Saturday, 8 March 2014

Chapter 13: 'Simplest Possible Life?'

The following elaborates on a post made by the Amazon user 'stickler', which you can see here.

Chapter 13 of The Greatest Hoax on Earth addresses the origins of life on Earth.  On pages 224-8 Sarfati discusses the complexity of cells and contends that cells have always been too complex to have evolved from any non-cellular structure.  At the end of page 227 he quotes from a New Scientist article (which discusses research into the origins of life) to support his argument:
There is no doubt that the common ancestor possessed DNA, RNA and proteins, a universal genetic code, ribosomes (the protein-building factories), ATP and a proton-powered enzyme for making ATP. The detailed mechanisms for reading off DNA and converting genes into proteins were also in place. In short, then, the last common ancestor of all life looks pretty much like a modern cell.[footnote 1]
Anyone reading the quote in isolation would conclude it supports Sarfati's argument.  But what they would not realise is that Sarfati has quoted the New Scientist article rather selectively.  The article's next sentence, omitted by Sarfati, changes the meaning:
Yet the differences are startling. In particular, the detailed mechanics of DNA replication would have been quite different. It looks as if DNA replication evolved independently in bacteria and archaea, according to Eugene Koonin at the National Center for Biotechnology Information in Bethesda, Maryland.
The article goes on to point out:
"At face value, the defining boundaries of cells evolved independently in bacteria and archaea"...If Martin is right, the last common ancestor of life on Earth was a sophisticated entity in terms of its genes and proteins, and was powered by proton currents rather than fermentation. Yet at the same time, its bounding membranes were apparently different to anything found today. It was life, but not as we know it.
The article then describes 'white smokers' – alkaline hydrothermal vents, an important area of origins of life research (mentioned only in passing by Dawkins in The Greatest Show on Earth, and not addressed by Sarfati).[2]  After outlining how these vents make an ideal setting for the "RNA world hypothesis (which is discussed by Sarfati on pages 234-46), the article concludes:
The last common ancestor of all life was not a free-living cell at all, but a porous rock riddled with bubbly iron-sulphur membranes that catalysed primordial biochemical reactions. Powered by hydrogen and proton gradients, this natural flow reactor filled up with organic chemicals, giving rise to proto-life that eventually broke out as the first living cells - not once but twice, giving rise to the bacteria and the archaea.
The way Sarfati has quoted the New Scientist article gives the impression the last common ancestor was basically as complex as a modern cell, whereas the article actually states the last common ancestor was not even a free-living cell.  Given Sarfati's creative use of non-creationist sources elsewhere in The Greatest Hoax on Earth (see for example pages 57, 106, and 156-7), it is likely he has deliberately used the New Scientist quote out of context.

Part of the problem is that Sarfati seems to have conflated the ideas of a 'simple cell' and of 'simple life'.  But the simplest possible life does not necessarily have to be a cell.  Another complicating factor is that the last common ancestor does not necessarily have to be the simplest possible life, as it may not have been the first living thing.  This is best explained by physicist Paul Davies (whom Sarfati quotes in support of a different point on page 226):
It is important to realise that the last common ancestor of life on Earth is not necessarily the same as the first living thing.  To understand this, it is helpful to use Darwin's metaphor of the tree of life, in which, from a simple originating "trunk," new species have arisen by branching and re-branching over time.  Extant life is represented by the twiglets at the top of the tree.  By tracing back from two extant organisms, their last common ancestor will be encountered at the point where the branches meet.  Taking all life on Earth today, we can imagine following the myriad branches right back to a deep common branching point – the universal ancestor organism.  But this branching point may not lie on the central trunk of the tree.  There may have existed earlier branches of the tree of life that became dead ends, i.e. have no surviving descendants today.
Indeed, from the foregoing it will be clear that the universal ancestor must have already been an immensely complicated and sophisticated organism.  There was surely a long period of prior evolution leading up to it.  Pushing the tree analogy to the extreme, we can identify the origin of life with the single stem (or trunk, or root) from which all the subsequent branches sprang.  Taking this literally implies that all life would have descended from a single microbial Adam.  However, this interpretation is over-simplistic.  Microbiologists know that genes can be transferred laterally between organisms, and this can blur the unique association of species with tree branches.  In the ancient, primitive microbial realm, about which almost nothing is known, the tidy compartmentalisation into different competing species may have broken down.  All we can really say with confidence is that all life on Earth has descended from a community of genetically promiscuous closely inter-related microbes.


References: 

[1] Nick Lane, 'Was our oldest ancestor a proton-powered rock?', New Scientist, Issue 2730 (19 October 2009) http://www.newscientist.com/article/mg20427306.200-was-our-oldest-ancestor-a-protonpowered-rock.html; available in full online at: http://www.sott.net/articles/show/195226-Was-our-oldest-ancestor-a-proton-powered-rock

[2] A summary of the hydrothermal vent theory accompanied the New Scientist article cited above.  It is available in full online.  See: Nick Lane and Michael Le Page, 'How life evolved: 10 steps to the first cells', New Scientist, Issue 2730 (2009) http://www.newscientist.com/article/dn17987-how-life-evolved-10-steps-to-the-first-cells.html

[3] Paul Davies, 'The origin of life I: When and where did it begin?', Science Progress, Vol 8, No 1 (2001) http://cosmos.asu.edu/publications/papers/OriginsOfLife_I.pdf

4 comments:

  1. Just wanted to say- really like the blog and it's even handed and thorough approach. Don't stop blogging anytime soon!

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  2. I have mentioned the blog's existence to Dr Sarfati ...
    https://www.facebook.com/permalink.php?story_fbid=738276582850512&id=223583015475&comment_id=7859552&offset=0&total_comments=73
    Ashley H-R
    PS In case of any doubt, I am not Stickler.

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    Replies
    1. I suspect Sarfati would view my efforts in much the same way Dawkins would view Sarfati's book (if he were ever made aware of its existence)...

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