InterJournal Complex Systems, 551
Status: Accepted
Manuscript Number: [551]
Submission Date: 20515
The Evolution of an Ecosystem: Pleistocene Extinctions
Author(s): Anonymous

Subject(s): CX.35, CX.34, CX.46

Category: Brief Article

Abstract:

It is generally assumed that evolution is an issue of looking at how the species fits into its environment. This paper suggests that we over-constrain our thinking on evolution we should be thinking of how the species and the ecosystem evolve together. The current theories of the Pleistocene extinction (Climate change and Overhunting by H. sapiens) are inadequate. Neither explains why: (1) browsers, mixed feeders and non-ruminant grazer species suffered most, while ruminant grazers like bison generally survived, (2) surviving mammal species including both subspecies of bison were sharply diminished in size; and (3) vegetative environments shifted from plaid to striped (Guthrie, 1980.) Climate change theories do not explain why mammoths and other megaherbivores survived changes of similar magnitude. Although flawed, the simple overkill hypothesis does link the extinctions and the arrival of H. sapiens. However, they omit the reciprocal impact of prey decline on H. Sapiens; standard predator-prey models, which include this effect, demonstrate that predators cannot hunt their prey to extinction without themselves succumbing to starvation. An alternate scenario and computer simulation (available on the internet from http://quaternary.net/extinct2000/) characterized by a boom/bust population pattern is presented. It suggests that H. sapiens reduced predator populations, causing a herbivore population boom, leading to overgrazing of trees and grass, resulting in environmental exhaustion and extinction of herbivores. If true, bison survival through the Pleistocene may be accounted for thus: herbivore population explosion created a condition of scarcity in which there was selective pressure favoring animals that could extract maximum energy from low quality forage to survive and reproduce. As a new Holocene stability emerged Holocene bison split into two sub-species (B. bison bison [plains bison] and B. bison athabascae [woodland bison]) that fit and maintained the emerging "striped" environments

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