Abstract
A recently improved understanding of gut immunity has merged with current thinking in biological and medical science, pointing to an apparent function of the mammalian cecal appendix as a safe-house for symbiotic gut microbes, preserving the flora during times of gastrointestinal infection in societies without modern medicine. This function is potentially a selective force for the evolution and maintenance of the appendix, and provides an impetus for reassessment of the evolution of the appendix. A comparative anatomical approach reveals three apparent morphotypes of the cecal appendix, as well as appendix-like structures in some species that lack a true cecal appendix. Cladistic analyses indicate that the appendix has evolved independently at least twice (at least once in diprotodont marsupials and at least once in Euarchontoglires), shows a highly significant (P < 0.0001) phylogenetic signal in its distribution, and has been maintained in mammalian evolution for 80 million years or longer.
Original language | English (US) |
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Pages (from-to) | 1984-1999 |
Number of pages | 16 |
Journal | Journal of Evolutionary Biology |
Volume | 22 |
Issue number | 10 |
DOIs | |
State | Published - Oct 2009 |
Keywords
- Appendix
- Cecum
- Cladistic
- Lagomorphs
- Marsupials
- Morphology
- Parsimony
- Primates
- Rodents
- Vermiform
ASJC Scopus subject areas
- Ecology, Evolution, Behavior and Systematics