Diabetes and enterovirus autoimmunity in glacial Europe

The incidence of insulin-dependent diabetes mellitus (IDDM), a chronic disease with a well-known genetic basis, is highest in Scandinavian and Sardinian populations. The high incidence of IDDM in Scandinavia and Sardinia, which were genetically isolated from the spread of agriculturists in Europe about 8000 years ago, suggests that an IDDM-susceptible genotype(s) may have been beneficial in Europe more than 8000 years ago. In glacial times, Europe had an extremely cold climate that was frequently interrupted by episodes of warming. When enteroviruses were locked in the ice and permafrost, glacial Europeans would have had little immunity to these viruses. Each time the climate warmed, enteroviruses would have spread through increased amounts of melt water. With a genetic ability to mount an autoimmune defense, the IDDM genotype(s) would have been beneficial in glacial Europe as a defense against all enteroviruses, including those that had co-evolved to mimic host tissue.