Removal of forests for slope-land agriculture also destroyed habitats of many terrestrial fauna that were part of the Maya diet, including deer that were likely decimated in large numbers during the Late Classic times. This was exacerbated by the fact that deer are not particularly abundant in tropical forests in the first place. It is suspected that the Maya occupying the forested (or not) Lowlands found it progressively difficult to source protein in their diet (Sharer, 1994).
Thus, they turned their focus on domesticated grains. The maize-based diet that they were so dependent on was rich in calories but lacked in other important nutrients. Although it was supplemented by beans, squash, tropical fruits etc, it was not a well-balanced one that included all nutrients and important amino acids that are essential for growth and development. Furthermore, dietary deficiencies in zinc and iron were sure to have an effect on their population structure, especially through impairing successful reproduction (White, 1999). Santley et al. (1985) believe that the Maya had trouble replacing themselves, as their fertility rates declined and mortality rates increased, further aggravated by a lack of protein in their diet. Part of this is thought to be due to the nutritional stress placed on the people, and also because of the disease burden that they were faced with.
Even before the arrival of the Europeans and their accompanying illnesses, the pre-Columbian societies were constantly subject to infections and pathologies related to disease and parasites- this has been confirmed by evidence from human coprolites, mummified soft tissue and the remains of skeletons (Sharer, 1994). Complex ecosystems like tropical rainforests are often much greater hosts of infectious and parasitic organisms than simpler temperate ecosystems, and this has always been the situation.
Wilkinson (1995) proposed that a yellow fever epidemic migrating north from Brazil (where evidence of endemic varieties have been found) could have caused the Maya collapse. His speculations are based on similar patterns of the Maya decline to the declines of other populations who were exposed to yellow fever for the first time. Despite this, there is no direct archaeological evidence for this.
As with the crops like maize (discussed in my previous post), it is thought that the human population also became more prone to diseases due to agricultural intensification and settlement expansion. Such environmental changes would have led to an increase in insects (vectors) transmitting human pathogens and subsequently made infections more common. Additionally, through the reduction of other potential hosts, in particular the deer and other game hunted by the Maya, contact between vector organisms and the people was probably maximised. This would have further increased the likelihood of infections by vector-borne diseases, especially as the population grew throughout the Classic period (Folan et al., 2000).
And it doesn’t end there. The vicious cycle between nutrition and infection would have further amplified effects of disease through positive feedbacks. For example, malnutrition would increase the severity of infections, which would then further exacerbate nutrition deficiencies and reduce immunity to future infections. The reconstruction of the Late Classic Maya food production carried out by Santley et al. (1985) supports these theories. They suspected that the low fertility rates and high mortality rates, especially among the very young and very old, led to an inevitable decline in population, as each age cohort decreased in size through time.
One piece of evidence that I found particularly interesting was that they found a marked reduction in the mean stature of non-elites and elites (who were generally taller due to better diets and health) alike from looking at skeletal data. This coincides with the theory that together with agricultural failure and increased diseases, diets became poorer.
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