2021 Study Says Human Vermilion Border Evolved Uniquely, With 3 Main Theories
Updated
Updated · Forbes · Aug 23
2021 Study Says Human Vermilion Border Evolved Uniquely, With 3 Main Theories
1 articles · Updated · Forbes · Aug 23
Summary
A 2021 anatomy study found the lip vermilion border—the pink-red band where inner mouth tissue turns outward—is unique to Homo sapiens among living hominids.
That exposed redness comes from unusually thin lip tissue and visible blood vessels, not pigment; the same design leaves lips without oil glands, making them prone to drying, chapping and sun damage.
Three leading explanations compete: infant feeding, speech production and social or sexual signaling, with the last aimed most directly at why human lips stay visibly red.
A 2012 monkey lip-smacking study and 2017 sensory-cortex research suggest lips sit at the intersection of speech, touch and early infant exploration rather than serving a single evolutionary purpose.
A 2015 survey of 168 cultures undercuts the idea that lips evolved for kissing, reinforcing that the feature likely reflects multiple pressures on the human face.