Geology Reference
In-Depth Information
Most other bio-building blocks don't self-organize, but they can become concentrated
and arrayed on the safe, protective surfaces of rocks and minerals in what's known as
template-directed synthesis, the second of the two selection processes. Our experiments,
conducted at the Carnegie Institution over the past decade, reveal that many of life's most
vital molecular building blocks stick to virtually any natural mineral surface. Amino acids,
sugars, and the components of DNA and RNA adsorb onto all of Earth's most common
rock-forming minerals in basalt and granite: feldspar, pyroxene, quartz, and others. What's
more, when several molecules compete for the same piece of crystal real estate, they often
cooperate and yield complex surface structures of their own that may promote even more
adsorption and more organization. We concluded that wherever the prebiotic ocean con-
tacted minerals, highly concentrated arrangements of life's molecules are likely to have
emerged from the formless broth.
Here I should issue a caveat. In origins-of-life research (and probably in most other dis-
ciplines as well), scientists gravitate to models that highlight their personal scientific spe-
cialty. Organic chemist Stanley Miller and his cohorts saw life's origins as essentially a
problem in organic chemistry. Geochemists, by contrast, have tended to focus on more in-
tricate origins scenarios involving such variables as temperature and pressure and chem-
ically complex rocks. Experts in membrane-forming lipid molecules promote the “lipid
world,” while molecular biologists who study DNA and RNA view the “RNA world” as
the model to beat. Specialists who study viruses, or metabolism, or clays, or the deep bio-
sphere have their idiosyncratic prejudices as well. We all do it; we all focus on what we
know best, and we see the world through that lens.
I'm trained in mineralogy, so you can easily guess where my origins preferences lie.
Meaculpa.Manyotheroriginsresearchershavealsosettledonsuchaconclusion—indeed,
more than a few prominent biologists have also gravitated to minerals, because origins-of-
life scenarios that involve only oceans and atmosphere face insurmountable problems in
accounting for efficient mechanisms of molecular selection and concentration. Solid min-
erals have an unmatched potential to select, concentrate, and organize molecules. So min-
erals must have played a central role in life's origins.
Right and Left
Biochemistryiscomplex,withinterwovencyclesandnetworksofmolecularreactions.For
these intricately layered processes to work, molecules have to have just the right sizes and
shapes. Molecular selection is the task of finding the best molecule for each biochemical
job, and template-directed selection on mineral surfaces is now the leading candidate for
how nature did it.
