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Dr Who: The Lazarus Experiment - John C. Kirk — LiveJournal
May. 8th, 2007
01:00 am -
Dr Who: The Lazarus Experiment
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May 8th, 2007 01:19 pm (UTC)
I'm trying not to side-track the discussion too much, so I'll keep this short :)
>From this you get the conclusion that the most "successful" genes will cause
>their carrier organisms to be highly fertile and resistant to disease.
Not quite. The Selfish Gene says:
1 - genes exists to replicate (and replicate to exists)
2 - genes replicate via the mechanism of animals (plants, bacteria, slime moulds etc.)
3 - the most common genes are those that best help their animal pass on more copies of themselves
The latter means that the 'best' genes are those that best help their animal (i) survive within their ecological niche (or take over another one) and (ii) produce the most offspring *which in turn must survive to breed*.
This implies that diseases that occur after reproduction are irrelevant to evolution (although not the case with primate or other animals with significant levels of 'grandmother' infant care) and that high fertility is only required in situations of high infant mortality. Small numbers of well cared for offspring, whom in turn have an excellent chance of passing on their genes to their own offspring, are actually more valuable from the selfish genes' 'point of view' than large numbers of poorly/not cared for ones, many of whom die. Logically, the former strategy is aided by longer life spans and higher levels of intelligence. Cooperation between related individuals, group living, communication and the development of language also all help. Think pride of lions, troop of baboons or humans societies.
> However, there are limited resources, so you can't be too fertile
Efficient use of limited external resources isn't really an evolutionary issue per se, its effect is minimal unless an animals' breeding is so extreme that they use up all the resources in their niche before their offspring themselves can breed. The selfish gene isn't able to see the long term picture (please ignore my anthropomorphic terminology!), otherwise we'd not see the common cycle of 'boom-bust' in animal populations.
Dragging myself back to the point. I'm sure aging does have an evolutionary aspect, but I suspect that it's more a case of (i) how much internal energy/resources should be put into this individual breeding now vs living longer? and not (ii) when should this individual die off to allow their offspring access to its external resources?
As always, there are some special cases – spider mothers using their own bodies to feed their young, being one I can think of. In general though, the most powerful evolutionary forces are the simple ones – the ones that work directly on individuals and directly effect their breeding success.