The population ecology of hunter-gatherers and their prey

Abstract

In this paper we combine foraging theory and population biology models to simulate dynamic relationships between hunter-gatherers and their prey resources. Hunter-gatherer population growth responds to the net marginal rate of foraging; prey population growth responds logistically to exploitation. Thus conceived, the relationship between forager and prey biomass is time-dependent and nonlinear. It changes from stable equilibrium to damped and stable cycles with modest adjustments of input parameters. And, it produces the largest sustainable human population at intermediate levels of individual work effort. At equilibrium the forager takes all prey types with a pursuit and handling rate greater than or equal to its maintenance foraging rate. The structural properties of the model compel us to reject standard anthropological interpretations of the carrying capacity concept; they provide new insights on old issues such as original aflluence and intensification. Analysis of the interaction of human population, diet selection, and resource depletion requires microecological models in part because the relevant processes occur on time scales largely invisible to both ethnography and archaeology.

Periodic catastrophes over human evolutionary history are necessary to explain the forager population paradox

“…One limitation is that our demographic approach is not a bottoms-up population ecological model of density-dependent population growth and does not include environmental carrying capacity. Models invoking carrying capacity and density dependence with delayed feedbacks often show population crashes or oscillations (34,35,43), consistent with our findings. Our approach is silent about the mechanisms causing vital rate change but instead focuses on the demographic requirements for ZPG.…”

Periodic catastrophes over human evolutionary history are necessary to explain the forager population paradox

“…One limitation is that our demographic approach is not a bottoms-up population ecological model of density-dependent population growth and does not include environmental carrying capacity. Models invoking carrying capacity and density dependence with delayed feedbacks often show population crashes or oscillations (34,35,43), consistent with our findings. Our approach is silent about the mechanisms causing vital rate change but instead focuses on the demographic requirements for ZPG.…”

A Review and Synthesis of Late Pleistocene Extinction Modeling: Progress Delayed by Mismatches between Ecological Realism, Interpretation, and Methodological Transparency

“…Although extinction is possible, the model does not duplicate actual late Pleistocene survival-extinction patterns. These results are consistent with findings from another optimal foraging model (Winterhalder et al 1988), which demonstrates that communities with few prey species are not extinction-prone. A later multiprey simulation (Winterhalder and Lu 1997) suggests that long-term human residence in multiprey ecosystems with varied resources can lead both to single extinctions and the general loss of large species typical of late Pleistocene communities.…”

Prehistoric population history in eastern Fennoscandia

“…If both of these phenomena are real, we have here a case that also counters the more general idea of population growth induced broadening of diet (e.g. Winterhalder et al, 1988). However, it is likely that the lowering of the carrying capacity caused by productivity decline has an effect here, as carrying capacity going down and population going up can lead to the same result.…”

Periodic catastrophes over human evolutionary history are necessary to explain the forager population paradox

“…One limitation is that our demographic approach is not a bottoms-up population ecological model of density-dependent population growth and does not include environmental carrying capacity. Models invoking carrying capacity and density dependence with delayed feedbacks often show population crashes or oscillations (34,35,43), consistent with our findings. Our approach is silent about the mechanisms causing vital rate change but instead focuses on the demographic requirements for ZPG.…”

A Review and Synthesis of Late Pleistocene Extinction Modeling: Progress Delayed by Mismatches between Ecological Realism, Interpretation, and Methodological Transparency

“…Although extinction is possible, the model does not duplicate actual late Pleistocene survival-extinction patterns. These results are consistent with findings from another optimal foraging model (Winterhalder et al 1988), which demonstrates that communities with few prey species are not extinction-prone. A later multiprey simulation (Winterhalder and Lu 1997) suggests that long-term human residence in multiprey ecosystems with varied resources can lead both to single extinctions and the general loss of large species typical of late Pleistocene communities.…”

Prehistoric population history in eastern Fennoscandia

“…If both of these phenomena are real, we have here a case that also counters the more general idea of population growth induced broadening of diet (e.g. Winterhalder et al, 1988). However, it is likely that the lowering of the carrying capacity caused by productivity decline has an effect here, as carrying capacity going down and population going up can lead to the same result.…”

Periodic catastrophes over human evolutionary history are necessary to explain the forager population paradox

“…One limitation is that our demographic approach is not a bottoms-up population ecological model of density-dependent population growth and does not include environmental carrying capacity. Models invoking carrying capacity and density dependence with delayed feedbacks often show population crashes or oscillations (34,35,43), consistent with our findings. Our approach is silent about the mechanisms causing vital rate change but instead focuses on the demographic requirements for ZPG.…”

A Review and Synthesis of Late Pleistocene Extinction Modeling: Progress Delayed by Mismatches between Ecological Realism, Interpretation, and Methodological Transparency

“…Although extinction is possible, the model does not duplicate actual late Pleistocene survival-extinction patterns. These results are consistent with findings from another optimal foraging model (Winterhalder et al 1988), which demonstrates that communities with few prey species are not extinction-prone. A later multiprey simulation (Winterhalder and Lu 1997) suggests that long-term human residence in multiprey ecosystems with varied resources can lead both to single extinctions and the general loss of large species typical of late Pleistocene communities.…”

Prehistoric population history in eastern Fennoscandia

“…If both of these phenomena are real, we have here a case that also counters the more general idea of population growth induced broadening of diet (e.g. Winterhalder et al, 1988). However, it is likely that the lowering of the carrying capacity caused by productivity decline has an effect here, as carrying capacity going down and population going up can lead to the same result.…”