|Tasmania devil Sarcophilus harrisii|
A little over 30 years ago, Tasmanian devils, marsupials that lives only on the Australian island of Tasmania, began to develop fatal tumours on their face. It was subsequently found that this devil facial tumour disease (DFTD) was a transmissible cancer which is passed on when one animal bites another on the face and transfers live tumour cells to the new host.
It is thought that these transmitted cells are not recognised by the devils' immune system as foreign and so destroyed because they are genetically so close to the devil's own cells having developed in a highly in-bred population as the population declined and genetic diversity declined with it. Ironically, a parasite has arisen in a host, derived from the host itself.
The only other transmissible cancer previously know is the canine transmissible venereal cancer (CTVC) in dogs. This cancer is transmitted during mating and also shows signs of having evolved recently in evolutionary terms (about 11,000 years ago) in an isolated and inbred population of dogs close to huskies and Alaskan malamutes for much the same reason as DFTD arose in Tasmanian devils.
Now, as though that itself isn't difficult enough for intelligent (sic) design creationists to explain (why design Tasmanian devils then kill them off by designing a transmissible cancer their immune systems can't recognise?) a team of researchers led by Ruth Pye of the Menzies Institute for Medical Research, University of Tasmania, Hobart, Tasmania, Australia, have discovered that there are actually two different forms of this disease, grossly morphologically indistinguishable but genetically and histologically distinct. Transmissible cancer appears to have arisen twice in Tasmanian devils, and probably within the last 30 or so years.
Transmissible cancers are somatic cell lineages that are spread between individuals via the transfer of living cancer cells. Only three transmissible cancers have been reported in nature, suggesting that such diseases emerge rarely. One of the known transmissible cancers affects Tasmanian devils, and is threatening this species with extinction. Here we report the discovery of a second transmissible cancer in Tasmanian devils. This cancer causes facial tumors that are grossly indistinguishable from those caused by the first-described transmissible cancer in this species; however, tumors derived from this second clone are genetically distinct. These findings indicate that Tasmanian devils have spawned at least two different transmissible cancers, and suggest that transmissible cancers may arise more frequently in nature than previously considered.
Clonally transmissible cancers are somatic cell lineages that are spread between individuals via the transfer of living cancer cells. There are only three known naturally occurring transmissible cancers, and these affect dogs, soft-shell clams, and Tasmanian devils, respectively. The Tasmanian devil transmissible facial cancer was first observed in 1996, and is threatening its host species with extinction. Until now, this disease has been consistently associated with a single aneuploid cancer cell lineage that we refer to as DFT1. Here we describe a second transmissible cancer, DFT2, in five devils located in southern Tasmania in 2014 and 2015. DFT2 causes facial tumors that are grossly indistinguishable but histologically distinct from those caused by DFT1. DFT2 bears no detectable cytogenetic similarity to DFT1 and carries a Y chromosome, which contrasts with the female origin of DFT1. DFT2 shows different alleles to both its hosts and DFT1 at microsatellite, structural variant, and major histocompatibility complex (MHC) loci, confirming that it is a second cancer that can be transmitted between devils as an allogeneic, MHC-discordant graft. These findings indicate that Tasmanian devils have spawned at least two distinct transmissible cancer lineages and suggest that transmissible cancers may arise more frequently in nature than previously considered. The discovery of DFT2 presents important challenges for the conservation of Tasmanian devils and raises the possibility that this species is particularly prone to the emergence of transmissible cancers. More generally, our findings highlight the potential for cancer cells to depart from their hosts and become dangerous transmissible pathogens.
Ruth J. Pye, David Pemberton, Cesar Tovar, Jose M. C. Tubio, Karen A. Dun, Samantha Fox, Jocelyn Darby, Dane Hayes, Graeme W. Knowles, Alexandre Kreiss, Hannah V. T. Siddle, Kate Swift, A. Bruce Lyons, Elizabeth P. Murchison, and Gregory M. Woods
A second transmissible cancer in Tasmanian devils
PNAS 2015 : 1519691113v1-201519691. doi: 10.1073/pnas.1519691113
So then, what intelligent (sic) design advocates need to explain is how this rates as intelligent. Accepting for the sake of argument that there is no such thing as evolution and everything is designed by an intelligent designer, what we have here is a species of marsupial designed by this designer to bite one another on the face and for whom this designer designed a fatal, transmissible cancer which has put them on the verge of extinction being reduced to just 5% of their 1996 population when DFTD was first seen. And now this designer has apparently designed an entirely new cancer following the 'success' of this first one, and just at the point when trials of a vaccination were being completed.
Just a simple explanation of what on Earth this 'intelligent (sic) designer' is trying to achieve by this will do, please. If it wants to exterminate an earlier 'mistake' in designing this little marsupial carnivore surely it could have designed a more effective way to do it. Maybe it just enjoys experimenting with different cancers and watching creatures die of them?
Of course, the usual abandonment of the pretence that 'intelligent (sic) design' is a science with the resort to Bible literalism and the dogma that 'sin' is the cause of all suffering isn't open to them in this case. That excuse is normally and routinely trotted out when there are things like human viruses, antibiotic resistance and inherited genetic disorders in humans to explain away - it's all to do with humans choosing to reject God, apparently. However, this attempt to exterminate Tasmanian devils with nasty cancers doesn't seem to have anything to do with humans, either by cause or effect, but it still needs to be fitted into the 'intelligent (sic) design' paradigm if that is going to be claimed as a complete alternative to biological evolution.
I suspect everyone, including 'intelligent (sic) design' advocates, knows it can never do that and comes no where near offering a credible alternative to the well-established scientific theory of neo-Darwinian evolution by natural selection and genetic drift, as will be seen by the complete lack of intelligently designed answers to the questions posed by this finding.
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