Turnover-pulse hypothesis

"The Turnover-pulse hypothesis" was constructed by paleoanthropologist Elizabeth Vrba used to gauge the rate of survival and adaptations within species. The theories key factors are entirely based on environmental aspects in adaptation, survival and extinction.

Theory

Ecosystems periodically experience significant disruptions, these in turn result in mass extinctions. Extinctions in turn hurt specialists more than generalists, where the generalists will in turn thrive within the environment by utilizing new environmental opportunities, or by moving elsewhere in diaspora to take advantage of other environments. The specialists will however experience a "pulse" of positive and random speciation within themselves.

These two events lead to more specialists in isolated areas whereas the generalists will become more spread out.

This hypothesis is used in an attempt to explain the speciation and distrubution that inevitably lead to early hominins and subsequently "Homo sapiens".

The 2.5 Million Year Event

A well known example that applies to the theory revolves around an episode known as the 2.5 million year event, in which a mass fluctuation of temperature occurred 2.5 million years BP, causing a rapid burst of speciation. It was during this event that the hypothesis states many organisms attempted to move from there now uninhabitable environments and later respectively developed different adaptations to their new environments, evolving into different organisms.

Application in Paleoanthropology

Evidence of the hypothesis points to the concurrent split in "Australopithecus afarensis", and "Paranthropus robustus" which were of the same species however they had developed separate traits in separate regions around the same time.

Counter-evidence points to the presence of "Homo habilis" and the lack of evidence that would support significant mutations occurring within that species in that same time frame.