Thinking of Rome

 Reading Livy (but not in the original Latin, as former generations) I arrived to the mystery of the malaria in the gradual weakening of Rome and the Eastern populations in general. The disease appeared around 800 BC in Greece, and advanced westwards along the coastal swamps and wetlands. Possibly the climate was warming up too. 

Malaria is fatal for babies, and they found large cemeteries of babies in Italy, all dead in the same summer epidemy. The parasite evolved, the mosquito evolved and with them human populations, specifically thalassemia and sickle cell (the African variety but mutated independently in Greece too). 

Rome was founded in a swamp of the Tiber river, near the point where it could be traversed, hundred years before the arrival of the disease. When it arrived circa 100 BC, the number of children fell dramatically  (which now is attributed to infertility caused by lead in their wine and cooking in copper pots, although contemporaries attributed it to sheer unwillingness to marry and rear up children, not infertility.) and almost all senatorial families (clans) had disappeared by 100 BC. The lack of Romans  caused the collapse of the Republic when healthy "new immigrants" from the North understood the weakness of the ruling class. This narrative makes more sense than the battles lost and the strategic errors of war leaders.