GJB2 and deafness: We are left with the puzzling paradox of how the commonest GJB2 variant alleles causing severe to profound deafness: c.35delG, c.167delT, and c.235delC, have been measured at frequencies of between 1% and 4.4%, while measurements of reproductive fitness in deaf communities have been uniformly depressed [9–11, 18–22].