Chapter

A directional history of life (1825–31)

in Worlds Before Adam

Published by University of Chicago Press

Published in print July 2008 | ISBN: 9780226731285
Published online March 2013 | e-ISBN: 9780226731308 | DOI: http://dx.doi.org/10.7208/chicago/9780226731308.003.0013
A directional history of life (1825–31)

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This chapter traces how the history of life was coming to be seen ever more clearly as directional in character. Research on Tertiary faunas reinforced the increasing sense among geologists that the earth's faunas had indeed changed directionally throughout geohistory. Adolphe Brongniart's ambitious work on fossil plants had the same impact, on the larger scale of the whole fossil record, when he identified at least three major floras that had flourished successively in the course of geohistory, marked by the successive appearance of new major groups of plants and hence an increasing diversity and even, in some sense, progress. And Brongniart linked this with the intrinsic directionality inherent in the theory of a gradually cooling earth, as newly endorsed by the physicists: as the earth cooled, climates at its surface would have become progressively more temperate and more differentiated, while even the composition of the atmosphere might have changed in a similar way. This picture of the changing vegetation on a gradually cooling earth was already getting support from the discovery in the high Arctic of the characteristic large plants of the Coal formation, and even coal seams, together with equally tropical-looking corals and other marine fossils. This suggested strongly that the whole earth, even at this high latitude, had been tropical in climate at that extremely remote period of geohistory.

Keywords: Tertiaries; Tertiary faunas; geohistory; Adolphe Brongniart

Chapter.  7330 words.  Illustrated.

Subjects: History of Science and Technology

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