The Speculist

The New York Times published an Op-Ed yesterday from Paul Davies, astrobiologist and author of many books including The Fifth Miracle: the search for the origin of life.

One tenet of evolutionary biology is that all life on Earth is related - that all plants and animals all the way down to microbes are descended from a single instance of bio-genesis about four billion years ago. Dr. Davies is not so sure.

...Huge asteroids and comets mercilessly pounded the planet, creating conditions more reminiscent of hell... The biggest impacts would have swathed our globe in incandescent rock vapor, boiling the oceans dry and sterilizing the surface worldwide.

How did life emerge amid this mayhem? Quite probably it was a stop-and-go affair, with life first forming during a lull in the bombardment, only to be annihilated by the next big impact.

If life got started more than once, then Earth once harbored life very different from what we know today. It might have been as alien as anything light years away. These microbes could still be here with biologists overlooking them everyday.

Under a microscope, many microbes appear similar even if they are as genetically distinct as humans are from starfish. So you probably couldn't tell just by looking whether a microorganism is "our" life or alien life. Genetic sequencing is used to position unknown microbes on the tree of life, but this technique employs known biochemistry. It wouldn't work for organisms on a different tree using different biochemical machinery. If such organisms exist, they would be eliminated from the analysis and ignored. Our planet could be seething with alien bugs without anyone suspecting it.

Davies suggests a simple and inexpensive experiment that could prove the existence of these native aliens. Life as we know it uses left-hand amino acids. Mirror image right-hand amino acids exist, but are useless to known life. Biologists believe that life could work just as well with those bizarro amino acids, it's just that familiar life went left.

If life started more than once, there's an even chance that it uses right-hand amino acids. Davies suggests preparing a dish of anti-food, place any unusual microbes you might find in the dish and wait. If it grows it would be a very big deal.

The discovery of a second sample of life on Earth would confirm that bio-genesis was not a unique event and bolster the belief that life is written into the laws of the cosmos. It is hard to imagine a more significant scientific discovery.

This wouldn't answer the question of whether complex or sentient life exists elsewhere, but it would convince most scientists that microbial life is common in the universe. And this discovery would certainly move the Foresight Exchange.