Just one thing. Even in historic times not all humans loved to kiss. Far from arising millions of years in the past, kissing seems to have arisen no earlier than 40,000 years ago, when modern humans began to enter northern Eurasia.

So concludes a recent cross-cultural study:

We found only 77 out of 168 (46%) cultures in which the romantic-sexual kiss was present. Significantly, no ethnographer working with Sub-Saharan African, New Guinea, or Amazonian foragers or horticulturalists reported having witnessed any occasion in which their study populations engaged in a romantic-sexual kiss. However, kissing appears to be nearly ubiquitous among 9 of the 11 foragers living in Circum-Arctic region (i.e., northern Asia and North America). The concentration of kissing among Circum-Arctic foragers, for which we do not have a satisfactory explanation other than invoking cultural diffusion, stands in stark contrast to its equally striking absence among foragers in other cultural regions.(Jankowiak et al., 2015)

This is not the first study to deny the universality of kissing, although scholars have tended to place its origin in the civilizations of the Mediterranean, the Middle East, and South Asia (Hawley, 2007; Hopkins, 1907).