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The Ādam Paradox Hypothesis 59
HAR1 and the Human-Accelerated Regions: Developmental Whispers
If FOXP2 was the conductor, HAR1 was the whisper shaping the stage. HAR1
is a noncoding RNA expressed in Cajal-Retzius neurons during fetal
development. These neurons secrete reelin, guiding cortical layering. Pollard et
al. (2006) observed: “HAR1 is expressed in Cajal-Retzius neurons, co-localized with
reelin, crucial for cortical layering.
”
HAR1 is one among thousands of Human-Accelerated Regions (HARs)—
DNA sequences that evolved unusually rapidly after the human–chimp split.
Many act as enhancers in brain development. Capra et al. (2013)
concluded: “Many HARs are developmental enhancers active in the human cortex,
especially in neural progenitors.
”
HARs are not genes but switches. They adjust the timing, strength, and location
of gene expression. Reilly et al. (2015) found that HAR enhancers significantly
alter promoter activity during corticogenesis. This subtle tuning can produce
threshold effects: small adjustments across networks yield large shifts in
developmental outcomes.
The archaeological record mirrors these whispers. At Blombos Cave (~100–
75kya), ochres were deliberately engraved with cross-hatch patterns
(Henshilwood et al., 2002). At Qafzeh (~100kya), shells were perforated and
strung as beads (d’Errico et al., 2003). At Diepkloof (>55kya), ostrich eggshells
were engraved with repeated motifs (Texier et al., 2010).
Ian Tattersall (2009) reflected on this problem: “The issue is not capacity but
continuity: symbolic sparks appear, then vanish, until the explosion after ~70,000 years
ago.
” HARs had prepared the cortex, but without activation, their whispers
remained ephemeral.
The APH interprets HARs as the fine brushstrokes of preparation. They
shaped the clay into a form capable of resonance. Adam marked the moment
when these whispers became coherent speech, stabilizing symbolic culture.