Geology Reference
In-Depth Information
porating novelty and undergoing Darwinian evolution.” What is perhaps most remarkable
about this development is that Jerry Joyce, realizing the subtlety of life, modestly amended
NASA'sdefinitionratherthanstakingaclaimtothehistoric,ifFrankensteinian,distinction
of being the first to create life in the lab.
Raw Materials
How did nonliving planet Earth invent the intertwined traits of metabolism and genetics?
Most of us in the origins-of-life business suspect that the emergence of the first cell was
an inevitable geochemical process. Earth possessed all the essential raw materials. Oceans,
atmosphere, rocks, and minerals were rich in the necessary elements: carbon, oxygen, hy-
drogen, nitrogen, sulfur, and phosphorus. Energy, too, was abundant: solar radiation and
Earth's inner heat provided the most reliable sources, but lightning, radioactivity, meteor
impacts, and many other forms of energy might have contributed. (And there are, conse-
quently, at least as many theories of life's origins as there are sources of elements and en-
ergy.)
On one point just about everyone agrees: carbon, the most versatile element of the peri-
odic table, played the starring role. No other element has such rich molecular designs or
such diverse molecular functions. Carbon atoms possess an unmatched ability to bond to
other carbon atoms as well as to myriad other elements—notably hydrogen, oxygen, ni-
trogen, and sulfur—with up to four bonds at once. Carbon can form long chains of atoms,
or interlocked rings, or complex branching arrangements, or almost any other imaginable
shape. It thus forms the backbone of proteins and carbohydrates, of fats and oils, of DNA
andRNA.Onlyversatile carbon-based molecules appeartosharethetwindefiningcharac-
teristics of life: the ability to replicate and the ability to evolve.
Every morsel of food we eat, every medication we take, every structure of our bodies
and the bodies of every other living thing, is loaded with carbon. Carbon-based chemicals
are everywhere: in paints, glues, dyes, and plastics, in the fibers of your clothes and the
soles of your shoes, in the pages and binding and ink of this topic, and in energy-rich fuels
from coal and oil to natural gas and gasoline. And, as we'll see in Chapter 11 , our grow-
ing reliance on carbon-based fuels and other chemicals is implicated in troubling shifts in
Earth'snear-surfaceenvironment—changesthatareoccurringatapaceperhapsunmatched
in millions of years.
Still, carbon cannot have undergone the remarkable progression from geochemistry to
biochemistry by itself. All of Earth's great transformative powers—water, heat, lightning,
and the chemical energy of rocks—were brought to bear in life's genesis.
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