Mid-Latitude Seasonal Oscillation Hypothesis: A Downscaled Reinterpretation of the Recent African Origin Model and the Origins of Behavioral Modernity

The Recent African Origin (RAO) model has been highly successful in explaining human genetic diversity and dispersal patterns in low-latitude tropical regions. However, when simplified into a “complete replacement” narrative and uncritically applied to mid-latitude Eurasia (35°–40°N), it faces tensions with fossil records, lithic technological continuity, and paleoclimatic reconstructions. This paper does not reject the RAO model but downscales it to a “low-latitude tropical diffusion system” and proposes a parallel “Mid-Latitude Seasonal Oscillation Hypothesis.” Based on high-resolution Chinese loess records — particularly the 20 Dansgaard-Oeschger events and 6 Heinrich events documented by Guan et al. (2007) demonstrating millennial‑centennial scale rapid climate fluctuations — the continuous hominin fossil and cultural sequence in East Asia (35°–40°N) from the Early Pleistocene to the Late Pleistocene, the persistent phenotypic continuity of shovel-shaped incisors and the Inca bone, and proteomic/genomic evidence of indirect molecular continuity (Welker et al., 2026 online first; Fu et al., 2020; Mao et al., 2021), we argue that high-frequency glacial-interglacial seasonal oscillations — rather than low-latitude constant warmth — selected for behavioral flexibility, broad-spectrum diets, long-distance mobility, and symbolic thinking, the core elements of behavioral modernity. Behavioral modernity may have emerged independently, convergently, or in parallel in different refugia (East Asia, the Levant) along the 35°–40°N latitudinal belt and became fully integrated after admixture with low-latitude populations in the Late Pleistocene. This hypothesis is falsifiable: if continuous behavioral modern remains are discovered outside the 35°–40°N belt (e.g., in low-latitude Africa) with dates demonstrably earlier than the earliest record of the East Asian mid-latitude refugia, the hypothesis would be falsified. The hypothesis awaits testing by ancient DNA, submerged shelf archaeology, numerical modeling, and cross-regional comparison.