Life’s Origins 155liquid water to condense and form oceans much before 4.0 billion years ago, but tiny zircon
grains from Australia were recently discovered that seem to have a distinctive chemistry
indicating oceans as early as 4.3–4.4 billion years ago (Wilde et al. 2001; Valley et al. 2002).
If so, then the earth’s surface cooled down to below 100°C (the boiling point of water) in only
250,000 years after its formation 4.65 billion years ago. There is nearly a billion years of time
between when the first oceans form and the first clear fossils are known, plenty of time for
life to evolve (more than once, if necessary), given these constraints.
Because these earliest fossils are tiny carbonized films preserved in cherts and flints,
they provide little evidence for the chemical processes that formed life. All the organic
chemicals in them have long been transformed by heat and pressure into other carbon
compounds (usually pure carbon in the form of graphite, the “lead” in your pencil). We
have only their shapes (fig. 6.2) to demonstrate that they were once living things. For
earlier stages in this process, we cannot use the fossil record. Instead, we must try an
experimental approach, using the constraints imposed by our knowledge of earth’s his-
tory and the nature of organic chemistry to find possible solutions. Naturally, some people
(especially creationists) label this as “guesswork” and refuse to accept any of the experi-
mental evidence to understanding life’s origins. They prefer to just say “God did it” and
stop there. They are welcome to their opinions, of course, but as we explained in chapter 1,
no true scientist falls back on this “god of the gaps” approach. The supernatural hypothesis
is simply untestable and leads nowhere. Scientists may not have all the answers to this
very complex and difficult problem, but they are not sitting on their hands or surrendering
to the unscientific supernatural approach. They are constantly trying new experimental
approaches and (as we shall soon see) have made a huge amount of progress—much more
than creationists realize.
(F)
FIGURE 6.2. (Continued )