Editing Fermi paradox (section)

==== Extraterrestrial life is rare or non-existent ====
{{main|Rare Earth hypothesis|Firstborn hypothesis}}
Those who think that intelligent [[extraterrestrial life]] is (nearly) impossible argue that the conditions needed for the evolution of life—or at least the [[evolution of biological complexity]]—are rare or even unique to Earth. Under this assumption, called the [[rare Earth hypothesis]], a rejection of the [[mediocrity principle]], complex multicellular life is regarded as exceedingly unusual.<ref name="rare-earth">{{cite book |title=Rare Earth: Why Complex Life is Uncommon in the Universe |first1=Peter D. |last1=Ward |author-link1=Peter Ward (paleontologist) |first2=Donald |last2=Brownlee |author-link2=Donald Brownlee |year= 2000 |page=368 |publisher=Springer |edition=1st |isbn=978-0-387-98701-9}}</ref>

The rare Earth hypothesis argues that the evolution of biological complexity requires a host of fortuitous circumstances, such as a [[galactic habitable zone]], a star and planet(s) having the requisite conditions, such as enough of a [[Circumstellar habitable zone|continuous habitable zone]], the advantage of a giant guardian like Jupiter and a large [[natural satellite|moon]], conditions needed to ensure the planet has a [[magnetosphere]] and [[plate tectonics]],<ref>{{cite journal |last1=Stern |first1=Robert J. |last2=Gerya |first2=Taras V. |title=The importance of continents, oceans and plate tectonics for the evolution of complex life: implications for finding extraterrestrial civilizations |journal=Scientific Reports |date=12 April 2024 |volume=14 |issue=1 |page=8552 |doi=10.1038/s41598-024-54700-x |pmid=38609425 |pmc=11015018 |bibcode=2024NatSR..14.8552S |language=en |issn=2045-2322}}</ref> the chemistry of the [[lithosphere]], [[atmosphere]], and oceans, the role of "evolutionary pumps" such as massive [[glaciation]] and rare [[Meteoroid#Bolide|bolide]] impacts. Perhaps most importantly, advanced life needs whatever it was that led to the transition of (some) [[prokaryote|prokaryotic cells]] to [[eukaryote|eukaryotic cells]], [[sexual reproduction]] and the [[Cambrian explosion]].

In his book ''[[Wonderful Life (book)|Wonderful Life]]'' (1989), Stephen Jay Gould suggested that if the "tape of life" were rewound to the time of the Cambrian explosion, and one or two tweaks made, human beings probably never would have evolved. Other thinkers such as Fontana, Buss, and Kauffman have written about the self-organizing properties of life.<ref>''The Nature of Nature: Examining the Role of Naturalism in Science'', editors Bruce Gordon and William Dembski,
[https://books.google.com/books?id=pe5nAwAAQBAJ&pg=PT491 Ch. 20 "The Chain of Accidents and the Rule of Law: The Role of Contingency and Necessity in Evolution"] by Michael Shemer, published by Intercollegiate Studies Institute, 2010.</ref>