However the connections are not at all random, but they observe certain strict symmetries. For instance, in each of the 3 "generations" of quarks and leptons,

However the connections are not at all random, but they observe certain strict symmetries. For instance, in each of the 3 "generations" of quarks and leptons, separately for particles and for antiparticles, all the different kinds of charges and spin sum to zero, e.g. for the 8 particles that are the 3 kinds of u quarks + the 3 kinds of d quarks + the electron + the electronic neutrino. Moreover, in a 3-dimensional space of the "color" charges and electric charge, the 8 particles and 8 antiparticles of a "generation" are located in all the corners of 2 cubes, not in arbitrary positions. So the set of elementary particles that we know is complete, there are no random locations where there could be extra particles. Any so-called "dark matter", if it would exist, would have to be something completely different and not related in any way with the known elementary particles.