Whatever may have been the original reason why humans acquired control over fire, it seems that it came to play a central role in two crucial respects. First, it effectively extended the active day . Monkeys and apes are forced to be inactive at night because their relatively poor nighttime vision renders them (and us) especially susceptible to predators at night (all of the major predators of terrestrial primates, including humans, are nocturnal). Fire potentially allowed us to remain active into the evening, thus adding as much as 4 h to the working day. Second, it provided a venue in which social interaction, and pretty much only social interaction, could take place. Those extra evening hours could not be used for foraging, and the lighting isn’t that good for making tools; although the evening can be used for cooking and eating, these only take up the whole evening on very special occasions (feasts). There is considerable “empty” time that can only be devoted to conversation (dyadic bonding) and storytelling (communal bonding) or other social bonding activities such as singing and dancing.
Robin.I.M. Dumbar, How Conversations Round Campfires Came To Be