lpetrich

According to research done by <a href="http://epsc.wustl.edu/admin/people/blank.html" target="_blank">Carrine Blank</a>, also reported in <a href="http://www.geosociety.org/news/pr/02-44.htm" target="_blank">this article</a> and <a href="http://gsa.confex.com/gsa/2002AM/finalprogram/abstract_46069.htm" target="_blank">this abstract</a>, cyanobacteria are latecomers to the world of life, being one of the last of the big groups of prokaryotes to branch off from the others.

This is not an absolutely new conclusion, however, <a href="http://www.biomedcentral.com/1471-2148/1/4" target="_blank">this genomic timescale for eukaryotic-cell evolution</a> comes to a similar conclusion.

Also, cyanobacteria are relatively sophisticated organisms, with two-step photosynthesis; other photosynthetic prokaryotes have only one-step photosynthesis, and they do not release oxygen.

But one interesting result is that sulfur-isotope fractionation started at about 2.7-2.4 billion years ago, indicating some sort of large-scale sulfur metabolism back then. By comparison, atmosphere oxygenation started at about 2.3-2.2 billion years ago.

As to what oxidized the iron to produce the massive Banded Iron Formations of the Archean, <a href="http://gsa.confex.com/gsa/2002AM/finalprogram/abstract_43056.htm" target="_blank">this paper</a> proposes an interesting culprit: photosynthetic bacteria like Chlorobium, which do not release oxygen, but instead oxidize iron from Fe++ to Fe+++. Alternatively, solar UV could split water molecules, producing a limited amount of O2 as the released H2 evaporates to outer space.

Unfortunately, the articles I found on this subject do not include any microbe family trees or precise details of the possible sulfur metabolism.

Quetzal

You may not believe this lp, but the cretinists are ALREADY touting this as another "death knell" for evolution, primarily by using the "cyanobacteria was the first lifeform" strawman. Still, it's not all that big a deal - and Blank even admits that her hypothesis is "not well supported" yet. For instance, <a href="http://www.pnas.org/cgi/content/full/98/5/2170" target="_blank">this article</a> talks about a 2.8 gya node, while Feng, et al, for instance in this article from 1997, <a href="http://www.pnas.org/cgi/content/full/94/24/13028?ijkey=WXvrs1sXmCBUw" target="_blank">Determining divergence times with a protein clock: Update and reevaluation</a> mentions 2.1 gya cyanobacteria and Gram-positive and Gram-negative eubacteria divergence, with the divergence of archaea and eubacteria between 3 and 4 billion years ago.

Why do the creationists seize on EVERY single article ever published that might provide new data to an old question as somehow "refuting" evolutionary theory? I simply cannot fathom how that mindset works.