What Caused the Collapse of Ancient Civilizations?

Introduction

I will investigate these questions in this lab report:

• What is the role of climate change in the Mayan collapse?

• What is the role of elite behaviours in the Mayan collapse?

• What do the possible causes of the Mayan collapse imply for our society?

Data

library(tidyverse)
library(here)
library(tidyr)

mayan_hiero <-
  readxl::read_excel(here("data/mayan_hiero_inscription_dates.xlsx"))

Tikal_Hg <-
  readxl::read_excel(here("data/mayan_tikal_Hg_in_sediment.xlsx"))

oxygen_isotope <-
  read_csv(here("data/oxygen_isotope_data_yok_i_ stalagmite.csv"))

mayan_dates_and_periods <- 
  read_csv(here("data/mayan_dates_and_periods_summary.csv")) %>%
  mutate(start_date = parse_number(start_date))

# things for inline R code
how_many_inscriptions <- nrow(mayan_hiero)
how_many_sediment_samples <- nrow(Tikal_Hg)

The data included from Hoggarth et al. (2016) included 128 inscriptions. The data included from Lentz et al. (2020) explored 35 sediment samples to explore mercury (Hg) levels. The data from Kennett et al. (2012) examines detailed climate record derived from a stalagmite collection cave in Belize centered in Classic Maya settlement.

Visualization

Mayan civilization during up to the early classic period was characterized by growth and flourishment, peaking and seeing decline during the late classic until irreversible collapse during the terminal classic time period. The data below visualizes the development of hieroglyphs in Chichén Itzá and concentration of mercury levels found in the Tikal water reservoirs.

# prepare the Hg data
Tikal_Hg_clean <-
Tikal_Hg %>%
  separate(`Depth and context`,
           into = c("Depth", "Context"),
           sep = ":") %>%
  rowwise() %>%
  mutate(mean_hg = mean(c(`Rep. 1`, `Rep. 2`, `Rep. 3`))) %>%
  mutate(period = factor(Context,
                          mayan_dates_and_periods$period))

# prepare the inscription data
mayan_hiero_clean <-
mayan_hiero %>%
  inner_join(mayan_dates_and_periods,
             join_by(between(`Gregorian Date AD`,
                             start_date,
                             end_date))) %>% 
  mutate(period = factor(period,
                         mayan_dates_and_periods$period))

library(ggbeeswarm)
library(cowplot)

p_hi <- 
  ggplot(mayan_hiero_clean) + 
  aes(period) + 
  geom_bar() + 
  scale_x_discrete(drop = FALSE, 
                   guide = guide_axis(n.dodge = 2)) + 
  ylab("Hieroglyphic inscriptions") + 
  theme_minimal()
  
p_hg <- 
ggplot(Tikal_Hg_clean) + 
  aes(period,
      mean_hg) +
  geom_boxplot() + 
  geom_quasirandom() + 
  scale_x_discrete(drop = FALSE,
                   guide = guide_axis(n.dodge = 2),
                   name = "") + 
  ylab("Hg concentration (ug/g)") +
  geom_hline(yintercept =  1,
             colour = "red") +
  theme_minimal()

# create a panel of plots
plot_grid(p_hi,
          p_hg,
          ncol = 1)

In Figure 1, we can see that during the early classic period, less than 15 hieroglyphs, with a median Hg mercury of lower than 2 ug/g

We can see that during the LCP/TCP period there were over 60 hieroglyphs with a median Hg mercury of 17 ug/g. This period has been linked to a drastic decline in Mayan civilization.

library(ggtext)

ggplot(oxygen_isotope) + 
  aes(`yr AD`, 
      `δ18O\r\n(VPDB)`,
      colour = `δ18O\r\n(VPDB)`) +
  geom_line() +
  scale_y_reverse(name = "&delta;*<sup>18</sup>0 (&permil;VPDB)") +
  scale_color_viridis_c() +
  theme(axis.title.y = element_markdown() ) + 
  annotate("text",
           label = mayan_dates_and_periods$period,
           x =     mayan_dates_and_periods$midpoint,
           y = -5.0,
           angle = 90,
           size = 3) +
  geom_vline(data = mayan_dates_and_periods,
             aes(xintercept = start_date),
             colour = "grey70") + 
  scale_x_continuous(limits = c(0, 2000)) +
  scale_color_viridis_c()

In Figure 2 we can see the climate record derived from a collection of stalagmites. It shows an increase in precipitation from the early classic period (3.25 δ18O), to the late classic period (> 4.5 δ18O), then end of the post classic period down to 3 δ180.

Conclusion

The Mesoamerican Terminal Classic time period that proceed the late classic saw drastic civilization collapse during 800-925 A.D. Within a hundred years, the Mayan cities went from flourishing to a permanent decline and city abandonment. Tikal was already established during the Middle and Late Classic period which was positioned near seasonal wetlands. The best recorded time for many Maya lineages like Tikal were around Early Classic Period around 450-500 C.E. which were linked to high rainfall, and growing political influence of Mayan lineages.

In Figure 1 the increase in hieroglyphs during the Terminal Classic may point to an increase in interpolity warefare. In addition, Figure 1 shows the higher levels of toxic mercury in water sources, and Figure 2 shows the drying period, a reduction in precipitation. All occurred jointly after the early/middle classic period showing the linkage of multiple sources to abandonment of cities.

Elite behaviors that have favored and made more hieroglyphs, which were made using toxic mercury because of it’s naturally red pigment, could have led to the demise of some Mayan societies because it’s widespread use.

This behavior leading to the increased use of mercury in hieroglyphics could be another explanation for the collapse. Mercury contaminated water sources would have made caused widespread illness.

People often push western ideology and fears of war, which western cultures were engulfed in. Although war has been linked to their collapse, there are many other potential reasons why the people left these ancient cities such as political divide, and climate change such as dwindling resources, toxic mercury contamination, drought, and famine. And they did not just die off in war like commonly thought. Many of the people moved out of those cities and continued to live on. Other cultures were not so engulfed in war, other fears and views shouldn’t be pushed on to other societies as to ensure respect for the people from those societies that still live on today.

References

Douglas J. Kennett et al. ,Development and Disintegration of Maya Political Systems in Response to Climate Change.Science338,788-791(2012).DOI:10.1126/science.1226299

Hoggarth, J. A., Breitenbach, S. F. M., Culleton, B. J., Ebert, C. E., Masson, M. A., & Kennett, D. J. (2016). The political collapse of Chichén Itzá in climatic and cultural context. Global and Planetary Change, 138, 25-42. ISSN 0921-8181. https://doi.org/10.1016/j.gloplacha.2015.12.007

Lentz, D.L., Hamilton, T.L., Dunning, N.P. et al. Molecular genetic and geochemical assays reveal severe contamination of drinking water reservoirs at the ancient Maya city of Tikal. Sci Rep 10, 10316 (2020). https://doi-org.offcampus.lib.washington.edu/10.1038/s41598-020-67044-z