That sounds a little odd, but plausible I guess. But that would have had to been a very early development, as the lips are certainly a strongly erogenous zone and closely related to the erotic (though that might be more of a social development rather than biological one, as it only appears during the period of sexual maturation and may well be a natural development to the pleasure a kiss gives).

Yes, stuff like this is always very interesting. I'm a real fan of Stephen Jay Gould's writing on popular science, as you can always find little gems like this.

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