"Because it's not just the milk - it's the fact that the mother is clearly very dedicated to her child to do it, they can usually afford to take time off work, tend to be better educated, will be with their child more than someone bottle feeding potentially - all these things have a positive effect on the child, but it's not the breastmilk which does it."
Why aremost people happy to accept that fish oils given to children who are hyperactive can improve cognitive ability in tests, and behaviour, but not prepared to accept that the fats in breastmilk - which are completely different from the fats in formula - and are given to an infant during the period of fastest growth - might have some impact on cognitive ability?
Why is the view that 'you are what you eat' so acceptable in relation to nutrition EXCEPT when it comes to the sole food of infants? Breast milk and formula are not the same. Why are they expected to have the same effect on the growing body and brain of a child?
"they can usually afford to take time off work, tend to be better educated"
Actually all mothers in the UK get six months maternity leave, and almost all mothers take this. Most women who are still breastfeeding at six months can return to work full time and still continue to breastfeed, as babies are generally on solids by this point and often only breastfeeding a few times in a 24 hour period. In any case, evidence is that women who are most likely to breastfeed in the short, medium and long term are also those women who are most likely to return to work after maternity leave.
And yes, you are right, mothers who breastfeed do tend to be more intelligent than women who don't breastfeed (don't throw rocks at me - this is something that has been thrown up by research), and their children may well inherit this, but even when IQ, education and family income has been controlled for, children who have had long term breastfeeding still appear to gain in IQ over children who have had little or no breastfeeding.
Chunderella - I agree that our diet these days is very far from the diet we have eaten for the bulk of human history. Some people think this is partly responsible for the explosion of cancer, obesity and other horrible diseases that human kind now suffer from ever increasing numbers. Cows (from whose milk formula is made) are largely grain fed now, and of course this is profoundly unnatural and results in them experience higher rates of disease.