Mirror-Image Cells Could Transform Science — or Kill Us All | Hacker News Reader

Mirror-Image Cells Could Transform Science — or Kill Us All

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27 pointsVMG14 comments

It won't wipe out humanity, just potentially plankton-dependent life.

Also, it's not quite so easy to construct a whole mirror cell. The Venter Institute managed to produce viable synthetic DNA, but that still needed a natural host cell to provide the cytoplasm and other cell mechanisms. You can't do that with mirror molecules, you'd have to build it whole, in one go.

As far as we know, building mirror life would be a feat of nanotechnology rather than chemistry or genomics.

Surely humanity is arguably plankton-dependent?

Not strictly speaking. There would be serious consequences, but not a human extinction.

A phrase like "not strictly speaking" gives the impression that you would be qualified to elaborate on that point. Don't hold back.

I would assume that it would basically wipe out most of the life in the sea. But of course, we don't need fish to live.

I'd rather keep 'em though, personally.

No plankton means no oxygen planet-wise (forests provide zero or negative oxygen yield) as far as I know.

"forests provide zero or negative oxygen yield"

Do you know of a resource you can point to about that topic?

No, a quick google search shows that most resources think that 20-70% of the world's atmospheric oxygen comes from trees.

Killing oxygen-breathing life in the ocean, with nothing to replace it, would increase the proportion of oxygen in the atmosphere, to the detriment of CO2 and methane. This would have potential implications for the climate at large (a faster and longer ice-age than usual). But it would be a slow enough process that the human race could survive (if nothing can be done about the mirror life itself).

On the shorter term, the damage to sea-borne life would impact humanity's food supplies, by how much is not clear because land-based agriculture can be ramped up.

I am certainly not qualified to speak as an expert, but neither are most people here.

Basically, we don't know what would happen. We might wipe out plankton-dependent species. That would obviously have serious ecological consequences.

I thought that the idea was to hack ribosome to do some sort of cross-compilation. So not exactly "have to build it whole in one go". Sure, still very difficult.

There seems to me to be a missing step there; I don't get how mirror bacteria somehow automatically hoover up all the resources. They'd be in competition with the normal bacteria, and it is not immediately obvious to me why they so automatically win. Because, again, this is a mirror competition, so whatever putative advantage the flipped version has, the normal version has, along with overwhelming starter advantage. It seems to me there's only really two possible resulting outcomes, based on symmetry arguments: The flipped versions still die out, because life favors the already-dominant hand for some reason, or they compete themselves into a 50/50 standoff because the forces don't favor either side once they reach parity. Life favoring the side with the numerical advantage and crushing the other side also happens to explain why we have one-handed life, so arguably it's the dominant hypothesis at the moment, too, though I wouldn't care to bet the fate of the planet on it.

Now, the bad thing about the 50/50 case is that it may be a much, much lower-energy biosphere, because now all life has to deal with the existence of proteins it can't do anything with and absolutely nothing is evolved to deal with. Could still be a holocaust of epic proportions with the biosphere not really recovering for several million years and almost all non-directly-photosynthesizing life wiped out by starvation as the biosphere has to rebuild from the bottom. (And by "biosphere recovering" I still mean that we're basically wiped back to the Great Oxygenation Event [1] in complexity terms, assuming there's nothing we can do to fix it after the fact.) Could be a disaster, certainly. But I still don't get the claim that it would somehow automatically utterly outcompete the existing biosphere.

[1]: http://en.wikipedia.org/wiki/Great_Oxygenation_Event

Wouldn't life favor the flipped version because it has no natural predators? Consider it an invasive species [1], something there are many examples of and usually a serious problem. While life may favour existing right-handed life over developing left-handed life, this does not mean it will favor existing right-handed life over developed left-handed life - the argument is akin to saying that an invasive species cannot dominate because it hasn't evolved into place already.

[1]: http://en.wikipedia.org/wiki/Invasive_species

Ah, yes, maybe that is what I'm missing. Mentally I have a hard time seeing bacteria as something that can be preyed upon, but there's nothing impossible about that, of course, what with the way it happens and all.

(Like so many "tipping point"-type arguments my gut still says that if there wasn't an advantage to having us all on the same hand, particularly the ability to pick up correctly-handed molecules out of the environment and use them, that we'd already live in a 50-50 world; if the system is that vulnerable to tipping it would already be tipped, so a small dribbling of cyanobacteria in the ocean will probably simply result in the mirrors dying off. If life is as easy to start up as it seems to be, it seems like at least once a mirror life form should have started up. But that's a plausible line of reasoning, not anything like a proof.)

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