> >
> > it is wrong to view individuals that do not breed as making no
> > contribution to the perpetuation of the genes they carry. You do not
> > need to perpetuate genes through your children - you share on average
> > the same percentage of genes with your children as you do with your
> > siblings, so if you do not breed yourself but nonetheless contribute to
> > the survival of the children of your brothers or sisters, you have
> > 'perpetuated your genes' . . . This is the basic reason why the
> > demographic shift doesn't have to contradict standard Neo-Darwinian
> > reasoning.
>
> I don't see how this fixes things, Eric. If upper income people have
> smaller families on average, then they also have fewer siblings on average
> and those siblings themselves have smaller familes, cet par. And the
> reverse is also true: the poor not only have larger families, but also
> more siblings with larger families. If anything, this line of reasoning
> seems to multiply the power of DD's objection.
>
I never made the argument you attribute to me here. What I actually wrote in full was:
> Again, comparatively very few people in a position to mate forgo having
> children entirely. However, it is wrong to view individuals that do not
> breed as making no contribution to the perpetuation of the genes they
> carry. You do not need to perpetuate genes through your children - you
> share on average the same percentage of genes with your children as you
> do with your siblings, so if you do not breed yourself but nonetheless
> contribute to the survival of the children of your brothers or sisters,
> you have 'perpetuated your genes' (I don't like this kind of language
> but use it because it is widely known, if also widely misunderstood). In
> terms of shared genes your niece is worth as much as your grandchild.
>
> It's worth remembering that maximizing the number of children you have
> isn't necessarily the best way to 'spread your genes' (it is probably
> better to think of maximizing the number of grandchildren you have ...)
> This is the basic reason why the demographic shift doesn't have to
> contradict standard Neo-Darwinian reasoning.
>
The first paragraph was intended to deal with the point raised by DD that what we might call 'selfish gene theory' cannot apply to people who do not have children AT ALL, EVER, i.e. those who die without leaving any direct descendants. (I referred specifically to 'individuals that do not breed'). However, as I explained, the theory does cover such people. Let's say X dies childless drowning while saving his niece. If his niece survives to breed, X has still perpetuated 'his' genes.
The second paragraph (which refers to people that do breed) was merely intended to point out that in evolutionary terms children are no use if they don't survive to breed themselves. Relatedly, as the demographic shift has taken place over only a couple of generations, you cannot view it as contradicting the selfish gene theory - these things have to work themselves out _in evolutionary time_. You can say that people on higher incomes are still trying to maximize the number of descendants they leave, but although they have higher incomes their children are also in a sense more expensive, and they thus (apparently paradoxically) have smaller families. Does this mean their genes decrease in frequency in the gene pool? Not necessarily. For example, historically it seems that wealthy males tended to leave plenty of bastards in their wake, and they probably still do so now.
Untidily, I shall leave this here as I have to go look after my daughter ... and thus perpetuate my genes ...