If you trace the history and pre-history of life on earth, you can see the creative process at work. Life on this planet looks and ore and more like a work in progress.
Pre Cambrian (4 million years ago)
The Pre Cambrian is the longest of the recorded geographical time periods. It covers the formation of the earth to the very beginning of life. The fossil record of this period is very sketchy as early life forms were very delicate in structure. This time period is further divided into:
>The Archeon Eon (4600-2500 million years ago)
During this time the earth is formed – a hot, volcanic and turbulent place. It is believed that during this eon, earth collided with another large body, which led to the formation of the moon. The moon helped to stabilise earth, and created tides and oceans. The oldest signs of life from this time are chemical signatures in Greenland rocks, about 3850 million years old.
>Proterozoic Eon (2500 million-543 million years ago)
This eon saw the development of simple bacteria, the earth’s most successful and persistent life form, to more complex plants and animals. At the start of this eon, life was still in the ocean – the surface could not support life, being too full of carbon, with too little oxygen. But as bacterial activity quickened up in the sea, so more oxygen was formed in the atmosphere. More complex single celled organisms (called eukaryotes) appeared about 1500 million years ago. These organisms had a nucleus that contained DNA. Between 760-600 million years ago, tempteratures dropped to -40c, creating earth’s first Ice Age. 600 million years ago, the fossil record starts to show very simple life forms.
Palaeozoic Era
The name of this era means `Ancient Life”
>Cambrian Period (543-490 million years ago)
In this era, fossils of trilobites and other shelled animals are found. But the land is still barren and hostile, so life remains in the ocean. However, evolution has produced the complex eye in some creatures.
>Ordovician Period (490-443 million years)
The ocean teems with life – there are corals, urchins, soft and hardshelled animals, and some scary creatures like giant scorpions (BrontoScorpio) who crawl onto land for brief periods.
>Silurian Period (443-417 million years ago)
Life is established on shore at the end of this period, with plants, fungi, and large arthropods, such as giant spiders.
>Devonian Period (417-354 million years ago)
This is a time of major evolutionary leaps – plant life becomes lush and well established on land, and taller plants, the fore runners of trees, start to appear. Life on land still consists mainly of insects, but the first fish now move onto land and develop lungs and legs. Possibly this is because the ocean is even more hostile now, with giant sharks.
>Carboniferous Period (354-290 million years)
As the name suggests, plants flourished in a hot, humid greenhouse climate. Earth’s crust was covered in forests of ferns from pole to pole. Trees start to grow very tall, but are still fernlike in appearance. There are still plenty of giant insects and amphibians in the oxygen rich air, and the first reptiles start to appear, laying eggs on land. But at the end of this period, around 290 million years ago, another Ice Age formed and caused many species of plants and animals to become extinct.
>Permian period (290-248 Million Years)
After the Ice Age, there is no more tropical paradise – the earth is cold and dry, with open plains and scattered thickets of ferns and conifers. Reptiles are well suited to these conditions, and began to proliferate. This period also saw the appearance of the first large land animals. Some evolved crafty ways to conserve heat for their larger bodies, such as enormous spinal `sails’ that acted as solar panels. The earth was still a turbulent place – the land masses had formed a giant continent (Pangaeia) with vast deserts caused by a lack of rain. This drought shrank the oceans toward the end of the Permian, again causing many animals to become extinct. This occurred around 248 million years ago and wiped out 95 per cent of all species alive at that time. This is the largest extinction.
Melozoic Era
This is know as the Age of the reptiles.
>Triassic period (248-206 million years ago)
The earth was left barren by the mass extinction, but a few plants survived. In the early and middle triassic, the few animals that remained had no predators and so proliferated. Evolution was accelerated during this time, with many new species appearing. Furthermore, Pangaeia began to break up, and new larger reptiles appeared. The end of this period is marked by another, smaller extinction, but it is not known what may have caused it.
Jurassic period (206-144 million years)
After the false start of the triassic, this era saw the large reptiles come into their own. Everything was right for them – a more humid atmosphere, lots of rain and flooding, all caused by the movement of the new continents. The dinosaurs and other large animals spread across the land masses, and pleisiosaurs and other water dwellers filled the oceans. With little to hinder them, the land and sea creatures grew gigantic.
>Cretaceous Period (144-65 million years ago)
The late Jurassic was pleasant, with flowering plants starting to evolve, but the cretaceous was Eden-like. But every Eden attracts danger – in this case, the freely roaming herds of huge herbivores spurred the rise of terrible predators, such as T-Rex and raptors. However it was not to last – at the end of the Cretaceous, another mass extinction wiped out both predators and prey, 40 per cent of the earth’s species. This extinction is believed to have been caused by an asteroid.
Cenozoic Era
This is known as the Age of Beasts. The last extinction wiped out the huge dinosaurs and their kin, leaving the land and sea to the smaller animals. Because the continents had drifted apart, animals now started to specialise in their local areas.
>Paleocene Epoch (65-55 million nyears ago)
Now the earth grew humid again, with jungles and swamps over most continents, and birds became the dominant species, with predators like gastornis. However, the end of the reptiles made way for the mammals to explode into the gaps, with many new species appearing and mammals we know today (elephants, rodents, primates) coming to the fore.
>Eocene Epoch (55-34 million years ago
Early mammals proliferated in the greenhouse atmosphere at the beginning of the Eocene, but 43 million years ago, earth cooled down, and lush tropical jungles gave way to open plains and forests. 36 million years ago, earth had cooled to the extent of another Ice Age, and one again extinction occurs – a fifth of all species on earth.
>Ogliocene Epoch (34-24 million years ago)
In the cooler, dryer climate, mammals proliferate and grow gigantic – the indrichotherium grey as big as a dinosaur. In their isolated continents, South America and Australia went the way of the Marsupial. Plant life began to change, with grasses predominating.
>Miocene Epoch (24-5 million years ago)
Once again the climate becomes pleasant, with wet and dry seasons, and grasslands to feed the growing mammalian herbivores. These animals have to evole new teeth and digestive systems to become roving herds of grazing animals. Dogs and cats arise as predators, and the earth undergoes some major changes as well, such as the formation of the Himalayas, which affects weather patterns.
>Pliocene Epoch ( 5-1.8 million years ago)
The earth is sorting itself out into different climatic regions, but North and South America collide, causing an interchange of animal species.
>Pleistocene Epoch (1.8-10,000 years ago)
The earth cools off and another Ice Age forms, leading to alternating hot and cold weather patterns. The cold lasts about 40,000 years, with the ice sheets reaching Europe, with warmer periods in between. Thick fur is the evolutionary order of the day, with animals like the woolly mammoth and woolly rhino making an appearance. In the late pleistocene, Neanderthals covered Eurasia but dies out about 30,000 years ago. This species of human co-existed with Homo Sapiens for a while, and then was replaced by the latter group. About 10,000 years ago, at the end of the last Ice Age, Homo Sapiens began farming.
>Holocene Period (10,000 years ago-present day)
Our current epoch is the holocene, which has seen the rise of humankind to become the dominant animal on earth. Like previous dominant species, we are growing enormous, but not in individual bulk – rather in numbers and impact on the earth. Paleontologists say we are living through another extinction event.
As Man proliferates, builds and alters the environment, we may be just another animal facing extinction. Life is like a work in progress that keeps getting rubbed out – but it is never snuffed out. It rises again from the ashes of extinction like a blazing fire that won’t quit – a phoenix constantly reborn – the creative fire is life itself.