| What is the Sixth Extinction? It is the sixth known time in the biological history of our planet that there is/has been a major die-off of species, representing a large percentage of the total multicellular species on the Earth. And it is happening NOW. The current extinction has been termed the Holocene Extinction. As with most extinction events, the die-offs are not simultaneous and instantaneous, but rather occur over a period of time. The Holocene Extinction can be construed to include the widespread extinction in the Americas of large mammals around 20,000 years ago. Many theories attribute these extinctions to human presence. The annual rate of extinctions is currently high, although most of them are smaller, non-"charismatic" species. Many larger species have disappeared: stellar sea cow, Tasmanian wolf (thylacine), Japanese river otter, Dodo, Passenger Pigeon, Carolina Parakeet, Ivory-Billed Woodpecker, and on and on (note: it is a convention that names of birds are always capitalized, but not names of other species unless a proper name is involved). Species that have become within human history takes many pages to list. One estimate is that as many as 20% of all species may disappear by 2030; another claims an extinction rate of 50% of all living species within a century. These are not wild-eyed claims, but the results of careful scientific analysis, and are assuming current conditions and trends.
Previous extinctions are listed below right: |
Major marine fossil extinctions of the past. From Wikipedia (user Smith 609)
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- Ordovician–Silurian Extinctions
- about 450 million years ago
- about 2/3 of all species disappeared
- caused by global cooling
- Late Devonian Extinction
- about 370 million years ago
- about 2/3 of all species disappeared
- causes unclear but apparently multiple
- Permian–Triassic Extinction
- about 250 million years ago
- over 90% of all species disappeared
- causes unclear but apparently multiple
- Triassic–Jurassic Extinction
- about 200 million years ago
- about 3/4 of all species disappeared
- caused apparently by climate change following asteroid impact
- Cretaceous–Paleogene Extinction
- 66 million years ago
- about 3/4 of all species disappeared
- caused by asteroid impact
- also known as K-T Event
Note: These are not all the extinction events by a long shot, just the largest ones known after the Cambrian Era - there were several huge extinctions during the Cambrian, as well, but there was little or no land life.
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