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The Ādam Paradox Hypothesis 13
Strand Three: Brains — Volume, Shape, and Globularity
Size Arrives Early
By ~200 ka, humans already had brains averaging 1,350–1,500 cc—equal to
or larger than today
’s humans (Rightmire, 2004). This undercuts any simple
link between brain size and symbolic culture.
Tattersall put it sharply:
“Large brains were around for a long time before
being put to the symbolic uses that define us”(Tattersall, 2012, p. 191).
Shape Arrives Late
Recent work shows that what changed was not just size, but shape.
Neubauer, Hublin, and Gunz (2018) studied fossil endocasts and found that
early Homo sapiens had long, low skulls. The fully globular braincase—
associated with expanded parietal and cerebellar regions—emerged gradually
between 200–35 ka.
Neubauer explained:
“Brain shape evolved within Homo sapiens after its
origin. Globularization may reflect changes in neural connectivity important
for language and social cognition” (Neubauer et al., 2018, p. 2).
Table 2.2 — Brain Development: Volume vs. Shape vs. Symbolis
Takeaway: Big brains alone did not trigger symbols. The cognitive
architecture—reflected in globularity—evolved later, synchronizing with the
ignition of symbolism.