 It is also worth noting, perhaps, that some of this ‘surplus’ structure corresponds to so-called ‘paraparticle’ statistics, or forms of quantum statistics that are neither bosonic nor fermionic. These were acknowledged as possible by Dirac as early as the 1930s but were only fully developed theoretically from the late 1950s. For a brief period in the mid-1960s it was thought that quarks might be paraparticles, before the same statistical behaviour came to be described in terms of the new intrinsic property of ‘colour’ leading to the development of quantum chromodynamics, which effectively pushed paraparticle theory into the theoretical twilight (for a summary of the history see French and Krause 2006, Ch. 3; for a discussion of paraparticles in the context of issues relating to particle indistinguishability, see Caulton and Butterfield 2012b). This suggests that paraparticle statistics can always be re-described in conventional terms – a suggestion that has been taken up by Baker et. al. in the context of algebraic QFT, thereby eliminating this form of surplus structure at least (Baker, Halvorson and Swanson 2015).