There is a significant disagreement about where life most likely came to
be on Earth: 1) in deep sea alkaline hydrothermal vents or 2) in drier
surface areas bubbling with geysers “…bringing hot…and rich gases”
together. Hydrogen cyanide and sulfide could collect and react with the
help of UV radiation to self-replicate. Lab studies have shown that
blocks of DNA can arise this way.
The other theory–that life began in the sea–emphasizes the need for an
initial source of energy to get life started. It questions the source of
fossil cells (stromatolites) claimed to be found in 3 to 4
billion-year-old rocks in Australia. A summary article in
September/October 2017 popsci.com reports that the two differing groups
of theorists do agree on one thing–that life on Earth appeared more
quickly than previously thought–perhaps in a few million years, not
billions.
In trying to be realistic about the origins of life, both here and
anywhere, we face several dilemmas. One is the apparent fact that life
happened only once on Earth–and only three basic kinds of life
survived, to evolve or not, over the eons. In addition, we complex
organisms wouldn’t have happened if the pre-mitochondrial organisms
hadn’t indulged in symbiosis with other simple forms, like bacteria or
archaea. Those early symbionts produced enough energy to evolve
nucleated cells as building blocks for us complex critters..
Adding intrigue to possibility is the fact that the chemical building
blocks of life are found on all sorts of astronomical objects, both near
and far–comets, asteroids, planets, moons. Yet the puzzle remains: How
likely is it that those chemical building blocks of life would get
together to invent or find sources of energy that could fire
reproduction?
Third: why does it seem so difficult to reproduce the mechanisms of life
from scratch in our wet labs? Something to watch: Nick Lane’s lab at
University College London is working to reproduce the chemical
conditions now thought to have existed in our 4 billion-year-old seas.
Add to the puzzle the huge variety of stars and planetary
configurations we are finding in our discovery of over 3500 exoplanets.
We are only beginning to learn how diverse our universe is.
Then consider the huge variety of living species that Earth has produced
over its few billion years–how inventive evolution has been in
producing living beings as huge as dinosaurs and as tiny as prions in
every different nook and cranny on Earth, wet and dry. Reality has gone
way beyond fiction in its creative imagination, and we have only begun
to realize its extent, the depths of its potential, and how much has
already gone before us.
Looking deeper, add the amazing capabilities of simple life forms on
Earth. How did bacteria manage to invent a way to protect themselves
from nasty viruses? Soon that tool, CRISPR/Cas9, may be used to
edit–precisely!–our defective genes.
Lately we are realizing how much we humans share with our fellow
creatures on Earth. We suffer many of the same diseases as animals, have
similar cancers, heart attacks, emotional problems, sensuality, obesity
and foibles of adolescence. Don’t miss the enlightening book Zoobiquity:
What Animals Can Teach Us About Health and the Science of Healing by
Barbara Matterson-Horowitz M.D. and Kathryn Bowers, New York: Alfred A.
Knopf, 2012. Their stories remind us that life on Earth is not only
very precious and rare, but that it has many common attributes that we
should not ignore–especially if we find life somewhere else.
