An interesting article at http://thecostaricanews.com/ancient-cultures-and-prehistoric-in-casta-ri… the Costa Rica News reports on some archaeological discoveries in their country, on the slopes of volcanoes – presumably being very fertile locations for growing crops. At Turriable, the ruins of a city inhabited between 1500BC and 1400AD exist. It was abandoned over a century before the arrival of the Spanish. Another location on the shores of Lake Arenal – also close to a volcano – had a permanent settlement as early as 2000BC – but they also vanished around 1400AD. The article says that plague is suspected. At this point in time, of course, the Black Death raged across Europe, China, the Islamic empire, and impacted heavily on the politics of the world, more or less drawing a curtain across the Medieval period. Bubonic plague is thought to have been spread by rats – even in regions where rats were almost non-existent. If the same outbreak of plague occurred in the Americas a relook at Mike Baillie's book, New Light on the Black Death, Tempus: 2006, might be necessary. In chapter 4 page 57 'The Americas' he does in fact note abandoned towns and a sudden drop in population numbers took place in SW North America at this time. In his view the Black Death had an origin in a cosmic event – a comet, or cometary debris. This might explain why plague was common in so many parts of the world – but a word of caution. Recent research on the bodies of plague victims from European cemeteries have suggested Bubonic Plague was responsible.