34 Self and the Phenomenon of Life
b2726 Self and the Phenomenon of Life: A Biologist Examines Life from Molecules to Humanity “9x6”The biochemical uniformity poses some perplexing questions. Did
life occur only once on Earth from a single organism or from a closely
related interbreeding population (a unique, contingent event)? Or did it
happen multiple times as a result of thermodynamic imperative?
3.5 The Question of Life’s Origin
The Earth is estimated to be 4.6 billion years old, and there is abundant
fossil evidence that life existed 3.8 billion years ago.^11 Since at the start
the Earth was in a chaotic state hostile to life, being constantly bom-
barded by meteorites, comets and other objects, a reasonable guess is
that the first life appeared between 4.2 and 3.8 billion years ago.
The origin of life is a unique historical event that cannot be faith-
fully reenacted. The best we can do is to obtain observable facts or
experimental clues that might help us piece together a plausible hypoth-
esis. How life started is both a chemical and organizational problem.
Although the precursors are everywhere, the problem is how they came
together to form an intricate network. The three interdependent com-
ponents outlined above had to be ready at the same time for the wheel
of life to start turning and continue in perpetuation.
Ever since the original “primordial soup” idea suggested by Darwin,^12
there has been no shortage of theories on the origin of life, among which are:
deep-sea hydrothermal vents; underground aquifers; partially frozen lakes;
comets; clay surface... In this chapter I shall deal with some of the proposed
scenarios and stress the pertinence of self to the issue of life’s origin.
3.6 Ingredients of Life are Everywhere in the Universe
Simple organic molecules that can potentially serve as starting materials
for life have been detected in meteorites, comets, cosmic clouds, and
interstellar dust. Meteorites and comets are leftovers from the birth of
the solar system; they are molecular fossils preserved in time and there-
fore are likely to be present in the early Earth. Cosmic clouds and dust,
believed to be leftover of supernova explosions, are cradles of new galax-
ies and stars, including our sun.