Miss Anne Thrope

Okay, two quick questions for you good people, since I've no idea where else I might find this information. The first is a question regarding evolution, so I think it's better here than in Science and Skepticism.

Question the 1st - Nevermind the obscene cost of actually achieving such, it may eventually be possible to construct artificial enclaves of life on planets, comets, or whatever around a neighboring star. If we were careful enough and had the correct technology, I imagine we could send these colonists to their new homes completely free of pathogens and parasites, leaving only overtly benign or helpful bacteria in the digestive system. But I wonder if this is a good idea. How long before one strain or another of that bacteria evolves to fit all those empty ecological niches?

Question the 2nd - I read somewhere that perhaps up to a quarter of an animal's mass is bacteria. If this is correct, would a person living in the enviroment described above have 25% less bulk, or would the resources that would have gone elsewhere be utilized by the body?

I wonder about these things. Thanks.

Jet Black

I think it would be a terrible idea. there is bound to be a mutation in something at some point, and all those weak underused immune systems will really suffer for it.
but I do know that there are quite alot. Many of them are also symbiotes, and you wouldn't want to get rid of those

Miss Anne Thrope

But wouldn't a newly mutated dangerous bacteria be at a severe disadvantage? It'd be like starting the evolutionary arms race between pathogen and host from the very beginning, with the only difference being that people have already evolved means of countering previous forms of disease. Sure, the immune system would be weakened drastically were we free of disease, but could a weakened immune system not defend against fledgling mutations from what were once benign bacteria and/or symbiotes?

Oolon Colluphid

No, not really. Whatever mutations turn up, only those able to survive in the already-existent immune system will prosper. Sure, most will be knocked off straight away. But once a lineage starts that can survive -- at the host’s expense -- then the immune system will constantly be playing catch-up.

Cheers, Oolon

Jet Black

some mutations can be really nasty. there is no necessity for a parasite to get progressively more parasitic. In fact the converse is generally true. Parasites usually get less parasitic, because more are likely to survive if they don't kill the host, and even more still if they help the host (and become symbiotic). An example of a sudden appearance of a pathogen might be E-Coli strain 151, which appeared in the UK a while ago and killed a few people. arms races only usually occur over organisms that are actively trying to kill one another.

Oolon Colluphid

Depends, though, on the means of transmission. If the host's survival is irrelevant to the parasite getting passed on (like one that gets into water supply through feces, so the host shitting themselves even unto death is good for the parasite)... or if killing the host actually helps (like getting from one host to another by the other host being a scavenger), then it might, contra the logic of your argument, evolve more virulence. The answer is, 'depends'. Have a Google for 'evolution of incresed virulence'. (Though I imagine you're aware of this sort of thing JB!)

Miss Anne Thrope

This sounds no different than what occurs right this moment. How would this be different in the enviroment I described earlier? With only benevolent symbiotes in the equation with plenty of nearby empty disease niches waiting for a mutation. How long until we'd start getting full fledged dangerous microbes?

Oolon Colluphid

The difficult thing about niches (<singing> Is niches are difficult things / Their sides can be bendy as rubber / There’s even some in the hot springs </singing>)

Ahem, excuse me...

... is that while they may be sitting there in Dawkins’s ‘Animal Space’, it’s not necessarily easy to get to them. There might be, for instance, an unexploited niche for pigs with wings... but no practical route via small steps to it. Parasitism is at the end of a sliding scale of inter-species interactions. Any well adapted symbiotic bacterium that varies from its ‘good guy’ role may well get punished by selection -- ie there may be selection pressure to remain ‘nice’, and no way to start exploiting the host again.

OTOH, bacteria are notorious gene-shufflers. Given their numbers and generation time, big mutations are not vastly unlikely... am I waffling? I think the answer is “it’s anyone’s guess! Let’s run the experiment...�?

Oolon

Miss Anne Thrope

Oolon and Jet Black, I appreciate your responses. Thanks!

Peez

<singing> But the most difficult thing about niches is / they're different... for every-one! </singing>

Peez