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A few years back when I was reading The Selfish Gene by Richard Dawkins, there's this short passage where he theorizes about a way to achieve an increased lifespan through controlled evolution.

The theory goes like this: we don't tend to have medical problems until after 30 because we all tend to reproduce before that age. Thus, people who tended to die before 30 never passed on their dying-prone genes.

So, if you didn't let people reproduce before a age X (where X starts at 30) and then slowly move that age up, you could use evolution to increase lifespan.

The ethical issues notwithstanding, is there any reason why this wouldn't work? If it would work, how long do you think you would need to sit at each value of X? How far apart do you think each value could be? Finally, how many generations, using this technique, would it take before someone would live to be 1000 naturally?

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The well quantifiable subject of say e.coli evolution is a totally different matter than say human evolution on aging, no less. This subject in the way it is phrased may be better suited for skeptics.SE (which is meant to discuss the information provided by notable sources). –  Lo Sauer Oct 3 '12 at 8:44
@LoSauer I see no great difference between E. coli and human evolution. They same forces drive both of them. Granted the human genome is orders of magnitude more complex than that of E. coli but nevertheless, the governing principles of evolution are the same in both cases. –  terdon Oct 3 '12 at 14:04
@terdon bacteria have a lot more lateral gene transfer and can acquire plasmids to add new chromosomal material. They also have co-regulation through operons. Prokaryotic and eukaryotic selection and evolution are remarkably different, at least to the level of mechanisms described in this question. –  shigeta Oct 3 '12 at 15:56
All true @shigeta, I am just saying that the driving force of selection still depends on the time that an individual reproduces, whatever way it does so, be it sexual or budding or whatever. In any case, this is a discussion I would love to have over a beer some time but not really appropriate for the comments of the poor OP's question. Unfortunately. Maybe we can continue it in chat at some point? –  terdon Oct 3 '12 at 16:07
@terdon wish we could get a beer. not only would the conversation be welcome, but that could mean I was in France! Its been a while :) –  shigeta Oct 4 '12 at 4:14

1 Answer 1

up vote 7 down vote accepted

I think this would probably work. The grandmother effect, which is one of the main theories for human longevity after fertility might indicate that human lifespan would increase if the children come later.

Just have to disclaim here: We will never do this. Many unthinkable consequences would result...

If you simply forbid anyone to have children before they are 40 or 45 (fertility doesn't drop until age 35 or so), forbid invitro fertilization and medical assistance to conception we would probably be looking at a prolonged lifespan. Infertility rates in women at age 40 are not clear, but one estimate is that 40% of women can have children at 40 years of age. If we want to seen an effect early, we would push the age up a year or two. Forbidding in vitro fertilization and other medical assistance to offspring we could look like a 80-90% cut of people - lots of people would never have children. This might make people unhappy an destabilize the social fabric.

Its not clear how long this would take. The generation time would go to 40 years from about 20 now - 40 to get to childbearing age, but results would take 80 years - when we find out how the children would fare. Given the C elegans longevity experiments and the fact that we are starting with 8 billion people, we probably would find some great late age breeders who may also live long. But for the longevity phenotype to set in it would take several generations as we are looking for an indirect effect: later breeding causing longevity. The Belyaev experiments which produced domesticated foxes by strong selective breeding took some 30ish generations to complete though they saw a significant effect in just 10. It could take a similar numbers of selection rounds in this cse. 4-500 years. Ethical issues aside, this is why most geneticists study flies.

There would also be a lot of other negative socioeconomic consequences to this thought experiment. One good thing is that the population of the earth would plummet - many people would be eliminated from the gene pool, though eldercare would be a major part of the world workforce. Lots of work, not clear who is going to pay for it, but low unemployment and low low wages may result.

Why do I feel like this guy? So you see Mister President, this is quite a distinct possibility, though some sacrifices would have to be made.

The science of human eugenics is not scientifically wrong, but selective animal breeding and lab experiments don't usually evaluate or care about the consequences of large peturbations in the gene pool.

You would also have a lot more autism and Downs syndrome and other congenital defects which tend to show up in offspring of older parents. These issues might improve with application of biotechnology which screens weak sperm and eggs without ruining the effect you are looking for, maybe not.

Since we are selecting against fecundity, the human race could be dogged by fertility problems or chronic genetic diseases which the genetic contribution of some of the more robust people in the gene pool being removed and the tendency to such age-related birth defects might not go away given the drastic selection pressure we are putting on the gene pool.

Other consequences you might not expect; some physical traits associated with longevity and prolonged fertility would cause us to look more alike and not necessarily in a good way. Browse the internet; its probable that we would get shorter and possibly uglier?

There are many more direct ways to increase the human lifespan - better diet, exercise, the elimination of poverty, vaccinations, proper medical care, access to clean drinking water and a lower birth rate (fewer children not later) all are known to directly effect longevity, having more than doubled the human life expectancy in the past few hundred years.

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What a great answer. +1 –  LanceLafontaine Oct 3 '12 at 15:14
A potential side effect of the selection would be a substantial delay of the age of puberty, as to, say, 30, which would effectively extend childhood. Longer lives are usually correlated with later age of sexual maturation. –  mgkrebbs Oct 3 '12 at 18:36
@mgkrebbs yup this is one possible part of an outcome. All of this can be imagined when one looks at what happens to domesticated foxes - they became more juvenille in appearance when they were genetically tame. would all people also start to look older when they are younger? not sure, but stimulating to think about. –  shigeta Oct 3 '12 at 20:36
@LanceLafontaine thanks dude! –  shigeta Oct 4 '12 at 4:15

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