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The Ādam Paradox Hypothesis 60
SRGAP2C: Extending the Window of Learning
The third candidate, SRGAP2C, did not add a new capacity but extended the
time to cultivate one. Around 2.4 million years ago, a duplication created
SRGAP2C, which inhibits its ancestral counterpart SRGAP2A. The result was
delayed dendritic spine maturation, yielding more numerous and longer-lasting
spines. Charrier et al. (2012) concluded: “Inhibition of ancestral SRGAP2 by human-
specific paralogs induces neoteny in spine maturation.
”
This duplication extended cortical plasticity, prolonging the learning window—
what paleoanthropologists call neoteny. Fossati et al. (2016)
confirmed: “SRGAP2C reshaped excitatory–inhibitory balance, prolonging the learning
window.
”
But timing again reveals the paradox. SRGAP2C arose ~2.4 million years ago,
shaping the brains of Homo erectus long before Homo sapiens. As Dennis et
al. (2012) noted: “Duplications of SRGAP2 occurred millions of years before modern
humans.
” Yet symbolic traditions remained unstable. Acheulean handaxes
endured for a million years with little cumulative change. Plasticity existed, but
the score was unwritten.
Archaeological echoes align. From early ornaments to engraved objects,
innovations arose only to vanish. The stage time was extended, but the
performance had not begun.
In the APH framework, SRGAP2C represents the deepest preparation. The
clay was long kneaded. But the true ignition—the firing of the clay—came only
with Adam’s activation, when extended plasticity was coupled with stable
symbolic continuity.
The Archaeological Mirror
FOXP2 explains vocal learning and Neanderthal sparks. HARs explain cortical
refinements and engraved ochres. SRGAP2C explains extended plasticity and
repeated but unstable innovations. Together they form a pattern: capacity
without continuity.
As Chris Stringer observed: “Modern humans were cognitively ready long before they
behaved that way.
” (Stringer, 2012). The genome was prepared, the clay refined,
but the firing absent. Only after ~70kya do we see global, unbroken traditions
of symbolism—evidence that the system was finally activated.