The only other thing I am going to say on the matter, is that the WHO/UNICEF information on the subject of weaning states:
"Health experts agree that around six months is the best age for introducing solids. Before this, your baby?s digestive system is still developing and weaning too soon may increase the risk of infections and allergies. Weaning is also easier at six months. If your baby seems hungrier at any time before six months, they may be having a growth spurt, and extra breast or formula milk will be enough to meet their needs."
I would like to highlight the use of the word may.
Nowhere in an hour's search on the internet on NHS websites (which incidentally have lots of out of date info, so many people can be forgiven for having the wrong idea, and may explain why there is so much ambiguity on the matter), the WHO site, UNICEF and many other websites does it emphasise (with the same degree of importance as is implied on mumsnet and other more anecdotal websites) the apparent dangers of introducing non-milk foods between 4 and 6 months.
Also I cannot find a single reference to a peer-reviewed scientific article on the matter, other than one minor reference to a Canadian study of 14,000 infants that showed that levels of allergies and food intolerances are not related to length of time spent breastfeeding.
Like I said - if you can refer me directly to these I will be very grateful!
I don't mean to play devil's advocate in all this, but without substantiated evidence (which nobody has referred, just quoted sites like netmums, and referred generally to NHS and WHO guidelines which are no more specific) people being evangelical about not weaning until 6 months (and by doing so emotionally blackmailing for whatever reason those that can't or don't wait until 6 months) are as bad as the old wives that started this in the first place.
Also, I take all official guidance (and it is guidance, it isn't law) with a pinch of salt, due to its changing nature, and its tendency to dumb everything down (e.g. what you can and can't eat during pregnancy, in particular alcohol).
To finish, all I'm going to say is what I said before: Use common sense, and listen to your child, don't use what I've written above as an excuse to start early weaning if it's non appropriate. And if you have a child that is prepared to wait until 6 months, be grateful.