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Asymmetric Broca's area in great apes
1Division of Psychobiology and Living Links Center, Yerkes Regional Primate Research Center, Emory University, Atlanta, Georgia 30322, USA. lrcbh@rmy.emory.edu
Nature
|December 6, 2001
Summary
Great apes share a brain asymmetry with humans in a key speech area. This suggests the neurological basis for language dominance predates human evolution and is not unique to our species.
Area of Science:
- Neuroscience
- Comparative Anatomy
- Evolutionary Biology
Background:
- Brodmann's area 44, part of Broca's area in the inferior frontal gyrus, is crucial for speech production.
- In humans, this area exhibits left-hemisphere dominance, which is linked to language lateralization.
- Understanding the evolutionary origins of this asymmetry is key to comprehending language evolution.
Purpose of the Study:
- To investigate whether the left-hemisphere asymmetry observed in human Brodmann's area 44 is present in other great ape species.
- To explore the evolutionary timeline of brain lateralization related to speech production.
Main Methods:
- Comparative analysis of Brodmann's area 44 in chimpanzees (Pan troglodytes), bonobos (Pan paniscus), and gorillas (Gorilla gorilla).
- Assessment of hemispheric size differences in this specific brain region across the studied species.
Main Results:
- A similar left-hemisphere dominance in Brodmann's area 44 was found in all three great ape species examined.
- This anatomical asymmetry mirrors the pattern observed in humans.
Conclusions:
- The neuroanatomical substrates for left-hemisphere dominance in speech production were present at least five million years ago.
- These findings indicate that such asymmetries are not exclusive to hominid evolution and likely have deeper evolutionary roots.
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