There are few directly observable effects of this sign reversal, but it is nevertheless a bizarre and counter-intuitive result. We have no idea where these half integer spins come from or why most fundamental particles have them, yet they do. Our world is made of particles, some with half integer spins and others with integer spins. Quarks and leptons, plus composite particles like protons, neutrons, and many nuclei and atoms all have half-integer spins. The integer spin particles are called bosons because the statistics of their behavior in groups is governed by Bose-Einstein statistics, as first described by S. N. Bose and Albert Einstein.
Fermions are highly territorial individualists.
If one fermion is in a particular quantum state, then all other fermions are excluded from that state, resulting in the Pauli exclusion principle. In a universe where electrons were bosons rather than fermions, no life would be there to worry about it. We owe our very existence to the Fermi-Dirac statistics of electrons. Bosons, on the other hand, are gregarious groupies. The more bosons that pile into the state, the stronger becomes the tendency for others to join them.