Darwin’s road not taken: white sclera, shared intentionality, niche construction, predator fear, teams and Homo origins

Abstract

Palaeoanthropologists have yet to pinpoint how Homo evolved from Australopithecus. I propose niche construction ending predator ambush and stalking attacks, white sclera, and ultrafast team cognition were key.Human white sclera allows the quick, distant detection of line-of-sight. This is unique. In other primates, predators eliminate conspicuous-eyed individuals. Consequently, nonhuman primates have coloured sclera, hiding gaze direction broadcasting. Recognizing line-of-sight’s split-second changes from a distance enables the ultrafast detection of attention shifts that support intercoupling cognitions (cognitive alignment, shared intentionality, and split-second coordination). Under certain conditions, such split-second coordinated teams can niche-construct predator-shunning safe habitats. Once shunning replaces hunting, it stops white sclera targeting, allowing it to persist.Constructing predator-safe habitats ended the “landscape of fear” that limited Australopithecus foraging, health, and cognitive/cultural development. Once shunned and freed from fear, these safe habitats allowed previously “wheel-clamped” cognitive potentials, including social learning, to flourish, revolutionizing hominin capacity for cultural evolution and cumulative culture. Thus, predator-safe niche construction transfigured Australopithecus’s phenotype into Homo. White-eyed australopiths, I argue, were the first humans.Significance Statement: The prevailing view is that genetic changes initiated the emergence of the human genus Homo. However, research on predator fear in songbirds and capuchin monkeys, along with its negative effects on social learning and cultural transmission, points to a non-genetic alternative. In this account, Homo arose when a group of Australopithecus found a way to gain predator shunning, not attack, freeing them from constant predation fear. Ending predator fear unlocked previously “wheel-clamped” cognitive and cultural potentials, triggering a phenotypic change dividing humans from other hominids. Critically, a plausible mechanism must have enabled Homo to achieve predator shunning to end its predation. A comprehensive review provides a compelling argument that such a mechanism did indeed exist and that its past occurrence can be empirically established. The proposed mechanism centres on two often-overlooked human traits: the conspicuous direction of our line-of-sight due to white sclera and our unique ability for split-second team coordination. The proposal posits that Homo emerged when white-sclera-eyed Australopithecus used their conspicuous line-of-sight to split-second coordinate as teams to get predators to shun them. This perspective challenges dominant genetic assumptions and identifies unexplored avenues to research human origins.