As Homo erectus roamed the expansive African savannas, a significant evolutionary shift unfolded in our lineage: a visibly reduced coat of body hair. This change likely enhanced sweat-based cooling, allowing early humans to shed heat efficiently under the intense sun during long bouts of walking, running, hunting, and foraging. In open landscapes where endurance mattered more than bursts of speed, staying cool became a survival advantage.

Importantly, this shift did not involve losing hair follicles or inventing a new body pattern. The basic map of hair follicles across the human body is ancient, shared with other great apes, and likely predates the human–chimpanzee split over seven million years ago. What changed in Homo erectus was how those follicles behaved—producing finer, shorter, and less pigmented hair across most of the body. Humans did not become hairless; they became better at heat management.

While this transition marked a clear trend toward the hairiness levels seen in modern humans, variation almost certainly persisted. Some individuals may have retained slightly thicker or more visible body hair, offering modest insulation in cooler regions or during seasonal shifts. As with many human traits, natural diversity remained the rule, not the exception.

Skin Color Variety: Each time members of the genus Homo spread into new environments, the melanin-regulation systems shared by all primates responded accordingly. The following image imagines our ancestors across the diverse climates they had reached by about 1.2 million years ago.