Say, unrealistically…but just say, that an entire population is gripped with ‘longetivity mania’ or whatever you might call it. The idea of lengthening lifespan combined with ‘vigor’ is all important. How this happens is just details…whether runaway sexual selection takes place with emphasis on age combined with vigor or the population decides no babies until you are 40…does this for a few generations then says no babies until you are 45…go on a few generations etc etc.
I don’t think the genes that are responsible for prolonging the length of time a person is fertile have anything to do with how long someone lives. Especially when you figure in the fact that it’s mostly women that get infertile. Men are more likely to keep making sperm in their later years. They might make less, and they might be less mobile, but they are still there, and theoretically capable of getting a woman pregant. After menopause, a woman can’t get pregnant at all.
When a person dies is determined by…well…I’m not quite sure. I know there are these things called “telomeres” on the end of DNA strands that help protect them. As we age, these telomeres shorten and out DNA is more prone to damage and improper replicating. So I guess you have to find the genes that are responsible for the length of these telomeres and breed people that have them.
Or just breed people with old relatives. I have a great aunt who’s 102, my grandfather died at 90, and I had two great uncles who were over 90! I offer myself up for breeding.
In my own amateur estimation, not by much. Natural selection has pretty much already done that for us. Aging represents an accumulated damage process caused primarily by cellular wear and tear from the metabolism of food and oxygen (prevailing theory, not conclusively demonstrated). If this effect were mitigated, my best (again, amateur) guess would be that the average human lifespan would be roughly 110 years with a very small standard deviation—perhaps 5 years, 10 at the most.
Robert Heinlein, in his Future History timeline, created an organization called the Howard Families (after millionaire Ira Howard, who founded and endowed it), for the purpose of lengthening human lifespan. IIRC, the criteria to be a member were that all certain recent ancestors (great-grandparents, I think) had to have lived past a certain age, though I don’t remember the exact details. I’d think that would be a first step, assuming that aging is influenced by genetics (the length of your telomeres, for example).
This is going to be from memory, but I recall an article in the Guiness Book of World Records on the oldest humans. When it came to verifying the actual ages of the very old Guiness seemed to set a limit of around 116 to 120 years of age.
That area may be the maximum limit if such a limit is indeed programmed in our genes.
The problem is that you don’t find out who’s long-lived until well after they’re past the point where they can breed. For a similar reason, there’s no selection pressure against diseases that don’t manifest until old age.
That’s why I said no kids till 40 for a few generations…then 45 etc.
I am not a biologist…but I find it hard to believe that there is a lifespan limit at 120. Once you select for it, I would think that a few hundred years could be possible…though it would take many generations to get there.
Of course, I am not a Biologist…hence the question
…or you could let anybody breed, but the rule is if you die before 80, they kill all your descendants. That would create the appropriate evolutionary pressure.
It isn’t just increasing life span…but slowing the aging. Not that people routinely live to 120 but are elderly at 70…but live to 180 and still having kids at 100…
But the point is getting better genes! Looking at all the problems evolution has found solutions for in the past, I can’t see why we shouldn’t be able to evolve to get aribtrarily long lifespans if we went for it. The reason we don’t get very old now is that there hasn’t been any use for it - even the fact that we’re able to get old enough to be grandparents (at which point or offspring obviously can care for themselves) seem to me to be a bit of sheer luck. However, I think I’ve read somewhere (Dawkins?) that the curious thing isn’t that we age, but that we don’t age faster, so I suppose there’s a whole lot of problems to overcome, and evolution towards superseniority might be a slow one.
Not that Nachiketas would care: O Death, these are fleeting; they weaken the vigour of all the senses in man. Even the longest life is short. Keep thou thy chariots, dance and music.
Heinlein’s Howard families, as mentioned upthread, were started by Ira Howard, a bachelor who died without children. His trustees searched for people of breeding age, who had four living grandparents. In the latter 19th century that was quite a feat. Later you could qualify as an “undiscovered Howard” if you furnished proof of four grandparents all living to the age of 100.
Delaying reproduction causes longer lifespans as species which produce fast tend to die young. I expect humans spans to naturally get longer as we are already selectively breeding ourselves to reproduce at later ages and having fewer children. Eventually we will bump up against a limit, but theoretically, the longer we delay reproduction, the longer we will live as our bodies will find a way to adjust.
Researching on ‘Senescence’ will tell you more what you wish to know.
Here’s a pretty interesting and relevant source. The chapter I read said that experiments done using the OP’s method, taking eggs and creating new generations from older and older specimens, increased average life span from 33 to 43 days in females and 39 to 44 days in males. The book also goes into what the actual mechanism for a genetic basis of age is. Levels of antioxidants seems to be a major factor. A study was done to compare Drosophila that varied by chromosome. The chromosome that accounted for 2/3 of the lifespan also contained genes that code for antioxidant enzymes. Another study showed that longer living Drosophila were expressing more of the antioxidant-coding genes. One more study involved transgenic drosophila, with extra copies of the antioxidant-encoding genes. From this cite, [warning: powerpoint] the flies lived about 30% longer, and functioned better in old age. So it looks like selective breeding and genetic engineering have longevity results, but don’t expect to see 300 year old people any time soon.
I vaguely remember seeing a documentary about a man who was trying to reduce his intake of oxidizing agents by only eating a few hundred calories of fresh fruits and vegetables a day. If I recall correctly, some parts of his body, like blood vessels, aged very well, but others, like his skeletal structure, were decaying rapidly. It will be interesting to see how long he lives for.
This is patently false. In fact, having children later in life (for women) is known to significantly increase risk of congenital abnormalities and miscarriage. Cite, note the doctor’s quote under the heading “This ‘time clock is real’”
As to the OP’s question, I am not aware of any evidence that there is a gene responsible for lifespan. Perhaps you could say a person with few genes related to chronic conditions is likely to live longer, but a single “lifespan” gene? I doubt it. If you know of such evidence though, feel free to provide it.
That would probably help; longevity tends to run in families.
Quite possibly true. We live about 3 times as long as other animals with our metabolic rates generally do already. We could probably produce a population where the majority live longer than the majority of people in the normal population do though I expect.
Socially it doesn’t strike me as a particularly good idea to have a society top heavy with “vigorous” old people. Vigorous old people are still old people with their attendant physical compromises, and there’s a limit to how many older people society can support and still be economically competitive.
I just wanted to bring up this news from a few years ago about John Sperling investing in longevity research. It’s particularly coincidental because the Sperlings were a fairly major family in Heinlein’s Howard Families.
