Ok, it's in Wikipedia! But, backbone's are normally singular and control a single organism. I think that the metaphore held fine until 1995, but that which has

Ok, it's in Wikipedia! But, backbone's are normally singular and control a single organism. I think that the metaphore held fine until 1995, but that which has come since then does not look, act or smell like a backbone to me... (see what I did there with the metaphore thing :))