Earths five Major Extinctions

“The question now at issue, whether the living species are connected with the extinct by a common bond of descent, will best be cleared up by devoting ourselves to the study of the actual state of the living world, and to those monuments of the past in which the relics of the animate creation of former ages are best preserved and least mutilated by the hand of time.” (ref:  Sir Charles Lyell, The Antiquity of Man (1863), 470.)

With that said, there have been five major extinctions throughout creation.  The reasons are not always clear on why something or someone becomes extinct, so there are many speculations regarding the destructions that have occurred.  It may be hard to believe but the five mass extinctions were more devastating than the extinction of the dinosaurs.

The first such extinction occurred in the Ordovician-Silurian Period.  Although the first, this event turned out to be the third largest in history. Nearly 440 million years ago it was the sea creatures that ruled the globe with those species on the land coming in second.  This mass extinction took place in two waves.  In the first wave of extinction most of the life in the sea that included trilobites and brachiopods among others lost their lives. Afterwards there was a period of several centuries which encapsulated the transgressions and regressions of glacial movements and the rise and fall of mountain ranges in North America occurred such as the Appalachians.  Records have indicated that over 85% of all species were eventually lost by the time the second wave was completed.

Around 365 million years ago the second great mass distinction took place.  Within the latter part of the Devonian Period 35% of genera lost their lives which included nearly three quarters of the species of the planet. There was global cooling followed by planetary warming which produced drawdown of carbon dioxide on the planetary level as well.  Evidence shows there were inordinate amounts of oxygen, or lack thereof, within the species living at the time thereby showing that the cooling and warming may have caused the extinction.

The largest of the five greatest mass extinctions is the third.  At the tail of the Permian Era that existed 245 million years before the current era volcanoes in the Siberian region erupted, and erupted and erupted.  Hydrogen sulfide and carbon dioxide were released into the atmosphere and spread globally.  The oceans became acidic.  Nearly 60% of the genera were destroyed and almost 100% of the species went into extinction.

The Triassic and Cretaceous eras housed the last two mass extinctions.  The Triassic event saw the increase of rainfall, and yet another rise of CO2 levels in the atmosphere across the planet.  This was followed by the rise of temperatures on a grand scale and calcification problems in the seas.  Almost half of the genera died and 80% of all species became extinct. 

Most people are aware of the Cretaceous event that took place.  At the very beginning of the era and at the transition from the Tertiary period, an event occurred that wiped out half the life on the planet.  This was the age of the dinosaur.  Evidence of a giant meteor impact was found in the Yucatan is thought to be the cause of the fifth mass distinction.  Other factors are also thought to be involved.  Volcanism, global warming, the natural decline of some of the organisms of the time, and tectonic shifts, combined with the meteor explosion, are thought to be blamed.

In The Antiquity of Man Sir Charles Lyell proposes that perhaps the living species of today’s world are interconnected with those extinct species of the past.  He thought if time was spent in studying the “actual state of the living world” while looking into the “monuments” left behind by the extinct races that perhaps scientists will understand what happened just a little bit better.  The five greatest mass extinctions saw global climatic changes, impacts that could shift the Earth in its orbit and geological shifts of the Earth itself.  Perhaps, as Sir Lyell thought, people really can learn a bit so as not to repeat the offense nor to have the past left in the past, but rather have it help the future of the planet.