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At worst, we'll be the first species on this planet to cause a mass extinction and decomplexification of life  (as opposed to the usual comets / radiation / super-volcanoes).
I was under the impression the first photosynthetic organisms caused a mass extinction by poisoning the planet with oxygen.

Wikipedia, the free encyclopedia: Oxygen Catastrophe

When evolving life forms developed oxyphotosynthesis about 2.7 billion years ago, molecular oxygen was produced in large quantities. The plentiful oxygen eventually caused an ecological crisis, as oxygen was toxic to the anaerobic organisms living at the time.

Great comment, by the way. The reference to the ultimate mortality of the species reminds me of Asimov's The Last Question.

We have met the enemy, and he is us — Pogo

by Migeru (migeru at eurotrib dot com) on Wed Jan 2nd, 2008 at 07:46:36 PM EST
[ Parent ]
Ah, but the oxygen catastrophe was caused by multiple species!

I thought about including it, but I tend to give up on googlepedia after 30 seconds, and I hadn't heard the term "oxygen catastrophe" before.

you are the media you consume.

by MillMan (millguy at gmail) on Wed Jan 2nd, 2008 at 07:58:02 PM EST
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The way I got to it was through googling "banded iron" on wikipedia. However, last time I tried that I had forgotten the exact name and it took me an inordinate amount of time to hit on "banded iron". The first time I just serendipitously hit the cluster of articles.

To nitpick a little, it was likely caused by a single taxon, unless photosynthesis was evolved indepedently by disparate organisms.

We have met the enemy, and he is us — Pogo

by Migeru (migeru at eurotrib dot com) on Wed Jan 2nd, 2008 at 08:11:35 PM EST
[ Parent ]
There also is the Late Devonian:
Reasons for the late Devonian extinctions are still speculative. Bolide impacts are dramatic triggers of mass extinctions. In 1969, Canadian paleontologist Digby McLaren suggested that an asteroid impact was the prime cause of this faunal turnover, supported by McGhee (1996), but no secure evidence of a specific extra-terrestrial impact has been identified in this case. Needless to say, there are some extinction spikes during the period, and the Alamo bolide impact in Nevada, United States, and Woodleigh crater in Australia are believed to be candidate trigger impacts for some of these events.

The "greening" of the continents occurred during Devonian time: by the end of the Devonian, complex branch and root systems supported trees 30 m (90 ft) tall. (Carbon locked in Devonian coal, the earliest of Earth's coal deposits, is currently being returned to the atmosphere.) But the mass extinction at the Frasnian-Famennian boundary did not affect land plants. The covering of the planet's continents with photosynthesizing land plants may have reduced carbon dioxide levels in the atmosphere. Since CO2 is a greenhouse gas, reduced levels might have helped produce a chillier climate. A cause of the extinctions may have been an episode of global cooling, following the mild climate of the Devonian period. Evidence such as glacial deposits in northern Brazil (located near the Devonian south pole) suggest widespread glaciation at the end of the Devonian, as a large continental mass covered the polar region.[3] Massive glaciation tends to lower eustatic sea-levels, which may have exacerbated the late Devonian crisis. Because glaciation appears only toward the very end of the Devonian, it is more likely to be a result, rather than a cause of the drop in global temperatures.

by nanne (zwaerdenmaecker@gmail.com) on Wed Jan 2nd, 2008 at 08:48:06 PM EST
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There was also a hypothesis that the first plants using wind-distributed pollen caused a mass extinction of land vertebrae (though this now seems out, with the first angiosperms being dated earlier and their rise seen less sudden).

*Lunatic*, n.
One whose delusions are out of fashion.
by DoDo on Fri Jan 4th, 2008 at 07:42:25 AM EST
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