Mirror Life Worries
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The article discusses the concept of 'mirror life', a hypothetical form of life with mirrored biochemistry, and the potential risks associated with creating such life forms, sparking a discussion on the dangers and implications of such technology.
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if it did I would have thought it would have appeared in the past 5 billion years or so
It may have appeared and been outcompeted. That doesn’t suggest its (artificial) reintroduction would again be outcompeted
Now, with L-amino life everywhere it would have an even bigger starting problem.
We see this with extremophiles: organisms which can grow in nuclear cooling ponds full extremely badly when transplanted to nutrient rich environments with other, less capable organisms.
It's possible that humanity could survive by exploiting things like fossil fuels but by default it would be as bad as the extinction that ended the Permian. And certainly most humans would die.
We're protected from this naturally because it takes over a billion years to evolve something as good at reproducing as cyanobacteria from scratch and any biogenisis that were to happen in the modern world would produce something so hapless it would be swiftly out competed for resources. You can't evolve from a regular bacteria to a mirror bacteria, evolution is really bad at making multiple changes at once and this would require changing literally every part of an organism at once.
I am not alarmed by the possibility of mirror life because I think it would be at a disadvantage to all other life on earth at present, so it probably wouldn't get very far. (famous last words!?)
That's the problem. Mirror life may not be a problem for the biosphere in the long run but it could totally be a problem for humans in the short run.
Mirror life can only use the fats and a few amino acids of the normal life. All sugars have chirality so they would need some enzymes to east their own mirrored sugars and another set of enzymes to eat normal sugars. Also, most amino acids have chirality and they would have to reverse them or make their own.
So even if someone waste a few gazillions dollars to make mirror life, it would not be able to eat most normal food.
Until mirrored life evolves enzymes to eat non-mirrored sugars, mirrored life will be at a large disadvantage.
But with exposure to our environment, replete with non-mirrored sugars, that sets up a large evolutionary pressure in the direction of finding those enzymes, in addition to the mirrored enzymes they will already have for eating mirrored sugars.
With such evolutionary pressure, it seems plausible mirrored life will evolve those enzymes, even though non-mirrored life appears not to have done so, or at least not retained it. Because there has been no equivalent evolutionary pressure for non-mirrored life to eat mirrored sugars.
If mirrored life does evolve those enzymes, due to that asymmetric evolutionary pressure, then instead of being at a disadvantage, it might give them a temporary advantage over non-mirrored life.
Also cellulose and starch are very similar, they are chains of glucose, but bounded slightly different. We can split only starch, but we don't have enzymes to split cellulose, were "we" includes cows and a lot of animals that would really love to digest cellulose.
I think some bacteria can digest weird sugars, even the mirrored versions, but they are more efficient digesting usual sugars.
Until mirrored life evolves enzymes to eat non-mirrored sugars, mirrored life will be at a large disadvantage.
But with exposure to our environment, replete with non-mirrored sugars, that sets up strong evolutionary pressure in the direction of finding those enzymes, in addition to the mirrored enzymes they will already have for eating mirrored sugars.
With such evolutionary pressure, it seems plausible mirrored life will evolve those enzymes, even though non-mirrored life appears not to have done so, or at least not retained it. Because there is no equivalent evolutionary pressure for non-mirrored life to eat mirrored sugars.
If mirrored life does evolve those enzymes, due to that asymmetric evolutionary pressure, then instead of being at a disadvantage, the ability to eat both types of sugars might give them a temporary advantage.
Anyway, Peter Watts' Rifters series is another excellent take on the genre, although it's not mirror life per se. (And it's ... not a happy read.)