Evolution Message Board - Msg: 26979643

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Politics : Evolution

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To: Solon who wrote (10114)	11/22/2010 8:01:20 PM
From: Jacques Chitte	Read Replies (1) of 69300

It survived. The deep-ocean vents are the prime suspect here but not absolutely necessary. By the first freeze (apx 2.2 Gy ago) cellular life already had been around for 1.5 billion years and probably permeated the hydro- and lithospheres. What fascinated me about the two snowball events is that they provided tremendous evolutionary impetus. After the first one, photosynthetic life appeared in quantity ... and changed the surface chemistry of the planet profoundly. The banded iron formations bear witness to this change. Ferrous iron is water-soluble, and the vast quantities in the oceans rained out as ferric iron, essentially rust - which is very insoluble. The banding comes from interleaved chert, basically diatomaceous sediment. The three ores that drive our steel industry - limestone, coal, iron ore - were all direct products of living things! The second snowball event set the stage for the jump to multicellular forms, to which the fossil suites of the Ediacara and the Burgess Shale bear witness. I find these to be captivating chapters in the history of both the mineral and biological histories of our earth.

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