Left-Handed Amino Acid Puzzle Remains
A new suggestion of how life ended up with left-handed amino acids comes up short.
A NASA Goddard press release reported that amino acids found in the Tagish Lake meteorite (British Columbia, 2000) showed some preference for left-handed aspartic acid, but less excess for alanine. As usual, the science news media (e.g., Astrobiology Magazine, Science Daily, PhysOrg) and blogs (e.g., Darwiniana) all echoed the press release uncritically, graphics and all, so Creation-Evolution Headlines will have to do the job they should have done: evaluate the significance of the claim and see whether it solves the long-standing homochirality problem in biology (for background, see here and here).
Here are problems admitted by the press release:
- Only 2 of the 20 amino acids used by life were mentioned.
- The excess of one hand was 4x for aspartic acid, but only 8% for alanine.
- The scientists do not know what process created the excess, but it was not polarized light, because it must have occurred inside the meteorite. “Perhaps” it was due to properties of crystallization.
- The meteorite amino acids were enriched in carbon-13, not the carbon-12 common in life.
- An astrobiologist admitted, ” “Synthetic proteins created using a mix of left- and right-handed amino acids just don’t work.”
- Left-handed amino acids and right-handed sugars were noted as “a prerequisite for life.”
- All ordinary methods of synthetically creating amino acids result in equal mixtures of left- and right-handed amino acids.
- The finding complicates searches for extraterrestrial life, because it means finding one-handed molecules may not be a biomarker.
Here are more problems not mentioned in the press release:
- Life requires 100% purity of one hand.
- A mere “excess” is not enough; one wrong-handed amino acid ruins the protein chain.
- The astrobiologists still have no theory for how the meteorite enriched one hand in the aspartic acid.
- The astrobiologists still have no theory for how a prebiotic “cell” ended up with 100% pure amino acids.
- Their “snowball” analogy for how crystals might amplify the excess is worthless, because cells had to incorporate amino acids in solution, not as crystals.
- The article used wishful-thinking words like perhaps, could, and might a dozen times.
- The article said further experimentation is needed.
In summary, since the press release proposes no physical theory for the excess, and no testable hypothesis for how the excess originated, could have been sustained, or could have been incorporated into life, the press release adds little more than anecdote to the puzzle of one-handedness, and nothing in the way of understanding.
Same old story; irrelevant mumblings we’ve been reporting for over a decade (e.g., 2/17/2001, 5/09/2012; search on “homochirality” for more) . Come back when you have a materialist explanation, not a just-so story. Intelligent design explains the observations. Face up to the physics, don’t twist them to your worldview, Darwinists.