Humans became social rather that solitary creatures when they stopped being nocturnal and became active during the day, British researchers say. Oxford University researchers say primates were originally solitary creatures that lived alone and foraged by night but millions of years ago they began moving around in daylight, which put them at greater risk of predators so they quickly formed groups to reduce their chances of being attacked, The Daily Telegraph reported. The researchers studied groups of living primates as well as the evolutionary relationships of 217 other primate species to discover how social behavior developed. Unlike other primates, they said, humans are flexible enough to adapt to a range of social settings and a number of social groupings such as nuclear families, extended families and monogamous and polygamous relationships. \"This flexibility in the human lineage has not evolved to anything like this level in other primates,\" study leader Suzanne Shultz said. \"Our findings support previous studies that suggest that more brain power is needed for groups that have a more complicated social life.\" The study was published in the journal Nature.