Quite some years ago (probably in late seventies or early eighties), we had a mom who happened to be an RN attend our LLL meeting; she always came
armed with a book on child development to check on our information. She told us that research "proved" that babies HAD to be given solids by six
months or would not develop chewing skills. Yes, there WAS a study
cited, but when the RPA (Registered Physician's Assistant) at my
pediatrician's office looked it up, we found out that the study did not
involve full term healthy infants; rather, these were babies who had
other medical or neurological problems (I believe it was babies with a
particular problem, not sick babies in general). And yet the study was being used to prove an absolute cut off for introduction of solids. Sorry
I don't have more info about  the exact study, but it's in there! (old
medical research...)
Pearl Shifer, IBCLC
ancient LLL Leader since 1981 and still involved!