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Catastrophes and Lesser CalamitiesThe causes of mass extinctions$
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Tony Hallam

Print publication date: 2004

Print ISBN-13: 9780198524977

Published to Oxford Scholarship Online: November 2020

DOI: 10.1093/oso/9780198524977.001.0001

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The evolutionary significance of mass extinctions

The evolutionary significance of mass extinctions

10 The evolutionary significance of mass extinctions
Catastrophes and Lesser Calamities

Tony Hallam

Oxford University Press

Darwin was firmly of the opinion that biotic interactions, such as competition for food and space – the ‘struggle for existence’ – were of considerably greater importance in promoting evolution and extinction than changes in the physical environment. This is clearly brought out by this quotation from The Origin of Species: . . . Species are produced and exterminated by slowly acting causes . . . and the most important of all causes of organic change is one that is almost independent of altered . . . physical conditions, namely the mutual relation of organism to organism – the improvement of one organism entailing the improvement or extermination of others. . . . The driving force of competition in a crowded world is also stressed in another quotation presenting Darwin’s famous wedge metaphor: . . . In looking at Nature, it is most necessary . . . never to forget that every single organic being around us may be said to be striving to the utmost to increase in numbers; that each lives by a struggle at some period of its life; that heavy destruction inevitably falls either on the young or the old, during each generation . . . The face of Nature may be compared to a yielding surface, with ten thousand sharp wedges packed close together and driven inwards by incessant blows, sometimes one wedge being struck, and then another with greater force. . . . The implication of the Darwinian view concerning the dominance of biotic competition is that for each winner there is a loser – a kind of zero-sum game. It has been accepted more or less uncritically by generations of evolutionary biologists, but not until the 1970s did it become graced with a name – the Red Queen hypothesis. The story behind the emergence of this name is an interesting one. At the beginning of the 1970s the rather eccentric University of Chicago palaeobiologist Leigh Van Valen did some interesting research concerning the analysis of survivors of Phanerozoic taxa which suggested that the probability of a fossil group becoming extinct was more or less constant in time. To account for this, Van Valen put forward his Red Queen hypothesis.

Keywords:   Antarctica, Brazil, Chicxulub, Deccan Traps, Etendeta basalts, Gastropods, Jurassic, Madagascar, North Atlantic Igneous Province

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