Extra Ordinary Animals

Th e earth, from a purely celestial point of view, is unremarkable. It is a small planet in a solar
system orbiting a medium-sized star in a smallish galaxy, the Milky Way, which contains billions
of solar systems. Th e Milky Way is but one of billions upon billions of galaxies in the incomprehensible
vastness of the universe. Yet, in one respect, the earth is special beyond compare. It is the
only place we know of on which there is life.
Life is such a small, seemingly insignifi cant word, yet it encompasses a fantastic diversity of
living forms. Th e exact time and nature of life’s appearance on the earth has divided scientists for
decades, and it will continue to do so because the time spans with which we are dealing are huge,
almost impossible for us to grasp, and the evidence is fragmentary and hard to come by.
What we do know is that the earth is very, very old—4.6 billion years old to be exact—but
for the vast majority of this time, it was a lifeless globe cooling from the fi res of its creation,
circling the sun in the young solar system, while being heavily bombarded by asteroids. Over
hundreds of millions of years, the earth changed and the asteroid impacts became less frequent.
Oceans formed and our planet became slightly more hospitable, but conditions on this primordial
Earth were still very diff erent from the comparatively balmy conditions we enjoy today. And
then, more than 3 billion years ago, the fi rst life evolved. Where and how are questions we can
only make good educated guesses at, but an experiment conducted in the 1950s by scientists in
the United States showed that lightning bolts discharged through an atmosphere, the likes of
which could have shrouded the young Earth, could have produced biological molecules—the
precursors of the fi rst simple cells. Although these experiments have since been called into question,
as more recent fi ndings suggest that the mix of gases used by the scientists to mimic the
atmosphere of the young earth was probably inaccurate, they do give us an idea of what may
have happened all those millions of years ago. Th e complexity of these fi rst biological molecules
increased over the eons, eventually forming the fi rst self-contained biological systems, which in
turn gave rise to the fi rst proper cells—the fi rst life.

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