Directionality in the History of Life: Diffusion from the Left Wall or Repeated Scaling of the Right?
Access StatusFull text of the requested work is not available in DASH at this time ("restricted access"). For more information on restricted deposits, see our FAQ.
MetadataShow full item record
CitationKnoll, Andrew H., and Richard K. Bambach. 2000. Directionality in the history of life: Diffusion from the left wall or repeated scaling of the right? Paleobiology 26(4): 1-14.
AbstractIssues of directionality in the history of life can be framed in terms of six major evolutionary steps, or megatrajectories (cf. Maynard Smith and Szathmary 1995): (1) evolution from the origin of life to the last common ancestor of extant organisms, (2) the metabolic diversification of bacteria and archaea, (3) evolution of eukaryotic cells, (4) multicellularity, (5) the invasion of the land and (6) technological intelligence. Within each megatrajectory, overall diversification conforms to a pattern of increasing variance bounded by a right wall as well as one on the left. However, the expanding envelope of forms and physiologies also reflects-at least in part-directional evolution within clades. Each megatrajectory has introduced fundamentally new evolutionary entities that garner resources in new ways, resulting in an unambiguously directional pattern of increasing ecological complexity marked by expanding ecospace utilization. The sequential addition of megatrajectories adheres to logical rules of ecosystem function, providing a blueprint for evolution that may have been followed to varying degrees wherever life has arisen.
Citable link to this pagehttp://nrs.harvard.edu/urn-3:HUL.InstRepos:3190374
- FAS Scholarly Articles