The Mayan civilization flourished in Central America between the third and tenth centuries AD. Although isolated from other centres of mathematical activity, the Mayans achieved remarkable results in numeration and calendar construction. The Mayan numeration system, with 20 as base, was used mainly for calendar computations. Only three symbols were required: dots and bars, sometimes formed using pebbles and sticks, were used for 1 and 5, and a shell symbol stood for the numeral (but not the number) zero.
The Mayans had three kinds of calendar: a sacred calendar for religious rituals, a civil calendar based on the solar cycle, with 20 months of 18 days and 5 extra days, and a special calendar used for extended time-spans and employing a mixed-base numeration. George G Joseph, in his book The Crest of the Peacock, on the Non-European roots of mathematics, describes all these in some detail.
Mayan astronomy achieved a remarkable degree of accuracy, which is amazing considering that the Mayans never employed fractional quantities or decimals. The Mayan estimates of the length of a solar year and the duration of a lunar month were in excellent agreement with our current best estimates.
Catastrophic Droughts
All advanced societies require dependable water supplies as well as annual weather variations predictable enough to ensure a steady food supply. Climate changes can disrupt these supplies, to the point of collapse. The regular summer rainfall on the fertile land of the Yucatan Peninsula allowed the Mayan civilization to flourish for centuries. However, between 800 and 1000 AD, the civilisation went into serious decline, apparently as a consequence of sustained drought, and the population plummeted.
By the time of the Spanish conquest in 1520, the glorious days of the Mayans were far in the past. To understand what happened, we need a detailed historical rainfall record for the Yucatan region. In the absence of direct rainfall measurements, proxy data must be used.
There are two naturally-occurring isotopes of oxygen in rainfall water, O-18 and O-16. Their relative proportions vary with rainfall intensity. Heavy rainfall produced from cold high clouds contains a lower proportion of the heavier isotope O-18. This permits a reconstruction of the rainfall climatology from analysis of stalagmites, rock formations formed from the residue of rainwater dripping from cave ceilings.
Dr Medina-Elizalde and his team at the University of Massachusetts, Amherst have reconstructed the rainfall record of the Yucatan Peninsula over the past 1,500 years. Through mass spectrometric analyses of tiny stalagmite samples, they found that, during the period of decline of the Maya, the Yucatan Peninsula experienced a succession of drought events, with a 40% reduction in annual rainfall.
There are ineluctable similarities between the climate stress suffered by the ancient Maya and the weather anomalies we see today. A fuller understanding of past climate should help us to anticipate, and hopefully to prevent, threats to our society and ecosystem.
Sources
Martín Medina-Elizalde, 2023: Collapse of the Ancient Maya Civilisation: Aligning History with Geological Analysis. Scientia. Link
ThatsMaths 