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Human paleontological evidence relevant to language behavior.
Human Neurobiology
|January 1, 1983
Summary
Paleoneurology reveals early hominid brain changes, including reduced visual cortex and expanded parietal areas. Later Homo fossils show enlarged frontal lobes and asymmetries, suggesting complex cognitive evolution and sexual dimorphism linked to social behaviors.
Area of Science:
- Paleoneurology
- Human Evolution
- Cognitive Neuroscience
Background:
- Cranial endocasts of early hominids offer insights into brain evolution, though fossil evidence is often fragmented.
- Early hominids like Australopithecus afarensis and africanus show some cerebral organization distinct from pongids.
Purpose of the Study:
- To analyze paleoneurological evidence for human cognitive evolution, including language origins.
- To investigate changes in cerebral organization and brain size in early hominid lineages.
- To explore the evolutionary basis of sexual dimorphism in the human brain and its relation to social behavior.
Main Methods:
- Analysis of endocranial portions from Australopithecus afarensis and africanus (Taung and A.L. 162-28).
- Examination of fossil evidence from the Homo lineage (1.8-2.0 million years old) for brain size, frontal lobe development, and asymmetries.
- Integration of modern human corpus callosum sexual dimorphism data with clinical and psychological evidence.
Main Results:
- Australopithecus specimens exhibit a reduction in primary visual striate cortex and a relative increase in parietal cortex.
- Homo lineage fossils demonstrate enlarged third inferior frontal convolution, increased brain size (750+ ml), and pronounced cerebral asymmetries.
- Modern human females show a larger posterior splenial portion of the corpus callosum compared to males.
Conclusions:
- Early hominid brain reorganization suggests a shift away from visual processing towards other cognitive functions.
- The evolution of the Homo lineage indicates significant increases in brain size, frontal lobe complexity, and lateralization, mirroring modern humans.
- Sexual dimorphism in the corpus callosum may reflect ancestral selection pressures favoring complementary social behaviors and a division of labor for offspring care.