Turnover-pulse hypothesis
Encyclopedia
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.
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
.
. It was during this event, so the hypothesis
states, that many species attempted to move from their now uninhabitable habitat
s and later developed different adaptation
s in their new environments, evolving into different species.
, and Paranthropus robustus
which 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.
Genera
Genera is a commercial operating system and development environment for Lisp machines developed by Symbolics. It is essentially a fork of an earlier operating system originating on the MIT AI Lab's Lisp machines which Symbolics had used in common with LMI and Texas Instruments...
, and environmental aspects in adaptation, survival and extinction.
Theory
Ecosystems periodically experience significant disruptions, these in turn result in mass extinctions. Extinctions in turn hurt specialistsGeneralist and specialist species
A generalist species is able to thrive in a wide variety of environmental conditions and can make use of a variety of different resources . A specialist species can only thrive in a narrow range of environmental conditions or has a limited diet. Most organisms do not all fit neatly into either...
more than generalists
Generalist and specialist species
A generalist species is able to thrive in a wide variety of environmental conditions and can make use of a variety of different resources . A specialist species can only thrive in a narrow range of environmental conditions or has a limited diet. Most organisms do not all fit neatly into either...
, 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
Speciation
Speciation is the evolutionary process by which new biological species arise. The biologist Orator F. Cook seems to have been the first to coin the term 'speciation' for the splitting of lineages or 'cladogenesis,' as opposed to 'anagenesis' or 'phyletic evolution' occurring within lineages...
and distribution
Cline (population genetics)
In biology, an ecocline or simply cline describes an ecotone in which a series of biocommunities display continuous gradient...
that lead to early hominins and subsequently Homo sapiens
Human
Humans are the only living species in the Homo genus...
.
The 2.5 Million Year Event
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 speciationSpeciation
Speciation is the evolutionary process by which new biological species arise. The biologist Orator F. Cook seems to have been the first to coin the term 'speciation' for the splitting of lineages or 'cladogenesis,' as opposed to 'anagenesis' or 'phyletic evolution' occurring within lineages...
. It was during this event, so the hypothesis
Hypothesis
A hypothesis is a proposed explanation for a phenomenon. The term derives from the Greek, ὑποτιθέναι – hypotithenai meaning "to put under" or "to suppose". For a hypothesis to be put forward as a scientific hypothesis, the scientific method requires that one can test it...
states, that many species attempted to move from their now uninhabitable habitat
Habitat
* Habitat , a place where a species lives and grows*Human habitat, a place where humans live, work or play** Space habitat, a space station intended as a permanent settlement...
s and later developed different adaptation
Adaptation
An adaptation in biology is a trait with a current functional role in the life history of an organism that is maintained and evolved by means of natural selection. An adaptation refers to both the current state of being adapted and to the dynamic evolutionary process that leads to the adaptation....
s in their new environments, evolving into different species.
Application in Paleoanthropology
Evidence of the hypothesis points to the concurrent split in Australopithecus afarensisAustralopithecus afarensis
Australopithecus afarensis is an extinct hominid that lived between 3.9 and 2.9 million years ago. A. afarensis was slenderly built, like the younger Australopithecus africanus. It is thought that A...
, and Paranthropus robustus
Paranthropus robustus
Paranthropus robustus was originally discovered in Southern Africa in 1938. The development of P. robustus, namely in cranial features, seemed to be aimed in the direction of a "heavy-chewing complex"...
which developed separate traits in separate regions around the same time.
Counter-evidence points to the presence of Homo habilis
Homo habilis
Homo habilis is a species of the genus Homo, which lived from approximately at the beginning of the Pleistocene period. The discovery and description of this species is credited to both Mary and Louis Leakey, who found fossils in Tanzania, East Africa, between 1962 and 1964. Homo habilis Homo...
and the lack of evidence that would support significant mutations occurring within that species in that same time frame.