Like Ryn's DS, both my boys could hold their heads up from birth so that's probably not a good sign, not on it's own anyway. When Jack was a baby, a paediatric dietician told me the signs that a baby is ready for solids are losing the tongue thrust reflex, getting teeth and showing an interest in food. The 3rd one on its own isn't enough as they will usually be interested in it before being ready for it. This makes more sense to me than a set day based on age, same as Ryn said. But I think the guidelines say 6 months as at that age most bubs are ready and that way people are less likely to misread the signs and start early. I will also say that the teething one is interesting - Jack got his first tooth at 6 months but was not interested in eating for months after that. Tom got his first 2 teeth together at 5 months and when I started him on solids at 6 months, he really loved them and was a good eater.

I think if we still lived in a society that trusted our maternal instincts, there would be no need for an age guideline at all.

Erin, good on you for taking the time to reasearch. How interesting that you couldn't find anything. I checked out the LRC and you have to subscribe or pay a one off fee for articles so maybe these studies have to be paid for?