Life uses only left-handed amino acids (Talk.Origins)
The twenty amino acids used by life are all the left-handed variety. This is very unlikely to have occurred by chance.
- Watchtower Bible and Tract Society. 1985. Life--How Did It Get Here? Brooklyn, NY, pg. 43
It is agreed that this claim is not valid[Reference needed], but interestingly Talk Origins missed the real reason. The simple fact is that the amino acids used by life are manufactured by a cell’s machinery. Given this, it is likely that a cell’s machinery would produce only left or right handed amino acids and not both. Cars are made with both right and left side driver positions, but each assembly line only makes one type. As such, it is logical from both Evolution and Creation perspectives that the amino acids used by life should be all right or left handed (see chirality). Since the odds of getting one or the other is 50/50 the fact that all amino acids used by life are left-handed is not beyond chance.
That said, one of their responses still deserves comment:
(Talk.Origins quotes in blue)
2. Amino acids found in meteorites from space, which must have formed abiotically, also show significantly more of the left-handed variety, perhaps from circularly polarized UV light in the early solar system. The weak nuclear force, responsible for beta decay, produces only electrons with left-handed spin, and chemicals exposed to these electrons are far more likely to form left-handed crystals. Such mechanisms might also have been responsible for the prevalence of left-handed amino acids on earth.
Another possible explanation would be that the meteors in question originated on the Earth, and thus the amino acids did form biologically.