Earth's Permian Period

The Permian Period followed the Carboniferous Period and lasted from around 299 to 251 million years ago. It is the last period of what is collectively known as the Paleozoic Era which began with the Cambrian and ended with the Permian.

The Permian Period marks the beginning of the fusion of all of Earth's continents into one giant supercontinent called Pangaea. This would have major consequences for life on earth. Such a large continent has a very large interior which is far from the sea. As Pangaea closed up, the Paleo-Tethys Ocean in the interior of the continent began to dry up, as sources of water feeding the body were cut off. This began the formation of a vast desert in the center of Pangaea which would grow throughout the Permian to include much of the continent. In the early Permian, the climate was much more seasonal, prone to hot summers and cold winters as opposed to the more consistently tropical climate of the Carboniferous. By the late Permian, the majority of life on earth was subjected to a burning hot climate which was also very dry. In addition to the desert conditions, Pangaea also had a very small coastline despite its large size. A series of small continents will have a larger coastline than one giant one, and this had disastrous effects on many marine ecosystems.

In the oceans, mollusks were making it big, while many species of large fish and sharks were on the decline due to the changing global conditions. Lungfish and coelacanths which are both alive today became more diverse, but other lobe-finned fishes were dying at during the Permian.

The first modern trees began to appear during the Permian Period, mainly as a result of the more arid conditions. The great swamp forests of the Carboniferous could not survive the change in climate toward a much colder and drier world. Many hardy new trees began to take the place of the giant ferns and wet-growth trees, including conifers, which were able to withstand the wild temperature fluctuation with their lack of deciduous leaves and thick bark. Ferns began to decline in importance due to the delicate nature of their reproduction, which was not suitable for more arid environments.

It is during the Permian that a very important family of land-dwelling tetrapods really began to make it big. These synapsids, also known as mammal-like reptiles, included large herbivores such as edaphosaurus and predators like dimetrodon in the early Permian. These mammal-like reptiles are closely related to true mammals and to our own ancestors. By the late Permian, mammal-like reptiles had continued to thrive even in the vast deserts of Pangaea. Their scaly skin, low need for water, and smaller food requirements due to being ectotherms allowed the reptiles to flourish when other organisms were dying out in large numbers. Amphibians were hit especially hard when the shallow waterways they once thrived in began to dry up. Since amphibians depend on water to keep their skin wet as well as lay their eggs, the Permian desert conditions were very inhospitable indeed.

The Permian Period ended with the most disastrous mass extinction event ever to strike the Earth. Between 90 and 95% of all marine and 70% of all land-dwelling species died off as a result of this catastrophic event. The aforementioned desert conditions caused by the fusion of the continents into the supercontinent of Pangaea helped to contribute to this extinction. Shallow seas were draining away, destroying entire marine ecosystems. Furthermore, evidence points to an increase in volcanic activity which further altered the climate by pumping vast amounts of toxic chemicals and greenhouse gases into the atmosphere. The toxic agents could have also depleted the ozone layer, thus exposing organisms to harmful ultraviolet rays from the sun that were normally shielded. All of these factors taken together spelled doom for the majority of life on Earth, with only the toughest and hardiest animals surviving to continue the saga of evolution on our planet.