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| Amino Acid Chirality chirality with hands from http://www.nai.arc.nasa.gov/ A "chiral" molecule is one that is not superposable with its mirror image. Like left and right hands that have a thumb, fingers in the same order, but are mirror images and not the same, chiral molecules have the same things attached in the same order, but are mirror images and not the same. Although most amino acids can exist in both left and right handed forms, Life on Earth is made of left handed amino acids, almost exclusively. Source: Wikipedia |
One of the creationist 'gap' arguments you see pulled out of the toy box and dusted off once in a while is the so-called 'chirality' or handedness problem. The reason it's used so infrequently is probably because so few creationists have the capacity to understand what the term 'chirality' means. The 'problem' is to explain why all amino acids (and so biological proteins) and sugars are composed only of one enantiomere, 'L' in the case of amino acids and 'D' in the case of sugars.
Like so many creationist presuppositional 'gap' arguments, the answer is that the presupposed god did it. No evidence need ever be offered of the existence of this god nor any explanation of how or why it did whatever it is claimed to have done. 'Magic' and 'mystery' satisfy a creationist.
But now this creationist-satisfying gap might have closed according to a paper published in The Astrophysics Journal Letters by two STanford University physicists, Noemie Globus and Roger D. Blandford.
Taylor Kubota of Stanford News Service explains:
Before there were animals, bacteria or even DNA on Earth, self-replicating molecules were slowly evolving their way from simple matter to life beneath a constant shower of energetic particles from space.
In a new paper, a Stanford professor and a former post-doctoral scholar speculate that this interaction between ancient proto-organisms and cosmic rays may be responsible for a crucial structural preference, called chirality, in biological molecules. If their idea is correct, it suggests that all life throughout the universe could share the same chiral preference.
Magnetically polarized radiation preferentially ionized one type of ‘handedness’ leading to a slightly different mutation rate between the two mirror proto-lifeforms. Over time, right-handed molecules out-evolved their left-handed counterparts.
Image credit: Simons Foundation
Chirality, also known as handedness, is the existence of mirror-image versions of molecules. Like the left and right hand, two chiral forms of a single molecule reflect each other in shape but don’t line up if stacked. In every major biomolecule – amino acids, DNA, RNA – life only uses one form of molecular handedness. If the mirror version of a molecule is substituted for the regular version within a biological system, the system will often malfunction or stop functioning entirely. In the case of DNA, a single wrong handed sugar would disrupt the stable helical structure of the molecule.
Louis Pasteur first discovered this biological homochirality in 1848. Since then, scientists have debated whether the handedness of life was driven by random chance or some unknown deterministic influence. Pasteur hypothesized that, if life is asymmetric, then it may be due to an asymmetry in the fundamental interactions of physics that exist throughout the cosmos.
“We propose that the biological handedness we witness now on Earth is due to evolution amidst magnetically polarized radiation, where a tiny difference in the mutation rate may have promoted the evolution of DNA-based life, rather than its mirror image,” said Noémie Globus lead author of the paper and a former Koret Fellow at the Kavli Institute for Particle Astrophysics and Cosmology (KIPAC).
In their paper, published on May 20 in Astrophysical Journal Letters, the researchers detail their argument in favor of cosmic rays as the origin of homochirality. They also discuss potential experiments to test their hypothesis.
But of course, unless we know the precise conditions under which abiogenesis occurred, we don't even know if there is a chirality problem to be explained. The conditions as outlined in this perfectly plausible ten-step process for instance could have included catalysts which only or mainly included one enantiomete as their product, so chirality could have been an inevitable consequence of these early conditions.
However, like so many of creationism's gaps, real or imaginary, it looks like another one could be about to slam shut with no god found to be necessary. Surely, it must be beginning to dawn on creationists that their forlorn search for that one gap which this time science will find a god in, is never going to find one. Sorry creationists, but Science is going to continue to fill gaps in our collective knowledge with scientific explanations that don't include magic or magic entities. Tweet
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