Asymmetry of lineages and the direction of evolutionary time.

@article{Gould1987AsymmetryOL,
  title={Asymmetry of lineages and the direction of evolutionary time.},
  author={Stephen J. Gould and N L Gilinsky and Rebecca Z German},
  journal={Science},
  year={1987},
  volume={236 4807},
  pages={1437-41}
}
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… CONTINUE READING