Touching heads is a uniquely human emotional expression that does not occur in nonhuman primates.[citation needed] All races, age groups and sexes of humankind interpret this behavior as an expression of positive emotions, such as love—including brotherly love, friendship etc.

A bodily expression of positive emotions

It is absent in other apes, though they tend to use the same bodily expressions of emotions like humans.[1] A 2012 study claimed that this behavior likely evolved in humans to share head lice among friends and relatives. Head lice infestations might serve as a protection against body lice by inducing cross-resistance. This can be adaptive because only the latter type of lice transmit potentially lethal human pathogens.[2]

References edit

  1. ^ Darwin Charles (1998) The Expression of the Emotions in Man and Animals, 3rd edn, London: Harper Collins.
  2. ^ Rozsa L, Apari P (2012). "Why infest the loved ones – inherent human behaviour indicates former mutualism with head lice" (PDF). Parasitology. 139: 696–700. doi:10.1017/s0031182012000017. PMID 22309598.