Note to users. If you're seeing this message, it means that your browser cannot find this page's style/presentation instructions -- or possibly that you are using a browser that does not support current Web standards. Find out more about why this message is appearing, and what you can do to make your experience of our site the best it can be.

Science 12 June 1987:
Vol. 236. no. 4807, pp. 1437 - 1441
DOI: 10.1126/science.236.4807.1437
Prev | Table of Contents | Next

Articles

Asymmetry of Lineages and the Direction of Evolutionary Time

STEPHEN JAY GOULD 1, NORMAN L. GILINSKY 2, and REBECCA Z. GERMAN 3

1 Museum of Comparative Zoology, Harvard University, Cambridge, MA 02138.
2 Department of Geological Sciences, Virginia Polytechnic Institute, Blacksburg, VA 24061.
3 School of Dental Medicine, Washington University, St. Louis, MO 63130.

Evolutionary time has a characteristic direction as demonstrated by the asymmetry of clade diversity diagrams in large statistical samples. Evolutionary groups generally concentrate diversity during their early histories, producing a preponderance of bottom-heavy clades among those that arise early in the history of a larger group. This pattern holds across taxonomic levels and across differences in anatomy and ecology (marine invertebrates, terrestrial mammals). The quantitative study of directionality in life's history (replacing vague, untestable, and culturally laden notions of "progress") should receive more attention from paleobiologists.


THIS ARTICLE HAS BEEN CITED BY OTHER ARTICLES:
Symmetric waxing and waning of marine invertebrate genera.
M. Foote (2007)
Paleobiology 33, 517-529
   Abstract »    Full Text »    PDF »
A Cambrian Peak in Morphological Variation Within Trilobite Species.
M. Webster (2007)
Science 317, 499-502
   Abstract »    Full Text »    PDF »
History and Explanation in Archaeology.
M. J. O'Brien and R. L. Lyman (2004)
Anthropological Theory 4, 173-197
   Abstract »    PDF »
Evolutionary trends in coiling of tropical Paleogene planktic foraminifera.
(2001)
Paleobiology 27, 327-347
Contrasting evolutionary flexibility in sister groups: disparity and diversity in Mesozoic atelostomate echinoids.
(2000)
Paleobiology 26, 56-79
Colonial Systems.
J. Porra (1999)
Information Systems Research 10, 38-69
   Abstract »    PDF »
Asymmetries of Clade Shape and the Direction of Evolutionary Time.
N. L. GILINSKY, S. J. GOULD, and R. Z. GERMAN (1989)
Science 243, 1613-1614
   PDF »
Response: Asymmetries of Clade Shape and the Direction of Evolutionary Time.
J. A. KITCHELL and N. MACLEOD (1989)
Science 243, 1614-1615
   PDF »
Time in the geomorphology of Western Australia.
K.-H. Wyrwoll and K.-H. Wyrwoll (1988)
Progress in Physical Geography 12, 237-263
   PDF »
Macroevolutionary Interpretations of Symmetry and Synchroneity in the Fossil Record.
J. A. KITCHELL and N. MACLEOD (1988)
Science 240, 1190-1193
   Abstract »    PDF »


To Advertise     Find Products

Science. ISSN 0036-8075 (print), 1095-9203 (online)