Hierarchical complexity and the size limits of life.

Journal Article (Journal Article)

Over the past 3.8 billion years, the maximum size of life has increased by approximately 18 orders of magnitude. Much of this increase is associated with two major evolutionary innovations: the evolution of eukaryotes from prokaryotic cells approximately 1.9 billion years ago (Ga), and multicellular life diversifying from unicellular ancestors approximately 0.6 Ga. However, the quantitative relationship between organismal size and structural complexity remains poorly documented. We assessed this relationship using a comprehensive dataset that includes organismal size and level of biological complexity for 11 172 extant genera. We find that the distributions of sizes within complexity levels are unimodal, whereas the aggregate distribution is multimodal. Moreover, both the mean size and the range of size occupied increases with each additional level of complexity. Increases in size range are non-symmetric: the maximum organismal size increases more than the minimum. The majority of the observed increase in organismal size over the history of life on the Earth is accounted for by two discrete jumps in complexity rather than evolutionary trends within levels of complexity. Our results provide quantitative support for an evolutionary expansion away from a minimal size constraint and suggest a fundamental rescaling of the constraints on minimal and maximal size as biological complexity increases.

Full Text

Duke Authors

Cited Authors

  • Heim, NA; Payne, JL; Finnegan, S; Knope, ML; Kowalewski, M; Lyons, SK; McShea, DW; Novack-Gottshall, PM; Smith, FA; Wang, SC

Published Date

  • June 2017

Published In

Volume / Issue

  • 284 / 1857

Start / End Page

  • 20171039 -

PubMed ID

  • 28637850

Pubmed Central ID

  • PMC5489738

Electronic International Standard Serial Number (EISSN)

  • 1471-2954

International Standard Serial Number (ISSN)

  • 0962-8452

Digital Object Identifier (DOI)

  • 10.1098/rspb.2017.1039


  • eng