For years I wondered what it was about marble that could convey such softness. Look at this baby, sculpted by Antonio Tantardini, for example:
Pietro Bernini was an Italian sculptor who lived during the Renaissance. This detail of one of his sculptures is an exceptional example of the ability to capture weight, volume and fleshiness in a piece of marble.
I've since formed a theory about this. This kind of scupting is so slow, that it gives the artisan a lot of time to think through his/her creation. Maybe I'm wrong here - and I am sure there are many other factors involved, not the least of which is skill - but the constraints of the medium must play a factor.
This was brought home to me about two years ago when a sculptor friend of mine, Anne Dean, was having trouble finishing a work in time for a show and asked me (and the three others in my little art group) to come help her do the finishing.
(This is one of Anne's pieces, not the one we worked on)