Monkeys Like Full Red Lips, Too In snub-nosed monkeys, male lips plump up and redden as they age, likely to signify reproductive availability and social status. Maris Fessenden - Former correspondent.

Plump red lips have long been a symbol of sexuality, and not just for humans. For snub-nosed monkeys in China, lip colour indicates mating status, and it's males who flaunt a scarlet pout.