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elliot svensson
elliot svensson
4:01 PM
@DavidHammen, would you agree, with the Smithsonian teaching resource "Good Thinking!" / "Time: It's So Deep", that the first bacteria popped up 3.5 billion years ago?
 
elliot svensson
elliot svensson
4:40 PM
Some note-taking: isochrons have resulted in self-incompatible measurements in the past, notably the Chibougamou greenstone belt of Quebec, where we saw a Rb-Sr isochron of 2290 +- 170 m.y., which is "cut by a tonalite pluton" with a Rb-Sr isochron age of 2520 +- 160 m.y.
 
DevSolar
DevSolar
@elliotsvensson: You toss out all the arguments, evidence and references that are put forward to explain the subject matter to you, and go back to a strangely defensive "come on, claim what I consider to be wrong!" position.

You haven't asked me, but that 3.5 billion year number is *scientific consensus at this point of time*. Even those who disagree with that number do not doubt the "Great Oxygenation Event" which, at 2.8-2.4 billion years ago, marked the appearance of *free* oxygen in the atmosphere. There is no doubt that photosynthesis appeared "long" before that (e.g. http://adsabs.ha…
 
elliot svensson
elliot svensson
Elliot Lake in Canada! I'm Canadian!
Must be named for Pierre Elliot Trudeau.
@DevSolar, if what I consider to be wrong isn't wrong, then it wouldn't be hard for somebody to repeat what's called "a fact" by the teaching resources I am quoting and assert it here.
@DevSolar, I don't think it's inappropriate to reset the discussion to the original point: is skepticism warranted regarding the claim that photosynthesis appeared 3.5 billion years ago?
More note-taking: isochrons at Elliot Lake were problematic (see journals.lib.unb.ca/index.php/GC/article/viewFile/2828/3346 - referencing "Goldich 1972 Fallacious Isochrons and Wrong Numbers" ) although the uncertainty was supposed to be toward falsely-young reporting.
 
DevSolar
DevSolar
5:05 PM
"Is skepticism warranted regarding the claim that photosynthesis appeared 3.5 billion years ago?"

Not with regards to what Skeptics.SE considers to be skepticism, no.
 
elliot svensson
elliot svensson
@DevSolar, will you be so kind as to be more specific about that?
 
 
2 hours later…
DevSolar
DevSolar
6:50 PM
I could but there would be nothing "kind" about it. You have been given plenty of information about why that 3.5 billion years is neither biased, fake, or misleading. That's what Skeptics.SE is about, and for. But you are continuing a discussion, intend on convincing others of your non-consensus opinions, and that is NOT what Skeptics.SE is about.
Move along, there is nothing left to be said here.
 
elliot svensson
elliot svensson
7:09 PM
@DevSolar, would you agree with the Smithsonian that photosynthesis popped up 3.5 billion years ago?
 
elliot svensson
elliot svensson
7:53 PM
@DevSolar, the most prominent researcher on the 3.5 billion year dates, Abigail Allwood, in 2007 acknowledged that "In fact, Moorbath (2005) pointed out that there is ‘no consensus’ among scientists for life's existence prior to 1.9 Ga (e.g. compare Brasier et al., 2002, Brasier et al., 2005, Brasier et al., 2006 with Schopf, 2006)." (1/2)
"The lack of consensus centres on challenges that exist largely because key outcrops are typically structurally deformed, chemically altered and have limited lateral continuity." sciencedirect.com/science/article/pii/S0301926807001234 (2/2)
And following Allwood's 2007 paper, we read in 2009 that " the biogeneicity of the famous stromatolites (or stromatoloids) of the 3.5 Ga old Strelley Pool chert in Australia has been controversially debated (e.g., Lowe, 1994, Buick et al., 1981, Grotzinger and Knoll, 1999, Brasier et al., 2006, Allwood et al., 2007)." sciencedirect.com/science/article/pii/S0012825208000883
 

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