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Cockroaches are known to live in very dirty places like sewers. Does this cause them to evolve to be stronger against parasites and bacteria? Recently I read online that cockroaches can sustain radioactive harm 6-15 more than humans, so does that mean that cockroaches are less likely to get cancer?

refernece for the radioactive exposure:

http://www.abc.net.au/science/articles/2006/02/23/1567313.htm?site=science/greatmomentsinscience

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It would be nice if you could add where you read that about radioactive harm. –  Armatus Jul 12 '12 at 18:55
    
@Armatus - Is that good enough? –  user5479 Jul 12 '12 at 19:01
    
Yup, thanks indeed :) –  Armatus Jul 12 '12 at 19:21
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According to Wikipedia, the most common types of cockroaches live between 6 months to two years. Humans, on the other hand, live about 70 years. Humans simply have a much longer time to develop cancer than cockroaches do. –  Andrew Salmon Jul 15 '12 at 18:46
    
@AndrewSalmon - But compare with short-lived cockroach and short-lived human, the human brain stroke rate seems to be higher since never heard of cockroach brain-stroke –  user5479 Jul 15 '12 at 21:37
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AndroidPenguin, where did you read that our immune systems are far better than those of 'a cockroach'? This seems pretty strange to me, but I'd be interested in reading a study that compared human and cockroach immune systems if you can provide a reference.

Victor, with respect to cockroaches, there are numerous species of cockroaches. Here's a page about cockroaches with a link to publications on cockroaches and a phylogenetic tree of the families and subfamilies.

http://www.bio.umass.edu/biology/kunkel/cockroach.html

All those species tend to occupy distinct niches with distinct traits. With respect to cockroach evolution, sewers are too new a phenomenon to have had an influence on cockroaches. Rather cockroaches have been successful in adapting to this novel 'habitat'. The same holds for rats and other denizens of sewers. Sewers are a very nutrient rich environment, and as in many nutrient rich environments, a few species tend to possess the right traits (whatever those may be) to survive and out-compete other species. To take an example from coral reefs, when coral reefs suffer from eutrophication, this leads to a growth in phytoplankton and a reduction of the euphotic zone that can lead to the death of all but the most resistant corals. Likewise in the terrestrial environment, only the most tolerant or opportunistic species tend to survive in highly perturbed and nutrient rich environments like sewers. With respect to cockroaches getting cancer, I've never read anything about insect cancer, but I imagine in theory that they could get cancer. I'm not sure, however, of the impact given the much shorter life spans of insects. It's an interesting question though.

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Our immune systems are more advanced. Whether that means ours is better is disputable, but specifically older organisms don't have an as well-established adaptive immune system. However of all the insects, cockroaches have one of the most robust adaptive immune systems. They produce primitive antibodies like IgM-like Ig but other immunoglobulins are much more specific to humans and allow us to fight a large range of pathogens more efficiently. Furthermore you can add advances in some of the novel immune cells we possess. –  AndroidPenguin Apr 25 '13 at 0:41
    
I'm not sure you can call a given cockroach species an 'older' organism. I would need to see a phylogenetic tree of cockroaches, but there may be species, which are younger, that is, evolved later than humans. I don't know enough at present about the immune systems of cockroaches to compare them to those of humans, but you raise some interesting points that I'd like to look into. Any suggestions on relevant publications? –  Arhopala Apr 25 '13 at 2:01
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Different pathogens affect different organisms. We live longer because we have an advanced immune system far better than that of a cockroach and because of a hundred other reasons. A cockroach that were to keep itself well fed and clean would live longer, but they can't manage that as well as they could if they had a brain as powerful as ours. Furthermore they're evolutionary suited to live in the environment they do with less consequences than we would. But look at the opposite. A cockroach and a human are in identical locked rooms with a key on the floor. The rooms have no food or water. WHo dies first? The cockroach, because the human simply walks out. For those that will be brutal, the cockroach cannot get out unless it unlocks the door because it's a cockroach escape-proof room :P

Now for your cancer question. Cancer was much rarer in the human population hundreds of years ago than it is now. That's because it's a disease you get due to damage by radiation and other mutagens over time. Cockroaches don't live long enough. But radiation isn't the only mutagen, we could feed them something if we really wanted to give them cancer. As long as cells are dividing, cells can get cancer.

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