Aliens Among Us

In a remarkable article in the Scientific American, Paul Davies reports on scientists’ pursuit of evidence that life arose on Earth more than once, providing evidence for a plethora of life in the universe.

“The origin of life is one of the great unsolved problems of science,” writes Davies. “Nobody knows how, where or when life originated. About all that is known for certain is that microbial life had established itself on Earth by about three and a half billion years ago. In the absence of hard evidence of what came before, there is plenty of scope for disagreement.”

And a plethora of disagreement there is.
Earlier existentialist notions that life resulted from a chemical fluke so improbable it would be unlikely to have happened twice in the observable universe are being challenged by more optimistic views that the universe is teaming with life. In 1995, biochemist Christian de Duve declared that life was “bound to arise” on any Earth-like planet. Robert Shapiro of New York University agreed with de Duve’s “cosmic imperative” for life to exist and suggested that this “biological determinism” is “written into the laws of nature.”

How can we prove biological determinism? Well, checking for life on other planets like ours would be the most direct way. Unfortunately these sorts of sophisticated missions may take a while. Impatient for answers, scientists came up with the notion that Earth itself may reveal answers: if life emerges readily under terrestrial conditions, then perhaps it formed many times on our planet. Scientists began to search exotic extreme and isolated environments like deserts, scalding volcanic vents, deep caverns, or the dry valleys of Antartica for evidence of “alien” life forms—organisms that would differ fundamentally from all known living creatures. Such “extremophiles” could survive in salt-saturated lakes, highly acidic mine tailings, and waste pools of nuclear reactors.

Davies goes on to describe a “shadow biosphere” (coined by Carol Cleland and Shelley Copley of the University of Colorada) which describes alternative life-forms that have survived and are still present on Earth. Making up part of a large microbial world, this “shadow life” may have easily been overlooked by scientists, says Davies. Some scientists are suggesting that “shadow life” may even share the same general biochemistry with familiar life but use a different set of amino acids or nucleotides to store information. Steve Banner of the Foundation for Applied Molecular Evolution uses the field of synthetic or artificial life to study and engineer new organisms by inserting additional amino acids into proteins. Astrobiologists have long speculated on forms of life in which some other solvent (such as ethane or methane; found on Titan, Saturn’s largest moon) replaced water. Another popular notion is that different elements (other than carbon, hydrogen, oxygen, nitrogen and phosphorus) constituted the life form.

I am Particularly intrigued by the observation that, while all known organisms manufacture proteins from amino acids using large molecular machines called ribosomes, some autonomous (self-reproducing) have been identified. An example of this is the controversial discovery of Philippa Uwins of the University of Queensland who found “nanno-bacteria” in a deep-ocean borehole off the coast of Western Australia.

Davies concludes by saying that “it is clear that we have sampled only a tiny fraction of Earth’s microbial population. Each discovery has brought surprises and forced us to expand our notion of what is biologically possible. As more terrestrial environments are explored, it seems very likely that new and ever more exotic forms of live will be discovered. If this search were to uncover evidence for a second genesis, it would strongly support the theory that life is a cosmic phenomenon and lend credence to the belief that we are not alone in the universe.”

...I could have told him that...

Nina Munteanu is an ecologist and internationally published author of novels, short stories and essays. She coaches writers and teaches writing at George Brown College and the University of Toronto. For more about Nina’s coaching & workshops visit www.ninamunteanu.me. Visit www.ninamunteanu.ca for more about her writing.