He added, "The article combines the use of some new technology with traditional approaches to learn that the snub-nosed monkeys, traditionally considered diurnal, may show some nocturnal activity under certain circumstances. Their proposition that this flexibility in activity patterns may be associated to the temperate environment is reasonable."
Humans, of course, fall into the day and/or night-living primate category too. This is often a survival tactic, as people with late shift jobs could attest. It's possible that our distant relatives were 24-7 individuals as well.
"It is difficult to infer a full range of behavior from fossilized species, but I would not be surprised if some of our earliest human ancestors were regular night owls," Tan said. "They would, under certain environmental conditions, be up at night. Party anyone?"