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EDIT: As it turns out the method I had thought of using to combat aging doesn't work the way I expected. As such I have rethought this question in more vague terms.

New Question: Using current hypothetical methods of radical life extension as a basis, in what manner would age manifest in a human's appearance?

Original Question

In my setting, telomere replacement therapy effectively eliminates a lot of the ageing process. However, to my knowledge this would only affect the DNA itself reducing the onset of things like cancers.

Is there any knowledge as to which aspects of ageing this would affect?

Would people still have saggy skin or get shorter?

How do we decay when our telomeres don't?

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This question asks for hard science. All answers to this question should be backed up by equations, empirical evidence, scientific papers, other citations, etc. Answers that do not satisfy this requirement might be removed. See the tag description for more information.

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    $\begingroup$ People get shorter because of gravity imposing itself over time on (principally) cartilege. You can improve the cartilege to slow the process, but they'd still shrink. Saggy skin happens when fats disappear, often due to the appitite change that comes with a slowing metabolism. But, you'll see saggy skin on people of any age who lose a lot of weight rapidly. Frankly, neither is due only to aging. Also, many chemicals can help to make the aged look young. In your world, is not aging anything more than parts not wearing out? $\endgroup$ – JBH Dec 24 '17 at 19:51
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    $\begingroup$ Douglas, what you did was ask a new question. You should roll back this question to its first version, and then post your new question as a new question. You have invalidated Will's answer below, which is something we do not want to do. $\endgroup$ – kingledion Dec 24 '17 at 20:48
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    $\begingroup$ suggest changing hard-science to science-based. I don't feel like searching journals today. <grin> $\endgroup$ – Sherwood Botsford Dec 26 '17 at 19:29
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With non decaying telomeres you would still get cancer. You would get more cancer.

http://learn.genetics.utah.edu/content/basics/telomeres/

Cells normally can divide only about 50 to 70 times, with telomeres getting progressively shorter until the cells become senescent or die.

As a cell begins to become cancerous, it divides more often, and its telomeres become very short. If its telomeres get too short, the cell may die. Often times, these cells escape death by making more telomerase enzyme, which prevents the telomeres from getting even shorter.

Telomeres are a cancer defense. A cell only gets so many divisions and that number is governed by the telomeres. That is usually more than the cell needs to do its normal job. If the cell mutates into a cancer it will divide like mad as it has uncontrolled growth. It will quickly use up all its allotted divisions. The telomere runs out and the cancer cell dies. Who knows how many cancers die on their own because this emergency self-destruct mechanism is built in?

The only way around this is if the cancer (by luck) mutates the telomerase gene which is only supposed to be used by stem cells and certain other cells. It can elongate its telomeres so they do not run out.

So: your people with non decaying telomeres would do well with diseases where cell senescence is the root problem - dementia, maybe? But they might not escape cancers long enough to develop dementia.

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    $\begingroup$ In light of this, I think I'm going to have to completely rephrase the question... $\endgroup$ – Douglas Dec 24 '17 at 18:20
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    $\begingroup$ This was most helpful. $\endgroup$ – Douglas Dec 24 '17 at 18:20
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    $\begingroup$ This is not entirely accurate. Cancer cells indeed activate telomerase and keep dividing indefinitely. However, this mutation is more likely to happen when telomeres are short. Studies on mice suggest that telomerase-deficiency (resulting in shortening of telomeres) leads to higher cancer risks. Therefore, it is quite likely that keeping telomeres long will work as cancer prevention as well as ageing prevention. $\endgroup$ – Olga Dec 24 '17 at 21:19
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    $\begingroup$ @Olga - the research article is not freely available but the accompanying editorial is. nature.com/articles/35020662. The mice studied were constitutively cancer prone p53 mutants. Also, mice have different (longer) telomeres than humans and telomerase deficiency does not cause normal mice trouble. It made these cancer prone mice have more cancer. Not clear to me how these double mutant mice are relevant to humans with constitutively active telomerase. $\endgroup$ – Willk Dec 25 '17 at 2:41
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    $\begingroup$ @Will, mice lacking p53 provide a better illustration of (and make it easier to study) cells with short telomeres. As research shows, these cells are more prone to mutations, including cancer. Long telomeres preserve the chromosomes integrity and prevent their fusion or damage. In healthy humans, telomerase is active only in fetal tissues and adult germ cells. In somatic cells, this activity is low or non-existent. Therefore telomeres become shorter with each division. But as they shorten, the risk $\endgroup$ – Olga Dec 25 '17 at 3:59
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There are many different approaches to combat ageing. Wikipedia is a good place to start learning about them.

Assumptions

If we are successful, humans theoretically will achieve biological immortality or near immortality. Specifics of how it can be done are outside of the scope of this question. So, let's just assume that people do not age anymore and stay in their peak physical form. However, they still can die:

  • murder and suicide are possible;
  • lethal poisoning by radiation, fast-acting poisons, etc. is possible;
  • starvation will lead to death;
  • auto-immune diseases and infections like Spanish flu will have higher fatality rates due to higher immune response.

Signs of age

Most of the effects of ageing will be psychological. Despite no signs of biological ageing (everyone looks young), older people will demonstrate more mature and conservative behaviour. It is important to note, though, that psychological development and maturation of non-ageing and long-lived/immortal humans will be different from ours. I will not be surprised if more stages appear, something like early middle adulthood and mid-adulthood.

When it comes to appearances, older people might prefer hair and clothing styles similar to their youth (but not necessarily wear them). They might also tend to dress 'age-appropriately'. Most of them will, probably, keep the same music and food preferences as in their youth (however, immortality might change neurological processes responsible for our preferences).

I would also suspect that older people will use slightly different language patterns. Their speech will include more archaisms. It is also quite possible that their social interactions will adhere to earlier norms (think about differences between you and your parents when it comes to social situations).

I also believe that humanity will experience a dramatic change in culture and society once ageing is defeated. Unfortunately, we can only speculate about its outcomes since there is no true frame of reference for immortality or permanent youth.


slow-acting poisons are most likely will be ineffective since boosted regeneration and immune response are required to stop ageing

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Teeth, you still only get one set of adult teeth, so your teeth will be a sign of age. Enamel cannot be regenerated as it is acellular https://www.sciencedirect.com/topics/medicine-and-dentistry/amelogenesis

Many parts of the eye (lens, vitreous humor, ect) are still one off things that can't repair themselves so eyesight will still deteriorate. Although there has been some success in regenerating the lens but only if the lens is removed first, https://www.nature.com/articles/nature17181

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    $\begingroup$ Dentin can regenerate. It also seems that many parts of the eye can also be regenerated. I think that when we stop ageing we will be able to regenerate any tissue. $\endgroup$ – Olga Dec 25 '17 at 3:04
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    $\begingroup$ dentine can enamel can't, nor does it help you replace teeth once they wear out. dentine is acellular if it wasn't it would be a huge infection risk. Many parts is not the same as all parts, several parts of the body never evolved even the pathways for regeneration, there was no need they last long enough for a normal lifetime. $\endgroup$ – John Dec 25 '17 at 5:14

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