I realise this is rather a late contribution to this debate, but here goes:

I am a health visitor practising in the UK and it has always seemed to me
entirely logical that a baby's outward abilities ( e.g. to reach out and grab
food and take it to his mouth) would keep pace with his inward abilities (i.e.
to produce appropriate enzymes for digestion of said food).  We don't decide
for our children the age at which they should start to crawl, walk etc. so why
should we decide for them when they are ready for solids?  (And by the way,
there's nothing remotely "solid" about the stuff most people feed their 4
month olds!)  What we DO do, though, is give our babies the OPPORTUNITY to
crawl by putting them on the floor to play.  If we were prepared to give them
the same opportunity to feed themselves - i.e. include them in our mealtimes
and put food within their reach - they would surely do it themselves from the
word go, accuracy increasing with practice.  If we were meant to feed our
babies with spoons we'd surely have evolved a spoon-shaped finger!

I think the idea of "feeding" babies (as opposed to letting them feed
themselves) is a bottle feeding thing - as anyone knows who's ever tried to
persuade a reluctant baby to take the breast or to feed actively when he just
wants to hold on!  Breastfeeding babies do the feeding - we simply offer them
the opportunity - so why suddenly change?

Gill Rapley, IBCLC, UK (new subscriber - thanks Jill!)