Year: 2026
Type: preprint
Abstract: Paleoanthropology and archaeology employ various proxy measures of hominin cognition, including endocranial volume, the complexity of material culture, or encephalization quotients (EQ). Competing scenarios of hominin encephalization contrast gradual anagenetic change with punctuated models linked to speciation events and major technological innovations. Here, we employ improved estimates of EQ with increased spatiotemporal resolution, including a novel paleodeme approach, and examine their relationship with technological complexity. We found no substantial increase in hominin encephalization associated with the earliest stone tool technologies, the origin of our genus, or the onset of the Acheulean. Instead, segmented regression analysis identified a major breakpoint in encephalization at ~ 1.2–0.7 Mya and another inflection point at ~ 0.1 Mya. Measures of technological complexity correlate highly with EQ, demonstrating a tight, though late, integration of encephalization with cultural evolution. Exponential increases in relative brain size emerge only after the onset of the Middle Paleolithic/Middle Stone Age, coinciding with a marked acceleration in both the diversity and pace of cultural innovation during the Late Pleistocene. Our findings support a model of late, stepwise encephalization co-evolving with cumulative cultural complexity. Significance statement Our understanding of human evolution has long assumed that larger brains evolved gradually alongside the earliest stone tools and major technological innovations. We overturn this view by showing that substantial increases in relative brain size occurred much later than previously thought, characterized by a stepwise pattern that coincided with accelerating cultural innovation during the Middle to Late Pleistocene. These findings demonstrate that the evolution of larger brains and increasingly complex culture became tightly coupled only late in human history. This offers a revised biocultural framework for understanding the emergence of modern humans, proving that early technological milestones did not drive initial brain expansion, but that biology and culture later formed an accelerating, co-evolutionary feedback loop.
Source: Research Square
Language: English
Subfield: Anthropology
Field: Social Sciences
Domain: Social Sciences
Open Access status: green
Awards: G1392872459, G736697540
OpenAlex ID: W7205007940