The Sixth Extinction: An Unnatural History

We are the problem - humans - the cause of the sixth extinction - the sixth mass extinction that is.

Throughout the history of the earth there have been five mass extinctions, separated by very long uneventful stretches with very occasionally revolution on the surface of the earth. These are:
The end-Ordovician extinction -Intense glacial and interglacial periods created large sea-level swings and moved shorelines dramatically. The tectonic uplift of the Appalachian mountains created lots of weathering, sequestration of CO2, and with it, changes in climate and ocean chemistry.
The late-Devonian extinction - caused by rapid growth and diversification of land plants generated rapid and severe global cooling.
The end-Permian extinction - caused by intense volcanic activity in Siberia. Resulting in global warming; elevated CO2 and sulfur (H2S) levels from volcanoes caused ocean acidification, acid rain, and other changes in ocean and land chemistry.
The end-Triassic extinction - caused by underwater volcanic activity in the Central Atlantic Magmatic Province (CAMP) caused global warming and a dramatic change in the chemical composition of the oceans.
The end-Cretaceous extinction - caused by asteroid impact in Yucatán, Mexico. This caused a global cataclysm and rapid cooling.

The current extinction has its own novel cause: not an asteroid or a massive volcanic eruption, but “one weedy species.”

Atelopus zeteki

Mammut americanum

Pinguinus impennis

Discoscaphites jerseyensis

Dicranograptus ziczac

Patella caerulea

Acropora millepora

Alzatea verticallata

Eciton burchellii

Myotis lucifugus

Dicerorhinus sumatrensis

Homo neanderthalensis

Homo sapiens

Right now, in the amazing moment that to us counts as the present, we are deciding, without quite meaning to, which evolutionary pathways will remain open and which will forever be closed. No other creature has ever managed this, and it will, unfortunately, be our most enduring legacy. The Sixth Extinction will continue to determine the course of life long after everything people have written and painted and built has been ground into dust...”