A Second Tree of Life…or Death?

What’s your favorite version of the Apocalypse? Armageddon? The Rapture? Or perhaps catastrophic climate change is more your cup of tea. If you’re over 65, it might be AI; if you’re under 30, it might be zombies.  

Carl Zimmer’s recent column (New York Times, 12/12/2024) offers a new candidate. According to Zimmer, scientists are “a few decades” away from creating a novel microbe that would essentially amount to a Second Tree of Life. Zimmer reports: 

“Within a few decades, scientists will be able to create a microbe that could cause an  unstoppable pandemic, devastating crop losses or the collapse of entire ecosystems.” 

Zimmer understates the problem! Perhaps he did not want to create panic. Crop failures  and the attendant global famine are the least of our problems. The creation and  ‘deployment’ of a second form of life would likely wipe out all current life forms in very  short order. Bummer! 

How come? The primordial DNA/RNA molecule synthesized about 4 billion years ago; it  quickly blanketed the planet with unicellular organisms (prokaryotes such as bacteria). If  any other self-replicating molecule synthesized before or after, all traces of it have been  obliterated. Genetics takes no prisoners! 

If mad scientists or curious aliens ever succeed in releasing an alternative self-replicating molecule into our biosphere, it is unlikely that the two forms of life could long co-exist.  Undeterred by such risks, we are hard at work searching for life elsewhere in the Universe.  

We worry, will the aliens be friendly? Who cares! If they consist of self-replicating  molecules that cannot coexist with DNA/RNA, their mere arrival on Earth could doom our  planet. But don’t lose sleep over this. In all probability, there are no ‘little green men’ in the  skies above us; and if there are, they’re nowhere to be seen. 

A bigger threat is posed by our own laboratories (think COVID 19), experimenting with  silicon and other ‘inorganic’ elements, hoping to discover the key that unlocks Pandora’s  Box. Fortunately, they face some significant hurdles.  

Silicon, for example, behaves a lot like Carbon in some situations but in other ways (its  water solubility, the strength of its chemical bonds, and even the angles of tangency  among its atoms), it’s quite different. So there’s no need for cold sweats on this account  either…yet.

Zimmer is reporting on a threat that is much more imminent: “Our DNA…has a backbone  made partly of sugar. While sugar molecules can exist in left- and right-handed forms, DNA  only uses the right-handed molecules. That’s the reason DNA’s double helix has a right handed twist. Our proteins, by contrast, are made of left-handed amino acids. This  combination is found not just in humans, but in every species on Earth.” 

What if scientists are able to ‘reverse that chirality’? What if they synthesize left-handed DNA? (We have already created right-handed amino acids!) We know what happens when we ‘reverse the charge’ of an elementary particle: If it comes in contact with a traditionally charged version of itself, the particle pair will self-annihilate in a flash of pure energy. There is every reason to believe that this would be true of chirality-reversed molecules as well. 

Biblical scholars among us will recall that the Garden of Eden included two sacred trees, the Tree of Life and the Tree of Knowledge. By tasting the forbidden fruit of knowledge, humanity compromised its relationship with life itself. We are mortal now, we suffer, but life goes on…at least for now. 

Are we about to make the same mistake again? In our zeal to stretch the envelope of gnosis are we willing to put bios itself at risk…again? It’s assumed that we can’t help ourselves. Since we were little children, we have instinctively opened every cabinet door, raised the lid on every box, pulled every dangling string or chain. Cajoling parents, armed with threats and draconian punishments, are powerless against native curiosity. What makes anyone think we’ll stop now? 

Knowing that we’ll probably find some way to destroy terrestrial life as we know it, we need to place our precious DNA molecule in a museum or wildlife refuge. We must ensure that it does not come in contact with its chirality reversed alter ego. What better protection than a moat, as wide and deep as we can make it, connected with the mainland only by a single strand of thin wire! What better moat than interplanetary space! 

Hence, the current focus in the USA, China, India, Japan and the EU on space travel. Our first DNA sanctuaries will be on our Moon and on Mars. Eventually, we will establish other conservation sites on selected moons of Jupiter and Saturn. Beyond that, the sky, quite literally, is the limit! 

If ‘life on Earth’ is only one of nature’s many bio-initiatives, it may still be worth preserving our DNA, if only for historical research and scientific experimentation. But if our life form is the only life form in Universe, failure to protect it would be truly catastrophic. 

We are perhaps only a decade or two away from building an archipelago of self perpetuating DNA colonies. Let’s hope we make it in time; the stakes quite literally could not be higher.

*****

Image: "The Tree of Life." First half 17th century. British. Canvas worked with silk thread; tent, Gobelin, and couching stitches. H. 22 1/2 x W. 24 1/8 inches (57.2 x 61.3 cm). Textiles-Embroidered. Gift of Irwin Untermyer, 1964.

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