Turnover-pulse hypothesis

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The Turnover-pulse hypothesis was constructed by paleoanthropologist Elisabeth Vrba used to gauge the rate of survival and adaptations within species. The theory's key factors are based on the sequence of species in the palaeontology of related genera, and environmental aspects in adaptation, survival and extinction.

Theory[edit]

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 experience more extinctions, and a "pulse" of positive and random speciation within their groups.

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

This hypothesis was developed to explain the different patterns of evolution seen in African antelopes. Later, it was used in an attempt to explain the speciation and distribution that lead to early hominins and subsequently Homo sapiens.

The 2.5 Million Year Event[edit]

A well-known example is 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, so the hypothesis states, that many species attempted to move from their now uninhabitable habitats and later developed different adaptations in their new environments, evolving into different species.

Application in paleoanthropology[edit]

Support for the hypothesis comes from the concurrent split in Australopithecus afarensis and Paranthropus robustus, which each 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.