16 Self and the Phenomenon of Life
b2726 Self and the Phenomenon of Life: A Biologist Examines Life from Molecules to Humanity “9x6”the nineteenth century, people thought living things pop out of nothing,
given the right condition, such as maggots appearing from spoiled food.
The debate raged on until 1859 when Louis Pasteur settled the prob-
lem of spontaneous generation. Pasteur’s famous experiment consisted
of keeping boiled broth in a flask having an “S” shaped neck. The broth
did not get spoiled despite the free flow of room air into it. However, the
soup quickly became cloudy if the flask neck was broken or if the flask
was tilted to let the broth touch the swan-neck. (Apparently the neck
served as a trap preventing microbes entering from the outside air.) The
conclusion was clear: Life comes only from life.
Today, science tells us that more complex lives came from simpler
lives, and in this manner extrapolates to the simplest, primordial uni-
cellular life. But how did the very first life start? When in the history
of Earth did inanimate matter first turn into living matter? The clue is
chemistry. Here, a brief review of chemical concepts is necessary and
will be helpful. (For those who are not comfortable with chemistry, feel
free to skip the first two thirds of this chapter and go to the section
“What have we learned about the origin of life?”)
3.1 How Chemistry Shapes the World
Everything we come in contact with is composed of molecules, living
things not excepted. Molecules are formed from atoms by chemical bonds.
Atoms, in turn, are made up of three smaller components: protons, neu-
trons and electrons, the first two being made up of quarks (three quarks for
each proton and neutron, out of six possible choices). The varied combina-
tions of protons, neutrons and electrons produce all the elements of mat-
ter. Protons and neutrons are approximately of equal mass, but electrons
are much smaller, about 1/2000 that of a proton. However, it is the latter
that imparts distinctive chemical properties to each element. While pro-
tons and neutrons pack tightly inside the nucleus, the tiny electrons swirl
around at an incredible speed in the almost empty space surrounding the
nucleus (in quantum mechanics, electrons are visualized as clouds). The