Please turn on javascript in your browser to play chess.
Science Forum

Science Forum

  1. 01 Oct '14 21:54 / 6 edits
    Here is yet another theory on that:
    http://phys.org/news/2014-10-handedness-life.html

    unfortunately, it seems to me obviously flawed and for the same reason why every other theory I have ever heard about on this is obviously flawed: it assumes that the very first life must have had molecules with handiness even through there is good reason to think this unlikely. It says:
    “....understand where and when the handedness of life's molecules originated is to know the origin of life.
    ...” which I think must be false.
    All simulations of the early Earth show organic molecules formed with little or no bias for having more left-handed over right-handed molecules or vice versa. Therefore, the most obvious conclusion seems to me that can be reached is that the first life that formed probably didn't have any special preference for molecules with the same handiness. If the first protocell was fussy about the handiness of the molecules in its environment then I would guess it would have been unlikely to survive long. So I think the first protocell was probably insensitive to molecular handiness and just used whatever molecules was available regardless of their handiness.

    It seems pretty obvious to me that the bias of handiness of life's molecules probably came sometime after the first life formed and when life started synthesizing its own organic molecules rather than just taking and relying on those that spontaneously formed in its environment, Modern day organic molecules such as amino acids and sugars are mainly produced by enzymes in plants and each synthesizing enzymes nearly always produces organic molecules of all the same handiness.

    I believe the most plausible explanation the reason for the handiness bias that developed was by pure chance mutations: whatever bias first developed by pure chance was the one that life stuck to for then on because, once a life form produces, say, all of its own amino acids, it quickly evolves to depend on whatever handiness just happened to be the handiness of those amino acids that the first enzymes produced. Once that happens, there is no going back because any mutation that produces amino acids of the opposite handiness will produce amino acids that not only would that life not need but would probably interfere with its biochemistry now evolved to depend on the original handiness of the amino acids in many different ways thus natural selection will weed out those mutations.
    If this explanation is correct, there was exactly just as much chance that life could have evolved to have all the exact opposite handiness of its molecules and mere pure chance, and no mysterious force, made them evolve one type of handiness over the other.
  2. Standard member sonhouse
    Fast and Curious
    02 Oct '14 12:14
    Originally posted by humy
    Here is yet another theory on that:
    http://phys.org/news/2014-10-handedness-life.html

    unfortunately, it seems to me obviously flawed and for the same reason why every other theory I have ever heard about on this is obviously flawed: it assumes that the very first life must have had molecules with handiness even through there is good reason to think this unl ...[text shortened]... ere pure chance, and no mysterious force, made them evolve one type of handiness over the other.
    News at 11

    It will take finding extra terrestrial life forms to figure that one out. If we find life under the surface of Europa and it is opposite ours then we have something to tag a new hypothesis on, till then, it's still hypothesis.