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Although cancer rarely acts as an infectious disease, a recently emerged transmissible cancer in Tasmanian devils (Sarcophilus harrisii) is virtually 100% fatal. Devil facial tumour disease (DFTD) has swept across nearly the entire species' range, resulting in localized declines exceeding 90% and an overall species decline of more than 80% in less than 20 years.
Researchers have found that Tasmanian devils have developed some genetic resistance to the disease in just four to six generations.
Evolving resistance within so few generations is rare for vertebrates, says Beata Ujvari, an evolutionary ecologist at Deakin University in Melbourne, Australia, who was not invovled in the study. Australia's rabbit population quickly developed resistance to myxomatosis, a fatal viral infection. But it took 50–80 generations to do so.
The devil facial-tumour disease jumps from one Tasmanian devil to another when they bite each other during social interactions.
http://www.nature.com/news/tasmanian-devils-show-signs-of-resistance-to-devastating-facial-cancer-1.20508
http://www.nature.com/ncomms/2016/160830/ncomms12684/full/ncomms12684.html
(Score: 2, Interesting) by FunkyLich on Friday September 02 2016, @09:04AM
When there are less than 20% of the population that survive a disease which is 100% fatal, I would expect that these surviving individuals have a sort of immunity to it. Otherwise they would be part of the already dead 80+% of the population.
The individuals that are born from these survivors, either will contain the trait of immunity and will continue to survive, either will not and will die. But since the parents are already with a high chance of containing the trait because they are alive at a time when the vast majority of the population is dead, there is a high probability that the newborns will contain the trait as well. And thus the 'new' population that emerges will contain the imunity trait.
And a new empire will be built on the ashes of the old one.
(Score: 1, Touché) by Anonymous Coward on Friday September 02 2016, @10:45AM
AKA Evolution
(Score: -1, Troll) by Anonymous Coward on Friday September 02 2016, @01:52PM
Tazmanian Devils are hardly "evolved," they are the niggers of the animal kingdom - they are violent, destroy their habitat, and bark gibberish unintelligible by even animal standards.
(Score: 0) by Anonymous Coward on Friday September 02 2016, @11:54AM
The thing is that the trait (resistance to cancer) needs to be present in some form to evolve. This can take quite some time if it isn't present. The fact that it goes so quick suggests that the trait was already present in a subpopulation, where it took a few generations to spread through the whole population. A geneticist should then wonder, why it was already present. It could be very well be that the disease is dormant for a few decades and resurfaces then, where resistance takes up quickly and the disease is pushed back.
(Score: 1, Interesting) by Anonymous Coward on Friday September 02 2016, @01:26PM
Perhaps the thing that makes the cancer transfer is a broken gene that 80% of the population had.
If the working version gave some small advantage, that might explain why it was still around.
Hopefully they saved some samples from the broken part of the population and can figure this out with gene sequencing.
If they did not see the gene change which could take a long time, but they did see a selection given the change which was pretty quick;
then perhaps this isn't a case of 'evolving resistance' because resistance was already there.
It could be instead a case of the quick half of evolution.
If the other version of the gene hadn't already been there, and so the species had to wait for all of evolution to proceed, it seems likely that the species would not be here.
There is a lesson here in how for fast our species could change due to an unexpected biological appearance.
One hopes he necessary genes will be somewhere in the pool when the need shows up.
(Score: 2) by Joe Desertrat on Friday September 02 2016, @08:48PM
If the working version gave some small advantage, that might explain why it was still around.
It is possible that in previous manifestations of the cancer that it struck more aged animals, taking out individuals that were past prime breeding age and which had already passed on their genes. Since there are greater stresses on the population due to a variety of environmental factors, the cancer may be manifesting itself earlier now. Or, if the gene for susceptibility to the cancer is recessive, it is possible that an already struggling indigent population of the animals is forcing a smaller gene pool together. There are a lot of different factors which could account for the rise in the cancers, let us hope the remaining population has enough variability to ensure the survival of the species.
(Score: 0) by Anonymous Coward on Friday September 02 2016, @03:35PM
Maybe there is something in the environment that contributes to getting the cancer that was only scarcely present at one time, perhaps in certain locations, that is much more abundant or widespread today. Those that were exposed to it developed the gene over a few generations in the past and those genes got spread throughout the wider population to some extent as a form of remembering that this thing does or did exist in nature someplace and may resurface. In a sense you can argue it's like the population's immune system remembering something that happened a long time ago at least to some of its members and retaining some of the information necessary to survive it up to today within members of at least some of its current population.
(Score: 0) by Anonymous Coward on Friday September 02 2016, @09:35PM
I don't think there is any proof of "remembering" in genetics (in the way the immune system does it). Current models state that if a gene isn't needed any more it will converted to something more useful or will disappear over time. Keeping a "memory" costs resources to the organism, this cost reduces fitness of the individual.
The thing I mentioned above comes closest as a "memory", e.g. that a gene is retained by mild selective pressure or bet hedging.
(Score: 0) by Anonymous Coward on Saturday September 03 2016, @04:27AM
While you are generally right if a gene isn't any or that much less beneficial than another gene then it may remain in the population. There are genes that are neither beneficial nor detrimental relative to other genes, otherwise natural selection would make everyone identical.
Some people may have brown hair, some people may have black hair. In most situations hair color may not matter much but if a situation does arise where it does matter hair color could be a factor.
Another example could be butterfly color. In many situations it doesn't matter, except for when it does (ie: how well you blend into the environment and evade predators). When it doesn't matter the population may retain various colors from when it did matter.
Some characteristics from hedge betting could have been past characteristics that were at one time used for survival but aren't necessarily detrimental when compared to another surviving gene.
(Score: 0) by Anonymous Coward on Saturday September 03 2016, @04:29AM
errr ... if a gene isn't any or that much less detrimental than another gene *
(Score: 2) by butthurt on Monday September 05 2016, @04:55AM
More than 100 cases of transgenerational epigenetic inheritance phenomena have been reported in a wide range of organisms, including prokaryotes, plants, and animals.
--https://en.wikipedia.org/wiki/Epigenetics#Transgenerational [wikipedia.org]
(Score: 1, Informative) by Anonymous Coward on Friday September 02 2016, @05:08PM
Indeed. If a society shot 90% of all the tall people, after a few generations, there would be mostly short people left.
(Score: 0) by Anonymous Coward on Saturday September 03 2016, @02:25AM
They sealed off an area of territory to keep a small portion of the still healthy population disease free in Tasmania. Not sure the numbers sequestered, but I believe this population to be sizable.
They, also introduced captive-bred non-diseased animals to Maria Island (in numbers too small and a territory too small to be sustainable [without bringing in outside animals to prevent too much inbreeding; which they have not done ?yet?]). Maria Island is sort of like a large captive breeding program. Sadly, these Maria Island devils were all raised by humans, and do not behave like their wild relatives. So, even if they survive long term, they preserve the physical animal, but the social behaviors are lost-- e.g., a female was witnessed allowing multiple male devils into her den while she had pups-- a wild devil would never have allowed that. Still better than losing them completely, though.
Without doing research, I am, not sure how much of this remaining population is resistant vs. simply not exposed.
disclaimer: I am very much not an expert on devils. While in Tasmania, I went on a quest to see or at least hear a devil in the wild (before they were extinct), and spent a ton of time in the bush to accomplish it.