Kissing is so common though we rarely ask why humans touch 【M1】______ their lips together

to show affection. One obvious answer is that it feels good. Densely packed nerve endings make your lips some of the most acutely sensitive regions of your entire body, and a few 【M2】______ things get them more riled up than a kiss. But where in humanitys evolutionary history putting our faces together come to be regarded 【M3】______ as a display of lust, care, friendship and love？ One of the most compelling hypotheses surroundings the 【M4】______ emergence of kissing in humans and kiss-like behavior. in other species are tied to the widespread practice of passing pre-chewed or 【M5】______ regurgitated food from the mouth of one animal to another. Birds do it. Chimps do it. Many humans even do it. The pass of food from 【M6】______ one creature to another is certainly an intimate form. of interaction. Though this behavior. can be regarded as altruistic is debatable, but 【M7】______ the fact that caring for ones young and securing a mate are both crucial to an organisms ability to pass its genes on subsequent 【M8】______ generations supports the argument that this behavior. would be evolutionarily encouraged. The science of kissing is a fascinated thing to think about and 【M9】______ Philematology(the science and study of kissing)is becoming an increasingly popular area of study, for researchers strive to sort out 【M10】______ the mysteries of love and attraction. Though plenty of unanswered questions remain, perhaps its sufficient to say that kissing remains an excellent and exciting human pastime.

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