Fig 1.
A-Population density on the x-axis and per capita fitness on the y-axis.
The four black curves illustrate the relationship between population density and per capita fitness at four different levels of climate driven resource productivity, C. The arrows indicate how a population may change over time, with demographic transitions occurring only if climate change increases the productivity of resources (r = 0.25, S = 0, A1 − A2 = 0, Bi = 0, d = 0) B-Population density on the x-axis and per capita fitness on the y-axis. The four black curves illustrate the relationship between population density and per capita fitness for successively more productive infrastructure systems (r = 0.25, S = 0, Bi = 0, d = 0, C = 1).
Fig 2.
A-Demographic transitions in a population system beginning at A = 0. All other parameters held constant: S = 0.5, d = 25, C = 1, B2 = −0.3, and r = 0.25.
The delayed impact of human populations on the resource results in an overshoot and recession. B-Population dynamics over time with a delay. As A = A2 − A1 increases, the overshoot and recession increases in length and intensity. C-Demographic transitions in a population system beginning at A = 0, C = 1. In each successive curve, we hold A = 0.5, S = 0.5, d = 25, B2 = −0.3, and r = 0.25. As C increases, equilibrium population size also increases, the size of the demographic transition decreases, and the overshoot and recession intensifies. D-Population dynamics over time. As C increases, the size of the overshoot and recession increases.
Fig 3.
A–Population density the x-axis and per capita fitness on the y-axis.
The black curves illustrate the relationship between population density and per capita fitness when C = 1 and C = 3. All other parameters are held equal at A = 0.5, S = 0.5, d = 25, B2 = −0.3, r = 0.25, and Delta = 0.01. The green dashed curve illustrates what would occur in an environment with a constant mean climate. The red dashed curve illustrates the trend of the stochastic black curve when a demographic transition occurs. B–Change in population over time in stationary and stochastic climates of C = 1 and C = 3. The red curves illustrate the demographic transitions induced by climate variability highlighted in Fig 3A.
Fig 4.
Map of the archaeological regions discussed in the text.
Vector base map data available via CC BY license from Natural Earth (public domain at http://www.naturalearthdata.com) and The Humanitarian Data Exchange (public domain at https://data.humdata.org/dataset/cod-ab-arg). Figure produced using ArcGIS Pro 3.2 software.
Table 1.
Summary of changes in subsistence and technology by four phases of time in the Northern, Central, and Southern areas of CWA.
Fig 5.
A-Plot of mean KDE (x-axis) against the per capita growth rate of the mean KDE (y-axis) in the Northern area.
Data points connect in order from oldest to youngest. The arrows indicate the direction of change over time. Red dots estimate the central KDE value when one or more cycle is detected. B-Plot of mean KDE (x-axis) against the per capita growth rate of the mean KDE (y-axis) in the Central area. C-Plot of mean KDE (x-axis) against the per capita growth rate of the mean KDE (y-axis) in the Southern area.
Fig 6.
A-Mean KDE (black curve) and 95% confidence envelope of simulated KDEs (grey shading) in the Northern area.
B-The per capita growth rate of the mean KDE over time. The blue dashed boxes indicate periods of repeated demographic transitions. C-Violin plots of δ13C carbonate by phases. Black dots indicate the medians of the distributions and lines illustrate the change in median between phases. Numbers indicate the value of a pairwise Conover test. ** indicates p<0.05.
Fig 7.
A-Mean KDE (black curve) and 95% confidence envelope of simulated KDEs (grey shading) in the Central area.
B-The per capita growth rate of the mean KDE over time in the Central area. The blue dashed boxes indicate periods of potential demographic transitions. C-Violin plots of δ13C carbonate by phases. Black dots indicate the medians of the distributions and lines illustrate the change in median between phases. Numbers indicate the value of a pairwise Conover test. ** indicates p<0.05.
Fig 8.
A-Mean KDE (black curve) and 95% confidence envelope of simulated KDEs (grey shading) in the Southern area.
B-The per capita growth rate of the mean KDE over time in the South. The blue dashed boxes indicate periods of potential demographic transitions. C-Violin plots of δ13C carbonate by phases. Black dots indicate the medians of the distributions and lines illustrate the change in median between phases. Numbers indicate the value of a pairwise Conover test. ** indicates p<0.05.
Fig 9.
A-Modeled (green curve) and actual mean KDE values over time in the Northern area.
Grey shaded area is the confidence envelope of predicted mean KDE values based on modeled rainfall. B-Pointwise causal effect of suspected subsistence/social innovation on the mean KDE in the Northern area. C-Modeled (green curve) and actual mean KDE values over time in the Central area. Grey shaded area is the confidence envelope of predicted mean KDE values based on modeled rainfall. D- Pointwise causal effect of suspected subsistence innovation on the mean KDE in the Central area. E-Modeled (green curve) and actual mean KDE values over time in the Southern area. Grey shaded area is the confidence envelope of predicted mean KDE values based on modeled rainfall. F-Pointwise causal effect of suspected subsistence innovation on the mean KDE in the Southern area.
Fig 10.
A-Modeled (green curve) and actual mean KDE values over time in the Northern area.
Grey shaded area is the confidence envelope of predicted mean KDE values based on modeled rainfall. B- Pointwise causal effect of suspected subsistence innovation on the mean KDE in the Northern area. C-Modeled (green curve) and actual mean KDE values over time in the Central area. Grey shaded area is the confidence envelope of predicted mean KDE values based on modeled rainfall. D- Pointwise causal effect of suspected subsistence innovation on the mean KDE in the Central area. E-Modeled (green curve) and actual mean KDE values over time in the Southern area. Grey shaded area is the confidence envelope of predicted mean KDE values based on modeled rainfall. F-Pointwise causal effect of suspected subsistence innovation on the mean KDE in the Southern area.