The problem for babies pre 4-6 months, is that the gut is still very open and porous at this age, and therefore food doesn't get fully digested the normal manner, but can leak into the blood system potentially causing infection at the time and intolerances and allergies later in life. And that usually means as an adult.
I am perfectly healthy...fighting fit in fact....but I do have several food intolerances. Most adults of our generation do....they often just don't know about them. I'm just lucky they they aren't all allergies, because they are possibly/probably/in part down to early weaning. I'm 38....and until I was 32 I could eat anything! Now I'm slightly gluten intolerant, I suffer IBS, and I bloat up like a Pufffer fish to smoked mackerel....and thats not all! I enjoy life...I eat well, I just know what suits and what doesn't!
And I know many many people that have developed both later life Type I or Type II diabetes....again, they were weaned early.
Its fine to make a decision based on your babies hunger and supposed needs, but I think it worth knowing the reasoning behind the recommendations too and why they have changed. Is a few more weeks really worth it?
I know many a mum who has claimed the 'it didn't used to be a problem' defense and chosen to early wean as they believe their baby to be ahead of the game. They probably are in desires and hunger but unlikely in terms of digestive capability....that deosn't tend to change much from one to the other.
Do you know back in the middle of this last century the doctors used to suggest having a cigarrete to help cure a cough or cold? Thank god for medical science, huh? We can't always stick with the supposed tried and tested!