May 20th, 2011, 04:29 PM
When a somatic cell turns into a cancerous one, it shows a much higher rate of telomerase activity in turn keeping the integrity of telomeres making the it immortal whereas normal cells telomeres shorten as they divide and senesce.
How does evolution account for this "advantage" that cancer gives to a cell making it immortal, why can't all cells become cancerous to live forever. Is this a possible route for evolution ?
May 22nd, 2011, 01:31 AM
The lack of telemorase activity in most regions of your body is to reduce the odds of them developing cancer; if a cell starts to reproduce uncontrollably the telomeres will shrink with each generation until they all die, preventing devastating consequences.Originally Posted by Dkav
For cancer to actually develop they need increased telemerase activity.
You had cause and effect mixed up.
In labs animals that were given elevated levels of telemerase had reduced lifespans due to the high incidents of cancer.
The best potential thing would be greatly increasing other checks on cancer to allow for higher telemerase levels.
In germline stem cells telomerase is still active.
There is no advantage for a cell to become immortal. Our growth and development requires cells to senesce while others to grow. Even now, our bodies are regularly killing off old cells and growing new ones.
You also need to look at the economy of energy within the organism. An immortal cell will be a serious drain on the organism's reserves. The only way to compensate will be to increase the metabolism. This is also disadvantageous as it will require the organism to expose itself to more danger while it searches for food.
Finally, there is also no advantage in having a high number of immortal organisms. Can you say, 'inbreeding'?
May 22nd, 2011, 01:20 PM
How can a species evolve if it's members are immortal? Inevitably they become unfit as the environment changes or they are out-competed by organisms which continue to adapt by reproduction and death.
May 22nd, 2011, 05:18 PM
I was thinking that evolutions effects are greatest on the individual level and immortality would be the ultimate show of fitness following by a fixation of that trait in a population. They can evolve until they run out of room I guess.How can a species evolve if it's members are immortal? Inevitably they become unfit as the environment changes or they are out-competed by organisms which continue to adapt by reproduction and death.
May 22nd, 2011, 05:49 PM
But individuals, immortal or otherwise, don't evolve. Their genomes are largely static over time. The variations that do occur are never expressed across the whole organism and are, in any case, usually detrimental. A population of organisms in which immortality is an inheritable trait is going to become increasingly uncompetitive versus mortal organisms over time. Or at least the immortal portion of the population will. They'll be out-competed by other species or even just by the mortal portion of their own breeding population. It's not an evolutionarily beneficial trait.I was thinking that evolutions effects are greatest on the individual level and immortality would be the ultimate show of fitness following by a fixation of that trait in a population. They can evolve until they run out of room I guess.How can a species evolve if it's members are immortal? Inevitably they become unfit as the environment changes or they are out-competed by organisms which continue to adapt by reproduction and death.
I would like to add on to what TheBiologista was saying by adding that with biological immortality it is likely that, due to the costs of reproduction, the species would then quickly evolve to reproduce much less often.
Note that, due to relatively lower adult mortality rates due to causes like failure to survive winter there would be less room for young animals to fit in, increasing competition from more experienced, larger, animals. I don't know that much about herbivores, but in carnivores (as in, Carnivora) the young, once they leave their mother, have a very hard time trying to survive and fit in for the first few years.
Low profitability of rearing young combined with increased importance of maintaining the life and health of the individual organism -> greatly reduced reproductive rates -> greatly reduced ability to survive changes in the environment (climatic, competing species, adjacent members of the food chain, etc).
Predator prey dynamics would be interesting. Without the weak to prey on (old, sick, and young) I would imagine predator populations would initially plummet, although the starving would soon be suitable prey.
It would be an evolutionary dead end, like asexual reproduction, only much harder to evolve.
Obligatory asexual reproduction is evolved regularly in the animal kingdom, but with the exception of the rotifers, the species then quickly die out and fail to diversify.
Had I thought of this I would have mentioned it in my first post, but that would likely be the explanation behind the limited lifespans of animals.
I wonder what exactly the evolutionary pressures behind longevity are-why is it beneficial for Greenland sharks to survive 200 years?
I do know that ability to level of predation a species experiences is correlated with lifespan (regardless of whether or not that predation is their, such as even in a captive setting).
There's one possible set of selective pressures that might select for immortality- a highly hostile environment wherein death by violence, pathogens or environmental hazards is so common that no death due to sensence (aging) can be tolerated. The turnover of individuals might then be sufficient to allow evolution to progress without the problems I mentioned previously. Hard to say whether this is possible in practice.
I'll be recommending your account be banned for spamming.Yes, stem cell is seen as the best futuristic medicine to cure most of the dreadful ailments. I feel this will be the next best medicine on the earth.
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This might apply to amoebas or other microbes that seem not to age. Alternatively, immortality might be adaptive off-planet, where the constraints of geography don't apply and generational turnover would not be an issue.
I wouldn't call it adaptive, but it might remove a selective pressure against immortality.
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