth can be confidently traced back to 3.5 billion years ago, right to the point where the Earth had stabilized enough to support large bodies of standing water.
From 3.5 billion years ago to about 700 million years ago, research suggests that only single celled life was present. At about 700 million years ago we see evidence for small, simple multicellular life. At 530 million years ago advanced life emerged and expanded wildly; this is the Cambrian Explosion of life.
Charles Darwin is famous for his work on evolution. Darwin was essentially an amateur researcher with no formal scientific training; his “ordinary” degree was geared towards becoming a parson, or preacher.
He was intensely interested in nature; fortunately for us he came from a wealthy background. Also, fortunately for us, he lived in a day when the study of nature was considered a worthy and prestigious pastime for gentlemen of wealth. (Darwin could never be described as a gentleman of leisure.)
Darwin didn’t discover evolution; the theory was well known long before his time, but no one could see how evolution worked. Darwin discovered Natural Selection; this is the theory that nature challenges each individual’s capabilities and those which possess an advantage, no matter how small, tend to be more successful.
Darwin was looking at how species emerge, or where they come from; he was looking for the origins of species. He didn’t find it. What he did find and define was descent with modification. He saw that Natural Selection has been active since the beginning of life. His theory does not address the origins of life, rather why and how it diversified afterwards.
Evolution operates on the level of the individual. Individuals who possess some advantage, no matter how small, tend to produce more offspring.
If this advantage is genetic, the advantage gets passed to following generations.
Advantages tend to be naturally amplified in successive generations; (what creates success in one generation usually creates success in later generations) thus we have descent with modification.
The Cambrian Explosion was triggered by a wealth of simplicity. When the most advanced life forms are simple multicellular animals and plants, a single predator with a minimum of adaptations, becomes a terror feeding freely on the hordes.
Evolution operates on the level of the individual. Individuals who possess some advantage, no matter how small, tend to produce more offspring.
If this advantage is genetic, the advantage gets passed to following generations.
Advantages tend to be naturally amplified in successive generations; (what creates success in one generation usually creates success in later generations) thus we have descent with modification.
The Cambrian Explosion was triggered by a wealth of simplicity. When the most advanced life forms are simple multicellular animals and plants, a single predator with a minimum of adaptations, becomes a terror feeding freely on the hordes.
An arms and defense race ensued; any defensive adaptation which provided some protection from predators was amplified. Any offensive adaptation which allowed greater feeding opportunities was amplified.
All of this began in the world’s oceans, a big place with a wealth of environments and very little isolation.
For a period evolution drove a level of change never before seen on planet Earth, this is the Cambrian Explosion.
And since the only advanced life on Earth was in the seas all of that change quickly spread globally. What we are today began during the radiation of new species in the Cambrian Explosion.
At about 510 million years ago the first plants colonized land, but these were very simple organisms unable to survive far from water. By 400 million years ago plants had developed their familiar roots, leaves and woody branches. By 360 million years ago seeds had emerged and forests of tall trees were present. The first flowering plants (angiosperms) didn’t emerge until about 140 million years ago and began to replace the more primitive conifers in most environments around 100 million years ago.