INSIGHTS into CHEMICAL EVOLUTION and BIOLOGY
Muchof our biology has it roots in chemical evolution. It is perhaps most significant because of our placement in the habitable zone.Had our existence taken hold in a binary star system—we might be completely unrecognizable to our own selves. I, for the most part, cannot begin to speculate as to how different our species would appear and function if we had taken hold in a binary star system. Perhaps one might ask: if there were two Suns in the sky, would our species have been “under-ground dwellers” or would a different set of senses prevailed over “eyesight?” The possible permutations might be viewed as endless. Thus, the habitable zone and chemical evolution might be viewed as two synergistic aspects that have played a major role in our species’ evolution. So, what is it about chemical evolution that makes biological evolution inevitable upon the Earth?
I will attempt to illustrate how the concept of a “shadow biosphere” could illuminate our own evolution. As some may know, the “shadow biosphere” concept was introduced as a possibility when the question of “arsenic-based life” was posed approximately 3½ years ago. Although, the concept has been ruled out as a possibility for the arsenic-based life at Mono Lake (CA)–it is an intriguing concept because it offers a route for different types of biochemistry to co-exist with the current DNA/RNA models of Earth-based life.
First of all, lets attempt to understand the work covering arsenic-based life:
an extreme-bacteria was isolated from the hyper-saline/alkaline water of Mono Lake
the bacteria was “given arsenic and phosphorus” so to determine if one would be favored over the other in various “test-tube studies”
arsenic, it was reasoned, could be a plausible choice because it was one of the many other co-existing species where the bacterium was found
it was determined that arsenic and phosphorus seemed to be equally favored under conditions of their experimentation
At this point, one may argue that the finding sounds interesting and readable—but probably needs much more elaboration. However, this is where the study ended—as it was published in the journal Science. The finding came across(to the public) as revolutionary. However, as it turned out, many in the biological community panned the article and attempted to reproduce it (if not refute it). Within the next two years, the finding could not be reproduced, and the study was cited as being “poorly” done. However, the suite of articles leading up to the Science article prove to be an interesting study in how an alternative “biology “ may exist.
A partial list of the titles is as follows:
Arsenic in the Evolution of Earth and Extraterrestrial Ecosystems (2009)
Did nature also choose arsenic? (2009)
Signatures of a Shadow Biosphere (2009)
The titles are well-referenced and in appeared respected journals. However, I seem to notice a possible pattern of a logical fallacy. To me, it is as if they were anticipating a “positive outcome” from their experimentation at Mono Lake. I don’t believe “foretelling the future” was ever apart of the tool-kit of practicing scientists.
As the titles imply, the experimenters may have fooled themselves into believing that they had ultimately found a “shadow biosphere” on the Earth. The article in Science appeared as an “Express” –online article in late 2010 and final version appeared in June 2011.
Despite the “efforts” by the group of scientists—hindsight (unfortunately or fortunately) has proved to be “20-20.” An article published in Skeptic Magazine (2011) offered an interesting take on the matter, the article’s title was: “How did Life begin?” In the article author, Paul F. Deisler, Jr gives an insightful take on how chemical-evolution may be illustrated in a test-tube. His illustration was taken from the venerable evolutionary biologist, Richard Dawkins—and his book (published 6 years prior to the arsenic-based life article), The Ancestor’s Tale. Deisler recounts an experiment entitled: Spiegelman’s Monster—Sol Spiegelman took a “long” strand of RNA (that was biologically active to E. Coli) and managed to produce smaller and smaller strands of the original (3600 units into 218 units) sequentially. So, as each strand became smaller—the smaller strand was less active to E. Coli. than the previous strand–until the final (218 unit) strand was inactive with E. Coli.. So, in a nutshell, Spiegelman managed to illustrate an “evolutionary” process within 74 test-tubes. Quite possibly the astrobiologists, in their over-zealousness to find the arsenic-based specimens created a monster of their own?
Some lessons that could be taken to heart—in this case—despite the insights of possible arsenic-based life; is that experimenters may have published too hastily. Furthermore, the experimenter, through his/her own hand can hasten false results. Had each step of their analysis been re-performed and “cross-checked” their work might not have implied “arsenic-based life,” let alone “alien-type” life found at Mono Lake. Perhaps their lead articles (mentioned above) could have served a better purpose?
Partial List of References:
Davies, etal, Signatures of a Shadow Biosphere, Astrobiology, 2009.
Richard Dawkins, The Ancestor’s Tale. 2004.
Paul F. Deisler Jr., How did Life Begin? Skeptic Magazine, 2011.
Oremland, etal, Arsenic in the Evolution of Earth and Extraterrestrial Ecosystems, Geomicrobiology Journal, 2009.
Schoepp-Cothenet, etal, Comment on “A Bacterium That Can Grow by Using Arsenic Instead of Phosphorus, Science, 2011.
Wolfe-Simon, etal, Did Nature also Choose Arsenic?, International Journal of Astrobiology, 2009.
Wolfe-Simon, etal, A Bacterium That Can Grow by Using Arsenic Instead of Phosphorus, Science, 2011.