[Pred the Penguin]

I am suddenly reminded of The Screwfly Solution.
There are too many ways invading aliens could **** us over without even setting foot on our planet.

[Charismatic]

They forgot to add "All your base are belong to us" on the disks.

[Nuke]

we should have put a message on there demanding they surrender to the might of the terran empire

[Thaeris]

we should have put a message on there demanding they surrender to the might of the terran empire

By the time you find this device, it's already too late

 

[newman]

Matter is abundant in the universe. If they have the resources to extract our water, they have the resources to find other, easier, and perhaps more abundant sources. The unique portion of this planet is life. So long as we don't inhabit 10ⁿ of planets and claim them as our exclusive domain, then we don't even begin to make an impact on the available resources. I'll say right now that we're probably the only intelligent & advanced life in at least 20 lightyears. Considering that the galaxy is 100,000 ly wide by 10,000 ly thick, our little 20ly bubble containing 133+ stars is nothing.

If you take a bit better look at the thread you're posting in, you might actually notice that's exactly what I was saying in a previous post.
BengalTiger still thought we can't assume we won't ever become a target of an alien invasion, and I simply listed a few reasons why that line of thinking is utterly irrelevant in the long run. I still think invading us for any sort of resources would be totally ridiculous and that the whole idea of aliens wanting to invade us is totally implausible. My argument was, plausibility of an invasion aside, even if they did want to invade us, just the fact they can reach us more than likely means the technological advantage on their part would make us unable to do anything about it, making the whole point moot.

[Mars]

There is the possibility that any aliens would be as xenophobic as we are.

[newman]

In which case, it's a really, really, really big universe.

[Flipside]

What if they're similar to us biologically, they need a colony here, and Earth is just perfect?

Or what if they're some interstellar rednecks and they just declared open season in Sol?

There's plenty of more or less absurd reason why to invade a planet, and due to the fact there will be more or less absurd species living out there, some might want to find an exotic vacation place in an unpolluted world, or perhaps have a far away base for doing some dangerous experiments, keeping prisoners, or having a continent as a trade hub or repair bay...

We definitely can't assume there's no reason for invading Earth.

Biological similarity would increase the risk, not decrease it, because no matter how similar they are, all our virii and little diseases will be new to them, it would actually make them more susceptible, not less. Influenza kills millions of humans a year and we've grown up with it, imagine the impact on a society that is compatible but has had no time to develop immunities.

Edit : Now, it could be argued that an advanced race could create innoculations etc, but with each assumption we make about this hypothetical race, advanced weapons tech, biological compatability, medical and biological tech at an almost magical level etc, we are moving the bandwidth of possible threats into a smaller and smaller bracket, the odds of such a race is not impossible, but every time we add a characteristic, we reduce the chances of it existing and, indeed, the reasons to bother to invade us in the first place.

[Bobboau]

more likely the virus would find them as suitable hosts as glass. bacteria might be a problem if they are very (talking unrealistically here) similar biochemically, but there is no way a earth virus would have any idea what to do with an alien cell. virii are extremely niche evolved for their hosts, requiring specific mitochondrial structures to be built in particular ways (ect). it would be like trying to run a modern 64bit win32 application on a Setun.

[Flipside]

True, but virii also adapt very quickly, the more similar biologically, the more chance of a species jump. Incompatability would be better, though there would obviously be other aspects that would apply, like our corrosive atmosphere etc, but that incompatability would also vastly reduce the benefits of invading.

[Bobboau]

even in the astronomically unlikely event that aliens have biomolecules identifiable as sugars and amino acids, I can pretty much guaranty their equivalent to DNA will have absolutely nothing in common with ours. a virus can adapt very quickly, but I have not seen any attempts by them them to adapt to infect feldspar. if there is absolutely nothing for it to start with it will not 'try' to adapt. for instance virus do jump species periodically, but this would be things like jumping from humans to dogs, at most you will get mammals to birds, when was the last time you heard of a virus jumping from jellyfish to reptile, or from fish to person, in these situations the animals in question have about 60% of their DNA the same, an alien will most likely not even use DNA, how the hell is a virus supposed to adapt to that? that is a bigger jump than not needing a host at all.

[General Battuta]

Probably a lot more than 60% the same.

At the same time...I'm not completely ready to write off cross-species pathology. Convergent evolution may produce biochemical congruities, and any pathogen that works on a congruent locus may be able to cross.

[Bobboau]

except viruses work by inserting themselves into a DNA strand and having the host machinery do the work of replicating them, if the host machinery doesn't even use DNA how is a virus supposed to deal with that?

[General Battuta]

Sorry if I was unclear.

At the same time...I'm not completely ready to write off cross-species pathology. Convergent evolution may produce biochemical congruities, and any pathogen that works on a congruent locus may be able to cross.

DNA is extraordinarily effective as an information store and a computational medium. I meant to imply that convergent evolution may produce it or a storage molecule that shares at least some processes.

[Bobboau]

I'm not saying it isn't but I think its unrealistic to assume that it is the only good solution possible, and starting from scratch it would be the only one to arise.

[General Battuta]

On the one hand, I intuitively agree with you. On the other hand, with amino acids similar to those that form the building blocks of life on Earth popping up in comets and distant nebulae, it may be that the fundamental ingredients are universal and that the structures we see are the optimum result.

I'm just trying to consider all possibilities here.

[Flipside]

It depends if we are talking about similar or dissimilar creatures, one could hardly describe Feldspar as something that could catch a disease, this is true, but we are dealing with two dissimilar situations here, situation A is similar life forms that can exist in our environment without modification or with very limited protection, the other is an entire different form of life that requires extensive adaptation to exist in an Earth-like environment.

With similarity there are a number of questions that simply cannot be answered, such as 'how similar?', can they injest our food? Can they metabolise water? If the answer is yes, then I would have thought there would be a strong possibility they would be just as susceptible as humans to the piggy-back bacteria involved in those activities.

[Bobboau]

the only thing the 'similar' about the creatures you describe there is they have a tolerance for oxygen and have a water based biochemistry. if they can eat our food then it would imply the reverse would be possible, so they would have to worry about bacteria, but my main contention was viruses.

[karajorma]

On the one hand, I intuitively agree with you. On the other hand, with amino acids similar to those that form the building blocks of life on Earth popping up in comets and distant nebulae, it may be that the fundamental ingredients are universal and that the structures we see are the optimum result.

Very, very doubtful. There's no particular reason that DNA has to be based on that particular set of nucleotides and sugars. Given the number of similar chemicals it's probably simple chance that we've ended up with this particular set rather than any other equally good set. And that's making the assumption that something like RNA is needed as a precursory replicator. If it isn't then it becomes even more doubtful.

Then you have to consider how the **** they're getting to the alien's DNA in the first place. This isn't a matter as simple as just ambling through the cell wall you know. Virii have spent millions of years getting very good at passing through cell walls. With an alien all that adaptation would be useless.

Bacteria are a completely different issue cause they can survive and reproduce quite well outside of the body but virii are parasites. I have a hard time believing that they could infect an alien species. They'd have to be far too similar.

[General Battuta]

On the one hand, I intuitively agree with you. On the other hand, with amino acids similar to those that form the building blocks of life on Earth popping up in comets and distant nebulae, it may be that the fundamental ingredients are universal and that the structures we see are the optimum result.

Very, very doubtful. There's no particular reason that DNA has to be based on that particular set of nucleotides and sugars. Given the number of similar chemicals it's probably simple chance that we've ended up with this particular set rather than any other equally good set. And that's making the assumption that something like RNA is needed as a precursory replicator. If it isn't then it becomes even more doubtful.

Then you have to consider how the **** they're getting to the alien's DNA in the first place. This isn't a matter as simple as just ambling through the cell wall you know. Virii have spent millions of years getting very good at passing through cell walls. With an alien all that adaptation would be useless.

Thanks, but I'm fluent in the biological sciences and I think the fundamental point, that congruent loci could conceivably produce congruent vulnerabilities, may stand. This isn't a strong stand for the position, just an acknowledgment that it might occur, particularly if the hazy bits of your argument (probably; uncited 'no particular reason'; chances are) don't go the way we both think is more probable.

All life on Earth is derived from common stock and the level of genetic similarity is staggering, with humans in particular being quite homologous. Obviously something derived from a different root might differ enormously. But the possibility of strong convergence exists.