Life 2016, 6(3), 25; doi:10.3390/life6030025
The Cosmic Zoo: The (Near) Inevitability of the Evolution of Complex, Macroscopic Life
William Bains 1,2,* and Dirk Schulze-Makuch 3,4
1 Department of Earth, Atmospheric and Planetary Science, MIT, 77 Mass. Ave., Cambridge, MA 02139, USA
2 Rufus Scientific Ltd., 37 The Moor, Melbourn, Royston, Herts SG8 6ED, UK
3 School of the Environment, Washington State University, Pullman, WA 99164, USA
4 Center for Astronomy and Astrophysics, Technical University Berlin, Berlin 10623, Germany
* Author to whom correspondence should be addressed.
Academic Editor: David Deamer
Received: 26 March 2016 / Revised: 17 June 2016 / Accepted: 22 June 2016 / Published: 30 June 2016
Life on Earth provides a unique biological record from single-cell microbes to technologically intelligent life forms. Our evolution is marked by several major steps or innovations along a path of increasing complexity from microbes to space-faring humans. Here we identify various major key innovations, and use an analytical toolset consisting of a set of models to analyse how likely each key innovation is to occur. Our conclusion is that once the origin of life is accomplished, most of the key innovations can occur rather readily. The conclusion for other worlds is that if the origin of life can occur rather easily, we should live in a cosmic zoo, as the innovations necessary to lead to complex life will occur with high probability given sufficient time and habitat. On the other hand, if the origin of life is rare, then we might live in a rather empty universe.
Keywords: transition; key innovation; complexity; evolution; multicellularity; origin of life; great filter
This is an open access article distributed under the Creative Commons Attribution License (CC BY) which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
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