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The Ādam Paradox Hypothesis 128
The Post-70,000-Year Expansion
Something changed after ~70,000 years ago. Genetic reconstructions based on
whole-genome sequences show a sharp increase in effective population size
following the bottleneck (Li & Durbin, 2011). The demographic curve, flat for
hundreds of thousands of years, suddenly rises. This is not a subtle trend — it
is a sharp inflection.
Key markers tell the story:
mtDNA L3 lineage: All non-African maternal lineages trace back to this
single root, dated to ~70 ka.
Y-chromosomal CT lineage: Ancestral to all non-African paternal lines, it
also coalesces in the same timeframe.
Serial founder effects: As humans expanded, genetic diversity decreased
with distance from Africa, a pattern expected only under rapid dispersal.
David Reich, synthesizing this evidence, states:
“When we examine DNA from populations worldwide, the overwhelming evidence is that all
non-Africans descend from a single expansion out of Africa, beginning around 70,000 years
ago.
” (Reich, 2018, p. 45)
The genomic evidence mirrors the archaeological explosion that follows.
By 65–50 ka, humans had reached Australia, requiring sea crossings of
dozens of kilometers. This is not accidental drift; it demands planned
seafaring and navigation.
By 45 ka, Homo sapiens entered Europe, where they carved ivory figurines
and painted animals with dynamic realism on cave walls such as Chauvet
and Lascaux.
By 40 ka, they were in Siberia, adapting to cold climates with tailored
clothing and complex shelters.
By 15 ka, they had crossed into the Americas, filling the last major
habitable continent.