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Coevolution of the mammalian middle ear and neocortex
1Department of Geological Sciences and Vertebrate Paleontology Laboratory, University of Texas, Austin, TX 78712, USA.
Science (New York, N.Y.)
|August 2, 1996
Summary
The mammalian middle ear evolved with neocortex growth, detaching from the jaw. This developmental process in mammals mirrors evolutionary changes, linking brain and ear development.
Area of Science:
- Evolutionary biology
- Paleontology
- Developmental biology
Background:
- The mammalian middle ear evolved from a jaw-attached structure in tetrapods to a detached chain in mammals.
- Neocortex evolution in mammals coincided with the detachment of the middle ear bones.
Purpose of the Study:
- To investigate the evolutionary and developmental link between neocortex growth and mammalian middle ear formation.
Main Methods:
- Phylogenetic analysis using x-ray computed tomography (CT) on fossilized and recent crania.
- Comparative developmental studies of mammalian (didelphid) auditory chain formation.
Main Results:
- Phylogenetic analysis suggests differential neocortex growth influenced mammalian middle ear evolution.
- Mammalian development shows the auditory chain initially attached to the mandible, detaching later.
- In didelphids, auditory chain separation occurs as the neocortex undergoes significant growth post-birth.
Conclusions:
- Neocortex expansion played a crucial role in the evolutionary transformation of the mammalian middle ear.
- The developmental pathway of the middle ear in mammals recapitulates its phylogenetic history.
- Differential brain growth is implicated in the unique mammalian middle ear structure.