The Selfish Gene - question

1. yes, it probably would

2. no the reason it would (possibly) work would be because the people most fertile at later ages, and so who are likely biologically "younger", would average the most offspring, and so genes that keep them younger longer would increase in frequency throughout the population.

so essentially it is purely theoretical? as in, because of the birth defect problem it would never be beneficial enough to be a real practical idea..

2. I understand that those genes keep them 'younger' in terms of fertility, but is there a proven correlation between fertility and living longer?

well the birth problems would only be an issue at first, after several generations they would become less common as those who are less likely to produce children with birth defects in later life will pass on their genes more. The initial increase in defects would obviously be a reason why people are unlikely to do it, but it is probably less of a factor than people not wanted to be told when they can breed.

I don't think there is no, but I guess the idea is that hypothetically an individual that stays youthful longer would also remain fertile longer, and such a system would select for such individuals. whether the hypothesis matches the reality I don't know. I guess this could easily be tested on rats

interesting! I imagined the population looking something like this '><' until those genes were the majority.. because as far as i know its something like after 40 its a 1/4 chance of birth defects of some sort...

so far i've found this idea in the book the most interesting part .. hopefully theres more like it later on

so far i've found this idea in the book the most interesting part .. hopefully theres more like it later on

well I don't think it is as high as 1 in 4, but it certainly is higher. interestingly the average age of women baring children is rising, so we might actually see an effect like this happening naturally! I found it a very interesting book, as was the Blind Watchmaker. I still need to read the Extended Phenotype, and maybe the God Delusion while I am at it

Think of it this way. If there were some genes that predisposed you to dying young, but you already had children before they struck, the genes are passed on to the next generation.

If you are not allowed to reproduce until these genes had had their effect, these genes could not be passed on, hence the next generations would be less likely to die young.

Rinse and repeat!

This is actually a very mainstream theory of senescence - age-related mortality is due to the accumulation of genes that have negative effects late in life but positive effects early in life (the "shadow of selection").



You're in for a treat. The book is packed with brilliance!

Average lifespan = (average age of death)/n

Therefore if you increase average age of death you increase average lifespan by simple arithmetic.

With regard to pleiotropic genes, the idea is that some genes might be beneficial when you are young (helping you to heal, or have children), but detrimental when old. They thus act to constrain life expectancy at birth, but are still selected. Artificial selection by preventing breeding until a certain age would counteract the early beneficial effects because everyone who breeds must have survived to that age. Thus their selective advantage will not be retained and future generations will not have so many, and so will live longer.

okay so when we assume that the average age of death would eventually would approach a certain number that could be considered the 'maximum biological age'

so with how much certainty can we assume that from this process,, this age could be extended to say, 150 .. ( for example) ?

Yeah, exactly. I would probably conceptualise it as an asymptote.

Who knows? After enough time, mutations could crop up that favour longer life - some animals are immortal so that is theoretically possible - and then we could preserve these mutations using artificial selection, thus increasing our asypmtote.

That is an interesting though: genes which compete with each other. Genes adapt themselves to get an advantage in terms of selection (mutations, genetic drift), so why genes shouldn't be in competition? perhaps humans came into being by competing genes, so apes evolved to humans step by step, because the human genes came out on top? but as far as I understand the meaning genes, which were defeated by the selfish genes, were not avalaible anymore, thus apes must not exist. But apes still exist...