Hollings Cycle and the Evolution

New constraints are needed to give evolution a kick from time to time. By this view, response to catastrophes could even be seen as advantageous in the long run; for example, the Earth has been witness to several enormous catastrophes such as happened 65 Ma when an asteroid hit the planet and thereby created conditions and therefore new challenges. This is the 'creative destruction' of the Holling's cycle (see Figures 1-4). Other similar catastrophes that may have given the evolution a kick are summarized in Table 1.

Table 1 Significant mass extinctions

Million

Loss of

Geological

years

families

period

BP

(%)

Potential reason

Ordovician

440

25

Sudden global cooling

Devonian

370

19

Global climate change

Permian

245

54

Global climate change

induced by a bolide

Triassic

210

23

Most probably climatic

changes

Cretaceous

65

17

Asteroid strike

An additional example is the dramatic change of the climate in Africa c. 5 million years ago. Precipitation was significantly reduced and the rainforest was replaced by savanna. This presented a new challenge to the apes and made it more beneficial to walk on two legs. That started probably the evolution toward Homo sapiens. Development of a bigger brain volume probably also started by a somewhat random process: man became carnivorous, requiring a larger brain for hunting; coordinated teamwork during hunting, involving a communication network to facilitate information exchange, also led to bigger brains entailing a wider spectrum of amino acids.

See also: Adaptive Management and Integrative assessments; Biodiversity; Exergy; Succession; Panarchy.

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