Format

Send to

Choose Destination
Proc Biol Sci. 2017 Jun 28;284(1857). pii: 20171039. doi: 10.1098/rspb.2017.1039.

Hierarchical complexity and the size limits of life.

Author information

1
Department of Geological Sciences, Stanford University, Stanford, CA 94305, USA naheim@stanford.edu.
2
Department of Geological Sciences, Stanford University, Stanford, CA 94305, USA.
3
Department of Integrative Biology, University of California, Berkeley, CA 94720, USA.
4
Department of Biology, University of Hawaii, Hilo, HI 96720, USA.
5
Florida Museum of Natural History, University of Florida, Gainesville, FL 32611, USA.
6
School of Biological Sciences, University of Nebraska-Lincoln, Lincoln, NE 68588, USA.
7
Department of Biology, Duke University, Durham, NC 27708, USA.
8
Department of Biological Sciences, Benedictine University, Lisle, IL 60532, USA.
9
Department of Biology, University of New Mexico, Albuquerque, NM 87131, USA.
10
Department of Mathematics and Statistics, Swarthmore College, Swarthmore, PA 19081, USA.

Abstract

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.

KEYWORDS:

body size; complexity; evolution; hierarchy; macroecology; macroevolution

PMID:
28637850
PMCID:
PMC5489738
DOI:
10.1098/rspb.2017.1039
[Indexed for MEDLINE]
Free PMC Article

Supplemental Content

Full text links

Icon for Atypon Icon for PubMed Central
Loading ...
Support Center