twiglett - I just meant a 2 year old is pretty helpless regarding needing nappies, limited speech, constant supervison and so on. I do agree though that they are toddlers not babies, my dd is VERY grown up, more so than her brother but maybe that's girls for you Bit confused as you said originally past 12 months, then you said a 2 year old so that is actually a whole year older??
Still not sure about using the walking/talking/pulling criteria. Lets face it kids can walk at under a year but they are hardly grown up, also with pulling, well yes babies can pull things like things off the table, your purse out your bag etc.. all pretty much as yet unconstructive and very limited in independence. So when looking at these 'cut off' points they don't actually make any sense... so I guess it does all come down to a funny sort of belly button feeling.
Personally I think its down to what one feels as being a separation between your body and your childs and in this society (in the majority) we just feel that this separation should be way lower than in others. I actually find it odd that some people stop breastfeeding at 6 months for example to have this 'separation' but then spend most of the time holding their babies and wiping their bottoms/faces etc... we do all of this till they are toilet trained which is anywhere between 2 and 4ish... which seems like a good time to stop breastfeeding!
Incidentally K Dettwyler has argued that in some societies the onset of adult teeth is a time for stopping breastfeeding, ie between 5-7. I guess this why the first set are called 'milk teeth'.