Perhaps their projecting jaws were less able to exercise and clear the eustachian tubes, as any modern child (or airplane passenger) discovers early. Add to thi

Perhaps their projecting jaws were less able to exercise and clear the eustachian tubes, as any modern child (or airplane passenger) discovers early. Add to this being by themselves on the European continent for a long while and reaching equilibrium with fewer sinus problems over time by adaptation. Then being attacked brutally by diseases from a new wave of settlement out of Africa. In North America some elapsed ~13,000 years was sufficient for the paleo population to be almost wholly destroyed by disease at first contact with Spanish explorers, by many accounts 90% dead by 1620.