In HG Wells classic “War of the Words”, Martians invade the earth. They are highly technically advanced, so much so that they are destroying human life-earthian armed forces are no match for them. Just when things look hopeless, the Martains start dying-killed by bacteria which invade them (and for which they have no immunity).
Now, suppose that we are visited by alien beings-how likely is it that our disease germs would find them tasty?:eek:
Exceedingly unlikely: viruses - impossible, they work by modifying DNA, and the chances that an alien biosystem would have evolved exactly the same gene structure (or even DNA itself) seem infinitesimal. Bacteria? Maybe, but again they co-evolved with terrestrial life forms, and would probably not be able to multiply in a non-terrestrial host, and if they did, the toxins produced might not be toxins to the host (especially if said host isn’t carbon-based or has no “pumping fluids” to distribute pathogens).
Since we have no way of knowing what physiology alien beings would have, the question is unanswerable.
Nitpick, but an important one: They weren’t killed off by disease germs, but by the microbes responsible for decomposition. Disease germs tend to be very specific as to what they’ll attack, but rotters will eat just about anything that doesn’t fight back.
It’s impossible to say without more data, but in my opinion it’d be exceedingly unlikely.
How about your mom’s cooking?
::d&r::
Why? Assuming that the Martians aren’t based on silicon (unlikely) or breathe chlorine gas (also unlikely), then they probably have metabolisms that use the same kinds of yummy sugars and proteins that we do. The Martian immune systems, assuming they have them, wouldn’t ever have seen Earth microbes. It’s actually a pretty likely end to an alien invasion – they wouldn’t necessarily come down with diseases so much as get eaten alive by scavenger microbes.
Seems to me if they were biologically similar enough to us that Earth bacteria could do them in, then the Martian bacteria that they brought with them would do us in as well. So whether Wells was right or wrong, we’re screwed. 
I think Wells tried to eliminate that possibility by describing the Martians as having wiped out such bacteria on their own planet some time ago IIRC.
Exceedingly unlikely.
First off, as far as we can see life here uses carbohydrates as the result of an accident. It is reasonable to assume that any life that evolved in a similar environment would use an energy source consisted of some combination of hydrocarbon and water. However the chances that it would evolve a specific configuration with an aldehyde group on one end and an alcohol on the other is remote to say the least. There are thousands of other configurations that would be just as effective as an energy store.
Even if such lifeforms did evolve carbohydrates, most organisms on Earth can’t even digest most of the carbohydrates on Earth, so the chances of a life form from another planet being able to do so are remote, to say the least. There are some approximately universal carbohydrates on Earth, such as one isomer of glucose, but as far as we can tell that’s entirely the result of common early heritage. Outside of that, well even the isomers of sucrose are indigestible to most, never mind the odd sugars such as lactose or the complex carbohydrates such as starches and cellulose.
Probably an organism from another planet would use an energy source consisting of a right handed isomer of a carbon chain with an ether in the middle, a carboxylic acid on the other an alkane on the other. Totally indigestible by anything on Earth.
The chances of another lifeform using digestible proteins is even more remote, to the point where if hey did it would be compelling evidence of common ancestry. Proteins are pretty improbable enzyme systems, and almost anything else would work just as well, such as system using chlorine instead of metal of halide instead of nitrogen groups. Even if another life form did use nitrogen in its enzymes, the odds of them having the same configuration as an amino acid is infinitesimally small.
The only macronutrient that is likely to be universal is lipids. Triglycerides may be indigestible, but basic fats seem likely to be produced by any terrestrial lifeform. The advantages of having a hydrocarbon with a water soluble end is just too obvious for it not to have evolved pretty much everywhere.
And that is where the microbes are likely to become universally infective. The ability to digest lipids means that they can live on the skin of any organism, and ultimately destroy the cell membranes of any creature. To me the idea of contracting a fatal infection from another lifeform seems almost certain for this reason.
Well, that depend so the immune system. Even close relatives of our like jawless fish have wildly different immune systems. There’s lots of different ways to fight infection each with its own advantages.
The real problem is that there’s no way to defeat the infection even if the immune system does mount a defence. If there are no proteins and no carbohydrates then most immune systems won’t be able to lock onto it. We rely on the recognition of proteins and sugars to identify non-self. If something lacks those structures then we tend to ignore it, which is why polymer or even cellulose implants pose absolutely no immune risk. Even if it could lock onto the microbes, then what? It can’t possibly have the enzymes to digest the non-protein non-carbohydrate structural elements, and it’s implausible that any organism is going to be flooding its system with generic lipases that will digest its won flesh.
Meanwhile the microbes will be getting all the energy they need by digesting cell membranes and feeding on the the mineralised nitrogen and phosphorus that is released by the dying cells. the microbes will have no trouble digesting the Martians and getting all the nutrients they need. It’s implausible that the Martians will have any way at all of digesting the microbes.
More than that – Wells clearly implies that the Martians had done themselves in by kiling off all their own harmful bacteria, and this left themselves vulnerable to other bacteia, since their own immune systems weren’t used to dealing with the problems.
Could our bacteria wipe out an invading alien? I don’t see why not. our bacteria certainly wouldn’t be optimized to eating alien meat (so to speak), but that doesn’t mean it wouldn’t be edible. In fact, it might be super-edible. It’s often said that a successful parasite doesn’t kill its host, but that’s for a situation where both evolve together. Throwing perfectly edible food into a situation with no countermeasures is asking for a biological massacre. It seems a perfectly possible (although not likely) scebario to me.
If we ever do make contact with some alien race, it’d probably be a good idea to make lots and lots of tests just to be sure there’s no danger to either one from the other’s microbes. Yes, it may not be likely, but does anyone want to bet their species on that likelihood? I don’t think so.
So lets first expose some lab animals to the other guys’ bugs before shaking manipulative appendages or whatever.
I think history tells us this is a very likely scenario. There are numerous examples throughout history of non-native species being introduced to an ecosystem without natural predators, multiplying without limit, and nearly destroying the native species. I think it’s very likely that something on Earth would be harmful to aliens, and that something is probably not as harmful to humans. My bet would be the atmosphere itself. Our atmosphere is mainly nitrogen and oxygen. I wouldn’t be surprised if either one is either toxic to an alien race, or the gas that an alien race needs to breathe is not one of them.
Regarding bacteria or viruses, I agree with the previous posters, that it depends on their metabolism. However, I saw a show on one of the nature channels about harmful fungi, and that seems like a more likely source.
I didn’t remember that at all - thanks.
Unfortunately it’s wrong.
Prolly not, though, even leaving aside that they had killed off their own. They would have brought very few in total, and those might easily have been utterly overwhelmed by the local buggers. Sure, a few might spread, but those are unlikely to be exactly what could hurt us. I can believe it’s very possible one of the billions of earth nasties could get at the aliens than one of a relative handful of alien microbes could get at us.
In a nutshell, I think that if we ever do run into life out there, it would be a coincidence on a cosmic scale to find that we shared more than a few common molecules in our biochemistries. My opinion is that we’ll find that there are far more solutions to the problems of life than the ones that happened to pop up here on Earth. I could be wrong, of course, but we won’t know until we collect some data.
It’s also perfectly possible that Marslife and Earthlife would share a common ancestor. It’s less likely that life in other solar systems would share a common ancestor but it’s possible as well. So Martians might be as closely related to humans as humans are to bacteria.
It seems to me that if the alien biosphere is unrelated to the earth biosphere the big problem won’t be alien microbes but just general toxicity. God knows what kind of chemical compounds the alien life will be putting out. Heck, most parts of our own planet will kill an unprotected human in a few hours.
But I think we’re assuming that aliens are smart enough to not wander around in our toxic atmosphere unprotected, any more than we’d land on another planet without space suits.
What about the possibility of some kind of allergic reaction? Maybe to longhaired cats. The aliens could be defeated with a simple catapult device.