What is the evolutionary advantage of big lips and small lips?

What conditions made nature select for big lips?What is the evolutionary advantage of big lips and small lips?
Big lips, means a better kisser = More mating opportunities!





Small lips are more practical in a cold or windy environment. There's less chance for freezing/frostbite/chapped lips.





Most chimps have relatively large lips, and they evolved in a jungle environment which tends to be more shaded than coastal, desert or savanna regions!What is the evolutionary advantage of big lips and small lips?
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I know you're talking about modern humans here...but, think about the early humans with big lips...the advantage of those are in obtaining food...scooping, tearing, reaching....why not prehensile lips along with the term prehensile tails?


Once mankind did not have to forage like that, the lips became 'ordinary'.


The subject of sunburn and freezing comes in....the weather conditions in prehistoric Africa and the other home areas from migration were much cooler than at present....the Sahara was part of a huge lake. Large lips would not have burned that easily. And thin lips in colder climates would not have been frostbitten as easily.
Big lips are very pretty and a better sexual signal, but in a cold environment they'll get badly chapped, and maybe even frostbite in severe conditions. Thin Caucasian lips are adapted to cold weather.